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Physical Activity Guidelines Advisory Committee Report
Part G. Section 6: Functional Health
List of Figures
Introduction
This chapter reviews evidence related to the effects of physical
activity on improving functional health and/or preventing disability in
middle-aged and older adults. Background information is provided, followed by
an assessment of the evidence related to 3 questions about possible health
benefits of physical activity.
Conceptual Model and Terminology
The term "disability" has been defined in several different ways in
scientific models of disability (1;2).
In this chapter, "disability" is used as an umbrella term to refer to deficits
in overall health that affects a person's ability to do tasks of everyday life.
That is, disability is the other side of the coin of health a reasonably
(though not perfectly) healthy person has a lot of health, but also a little
disability. Measures of physiologic impairment, functional limitations, and
role limitations assess the status of basic aspects of the disablement
process.
A thorough discussion of the existing conceptual frameworks used to
model and describe the disablement process is beyond the scope of this
discussion. However, 3 basic concepts, which are included in several models of
disability, are often used when discussing this process, and they provided a
conceptual foundation for the Functional Health subcommittee's evidence review
and deliberations (1;2).
- The capacity of the physiologic systems of the body (which
depends upon the status of physiological functions and anatomical structures).
We refer to this concept as "physiologic capacity," and loss of physiologic
capacity is referred to as "physiologic limitation." Examples of physiologic
capacity relevant to this section include measures of physical fitness such as
aerobic power (VO2max) and muscle strength. A recent review by
Paterson and colleagues provides evidence that physical activity programs
improve physiologic capacity in older adults (3).
- The capacity of a person to perform a task, activity, or behavior
in a controlled environment that neither enhances nor impairs behavioral
abilities. We refer to this concept as "functional ability," and loss of
functional ability is referred to as "functional limitations." Examples of
functional abilities include ability to walk at a normal speed on a flat
surface, and ability to climb a typical flight of stairs.
- The capacity of a person to perform a task, activity, or behavior
in his or her actual environment, so as to fulfill the roles a person assumes
in life. We refer to this concept as "role ability," and loss of role
ability is referred to as "role limitations." We live in environments that
contain physical and social factors that facilitate or impair ability to
perform roles. A person who cannot walk several hundred meters cannot perform
the task of grocery shopping in a large grocery store and fulfill the role of
family food shopper. But he or she can perform the task in a small store or in
a store with motorized carts. Measures of role performance include activities
of daily living (ADL) and instrumental activities of daily living (IADL)
scales.
Another term that is key to this chapter and to the health of older
adults is "fall." A fall is defined as unintentionally coming to rest on the
ground, floor, or other level lower than one's starting point (4). Falls in older adults can be classified into 3 main
groups. About 20% of falls result from an external precipitant, such as being
tripped up by a large, rambunctious dog while out for a walk. This type of fall
is simply the consequence of an active lifestyle, and not the result of a
disablement process. Another 20% of falls are due to a single identifiable
cause, such as a drug-related syncope, stroke, or Parkinson's disease. Adults
with such falls require diagnosis and specific therapy directed at the single
major cause. The majority of falls, though, result from multiple etiological or
causative factors interacting that put older adults at risk of falling. This
chapter is concerned with the prevention of this type of fall.
Characteristically, falls of this type have only minor provocation, such as
tripping on a step or loose rug. Epidemiologic studies suggest that decline in
muscular strength, speed of reaction, and balance are key factors in fall risk
(4;5). It is well documented that older
adults with functional limitations are at increased risk for falls and their
sequelae, such as fractures of the wrist and hip. Hence, these falls are
regarded as a result of the disablement process in older adults.
Functional Health in Middle-Aged and Older
Adults
The etiology of disability differs strongly by age. Disease-related
disability affecting middle-aged and older adults accompanies well-known,
common diseases, such as cardiovascular disease, depression, diabetes, stroke,
arthritis, and dementia (6;7). The
effects of such diseases on disability are compounded by loss of physiologic
capacity due to biologic aging, such as decline in aerobic capacity, muscle
strength, and balance (8;9). The models
of disability in older adults involve concepts like frailty, where the
capacities of multiple physiologic systems are markedly reduced.
In contrast, disability in younger age groups is much less prevalent, is
much less likely to be due to such chronic diseases, and is not compounded by
declines associated with aging. It involves, for example, developmental
disabilities, genetic syndromes, and traumatic injuries. Because of the
difference in pathogenesis by age, it is appropriate to separate the evidence
review of disability in children and young adults from the evidence review in
older adults. This chapter reviews the evidence for older adults.
The Importance of Reducing Disability and
Falls in Older Adults
Older adults have the highest prevalence of disability (10) and falls (4) of any age group in the
population. Studies consistently show that the prevalence of both major
disability and falls increases with age, and is higher in women than men. As
the life expectancy of older Americans continues to increase, the burden of
disability in older populations is also expected to increase. The Medicare
Current Beneficiary Survey (MCBS) is particularly useful for characterizing
disability in older adults, as it includes persons living in the community and
persons living in long-term care facilities (11). In 2003,
the MCBS characterized mobility limitation as difficulty walking a quarter of a
mile. In men, the prevalence of mobility disability was 31% for those aged 65
to 74 years, 46% for those aged 75 to 84 years, and 69% for those aged 85 years
and older. Corresponding percentages in women were 42%, 57%, and 81% (11). In a community population aged 70 years and older,
around one third of people will fall in any 1 year (4). In
a recent US survey, approximately 5.8 million persons aged 65 or older fell in
the preceding 3-month period (12). Fall rates increase
with age and are higher in women than men. Fall-related injuries can have a
large adverse effect on functional ability in older adults and can sometimes
directly result in death (5;13-15).
Disabilities and falls have a significant impact on the ability of older
adults to live independently, and the treatment and management of disability
and falls in older adults consume enormous resources involving both medical
care and long-term care (16-18). One can hardly
overestimate the importance of independent living to quality of life in older
adults.
National surveys consistently show that older adults are the least
active age group of Americans. For example, national survey data from 2005 show
that an average of only 21% of people aged 65 years and older report meeting
recommended levels of physical activity, with women reporting slightly less
physical activity participation rates than men (19). A
recent national survey using an objective measure of physical activity
(accelerometers) suggests older adults may be substantially less active than
they report on questionnaires (20). If physical activity
prevents or delays disability, the majority of older Americans stand to
benefit.
Review of the Science
Overview of Questions Addressed
This chapter addresses 3 major questions:
- In middle-aged and older adults who do not have severe functional or
role limitations, does regular physical activity prevent or delay the onset of
substantial functional limitations and/or role limitations?
- In older adults, who have mild, moderate, or severe functional or
role limitations, does regular physical activity improve or maintain functional
ability and role ability with aging?
- In older adults who are at increased risk, does regular physical
activity reduce rates of falls and fall-related injuries?
Data Sources and Process Used To Answer
Questions
The Functional Health subcommittee used the Physical Activity
Guidelines for Americans Scientific Database as its primary source of
literature since 1995 to review all 3 questions (see Part F: Scientific Literature Search
Methodology, for a full description of the Database). The
subcommittee then used the reference lists from those papers as well as the
collective expertise of its members and consultants to identify additional
relevant publications, meta-analyses, and systematic reviews.
Question 1: In Middle-Aged and Older Adults
Who Do Not Have Severe Functional or Role Limitations, Does Regular Physical
Activity Prevent or Delay the Onset of Substantial Functional Limitations
and/or Role Limitations?
Conclusions
Strong, consistent observational evidence indicates that mid-life and
older adults who participate in regular physical activity have reduced risk of
moderate or severe functional limitations and role limitations. Active mid-life
and older individuals both men and women have approximately a 30%
lower risk of developing moderate or severe functional limitations or role
limitations compared with inactive individuals. The observational evidence of
benefit is strong for aerobic activity, but limited for other types of activity
(muscle-strengthening, balance, and flexibility activities). It should be noted
that no randomized controlled trials (RCTs) were available to answer Question
1.
Several important findings from the literature review support this
conclusion:
- The results were strongly consistent across studies;
- In studies with repeated measures of physical activity during
follow-up, adults who reported regular physical activity at all measurement
occasions were at lowest risk of functional limitations; and
- Studies that assessed change in physical activity over time reported
that change from lower levels of activity to higher levels of activity over
time was associated with reduced risk of limitations.
Introduction
The aging of the American population has led to large numbers of older
persons (aged 65 years and older), with a rapidly expanding proportion reaching
advanced old age (85 years and older), a category termed the oldest old (21). This population includes large numbers of older adults
who have no difficulty or only mild difficulty living independently in the
community (11;22). That is, such
older adults have no or mild functional limitations and role limitations.
Across the population, older adults strongly wish to avoid major functional
limitations and major role limitations that would lead to dependent living.
Hence, Question 1 asks a primary prevention question: Does physical activity
prevent or delay onset of moderate or severe functional limitations and/or role
limitations in middle-aged and older adults?
It is theoretically possible to answer this question using a large RCT.
The problem is that such trials are extremely difficult and expensive, and to
our knowledge such a study has never been done. Analogous to other primary
prevention studies regarding lifestyle, such as tobacco or nutrition,
information about prevention comes from observational studies, including both
prospective and retrospective cohort studies. Cohort studies of physical
activity and disability generally use one of 2 approaches. Some studies use a
dichotomous measure of disability (e.g., presence or absence of inability to
walk 400 meters) as an outcome, and compare rates of incident disability in
people with different levels of physical activity. Other studies use a
continuous measure of disability (e.g., the Health Assessment
Questionnaire-Disability Index) and compare the rate of decline in people with
different levels of physical activity (23).
Conceptually, the cohort studies can also be divided into 2 types based
upon the population they recruit. A "pure" primary prevention study would
include adults and older adults with either no limitations or mild limitations
at baseline, and assess whether physical activity prevents or delays onset of
moderate or severe limitations. The other approach is to assess whether
physical activity prevents severe limitations in a population that includes
adults with no, mild, or moderate limitations. Both types of studies exist and
were used to address the question.
Given decades of research showing that physical activity in healthy
adults (including healthy older adults) improves physiologic capacity and hence
functional ability (e.g., ability to walk a mile), one might ask, "Doesn't this
mean physical activity prevents disability?" A response to this question is
that the pathogenesis of decline in older adults is complex, with many causal
factors and etiologic pathways involving a large number of diseases. The
improvement in physical fitness and physical performance is one mechanism by
which physical activity can prevent decline. The reduction in the incidence of
chronic diseases (e.g., ischemic heart disease, depression, type 2 diabetes) is
another mechanism by which physical activity can prevent decline. However, a
more meaningful question is whether the net effect of physical activity across
all etiologic pathways (only some of which are influenced by physical activity)
is sufficient to have a meaningful effect size on the incidence (or rate) of
moderate or severe limitations in older adults.
Rationale
The Scientific Database was the primary source of studies for review to
answer Question 1. Additional research studies (not in the Database) were
identified by review of reference lists of published studies. The subcommittee
members and consultants also identified papers for consideration based upon
their expertise and knowledge of the field. Information from the articles was
systematically abstracted and summarized in the tables and figures accompanying
the chapter. The search of studies was limited to studies published between
1995 and 2007. In addition, a supplemental PubMed search was performed to find
reviews of the literature between 1990 and 2007.
Specifically, we sought only cohort studies (including both prospective
and retrospective studies) that measured the physical activity level of
participants at baseline as the exposure variable, and assessed either
functional limitations or role limitations during follow-up as an outcome
variable. As indicated above, these studies were of 2 types: (1) the study
sample at baseline included adults with only no or mild functional limitations
or role limitations; and (2) the study sample at baseline included adults with
none, mild, or moderate functional limitations or role limitations. We regarded
ADL limitation as an indicator of severe role limitations. Studies that
examined only the relation between physical fitness and risk of functional/role
limitations were not included in the review.
Twenty-eight prospective cohort studies addressed the relation between
physical activity and risk of functional limitations and role limitations (23-50). Table G6.A1
provides a summary of the studies. Almost all these prospective cohort studies
reported that active adults had a lower incidence of functional and role
limitations. Only 4 studies did not find a significant relation between
physical activity and risk of functional or role limitations (26;31;43;48). However, statistical power was limited in some of these
negative studies, as illustrated by a study where the confidence interval (CI)
on one adjusted odds ratio of .91 ranged from .22 to 3.70 (31) and a study where a 23% reduction in risk was not
statistically significant (48). Both of the other two
studies were not significant at the 0.05 level, but were very close (26;43).
The findings were consistent across different types of outcome measures
that included measures of functional limitations as well as role limitations,
including measures of mobility, ADL, IADL, measures of overall ("global")
functional and role limitations, and occupational status. In studies that used
an odds ratio or hazard ratio to quantify the risk reduction, 19 studies
reported at least a 30% lower risk (a ratio or 0.70 or less) when comparing the
most active to the least active subgroups of adults. Studies with repeated
assessments of physical activity consistently reported that adults who were
regularly active during follow-up had the lowest risk of disability (30;32;34;36). The 2 studies that assessed change in physical activity
level during follow-up consistently reported that adults who switched from
inactive to active during follow-up had a lower risk of limitations than adults
who remained inactive (23;48). One
study also measured aerobic fitness (using a treadmill test) (32). Although both physical activity and aerobic fitness were
each associated with significantly reduced risk of functional limitations over
time for both men and women, the aerobic fitness provided even greater risk
reduction (OR 0.30) (32).
Dose-Response Pattern
The findings from the prospective cohort studies support a dose-response
effect, where greater amounts of physical activity were associated with lower
risk of limitations. Figure G6.1 shows data from
prospective cohort studies with measures of mobility limitations.
Figure G6.2 shows data from studies with ADL,
IADL, and/or global measures. When studies reported a statistical test of trend
across categories of physical activity, the trend was statistically significant
(29;30;32;34;36;37) with one
exception where P=0.08 (48).
Because of the diversity in methods used to assess physical activity, it
was not possible to reach a conclusion about the amount of risk reduction that
occurs from a specific amount of physical activity. However, a reasonable
conclusion is that adults who do moderate amounts of activity for the purposes
of reducing risk of common chronic diseases also would reduce risk of
functional and role limitations.
Generalizability of Findings
The research supports the conclusion that the findings are widely
applicable to older adults. Some studies, such as the Longitudinal Study of
Aging and the Health and Retirement Study, enrolled nationally representative
samples (29;35;36). Many others involved a systematic sample of a specific
geographic area within a country, such as a city. About half the prospective
cohort studies enrolled samples that included adults aged 85 years and older,
thereby providing evidence that the oldest old benefit from physical activity
(although most did not analyze data separately for that age group). Most
studies enrolled both men and women. Studies that did separate analyses for men
and women commonly reported significant benefits for both (28;32;37;40;46). Almost all studies were done in
the United States or Europe, though one study (50) was
from Taiwan and one study (42) was from Israel. Although
the studies did not directly compare the effect of physical activity among
different race/ethnic groups, no evidence suggested that effects of physical
activity would not occur in all race/ethnic groups. It could not always be
ascertained with certainty, but it appeared about half the studies enrolled
adults with no or mild limitations, and about half the studies enrolled adults
with no, mild, or moderate limitations. We located only one study that included
objective measures of both physical activity and of functional limitations (25). Four studies measured some outcome related to physical
fitness or functional ability in addition to physical activity and functional
limitations (25;32;38;40).
Figure G6.1. Prospective Cohort Studies
With Measurement of Mobility Limitations
Legend: The figure shows the reported odds ratio for
each category of physical activity (PA), with the lowest category of PA
assigned as the referent category. For example, the Wannamethee study had four
categories of PA, with category 1 (the referent) assigned to those with the
lowest level of PA, category 4 assigned to those with the highest activity
level, with all categories forming an ordinal scale.
Figure G6.1. Data Points
|
Referent |
2 |
3 |
4 |
5 |
Wannamethee et al., 2005 (48) |
1 |
0.9 |
0.88 |
0.77 |
|
Ostbye et al., 2002 (36) |
1 |
0.53 |
0.35 |
0.21 |
|
He et al., 2004 ("Vigorous PA") (29) |
1 |
0.83 |
0.73 |
0.58 |
0.57 |
Patel et al., 2006 Men (37) |
1 |
0.37 |
0.23 |
|
|
Patel et al., 2006 Women (37) |
1 |
0.69 |
0.7 |
|
|
Visser et al., 2005 Men (46) |
1 |
0.7 |
0.48 |
|
|
Visser et al., 2005 Women (46) |
1 |
0.73 |
0.51 |
|
|
Miller et al., 2000 (35) |
1 |
0.68 |
|
|
|
Schroll et al., 1997 Men (40) |
1 |
0.24 |
|
|
|
Schroll et al., 1997 Women (40) |
1 |
0.23 |
|
|
|
Kujala et al., 1999 (33) |
1 |
0.46 |
|
|
|
Christensen et al., 2006 (26) |
1 |
0.18 |
|
|
|
Figure G6.2. Prospective Cohort Studies
With Measures of ADL, IADL, and Global Outcomes
Legend: ADL, activities of daily living; IADL,
instrumental activities of daily living. The figure shows the reported odds
ratio for each category of physical activity, with the lowest category of
physical activity assigned as the referent category. For example, the Huang
study had three categories of physical activity, with category 1 (the referent)
assigned to those with the lowest level of physical activity, category 3
assigned to those with the highest activity level, with all categories forming
an ordinal scale.
Figure G6.2. Data Points
|
Referent |
2 |
3 |
4 |
5 |
Huang et al., 1998 Men (32) |
1 |
0.7 |
0.5 |
|
|
Huang et al., 1998 Women (32) |
1 |
0.7 |
0.7 |
|
|
Hillsdon et al., 2005 (30) |
1 |
0.91 |
0.63 |
|
|
Leveille et al., 1999 (34) |
1 |
0.67 |
0.53 |
|
|
Ostbye et al., 2002 (ADL) (36) |
1 |
0.53 |
0.44 |
0.28 |
|
Ostbye et al., 2002 (Global) (36) |
1 |
0.51 |
0.46 |
0.25 |
|
Hirvensalo et al., 2000 Men (31) |
1 |
1.1 |
|
|
|
Hirvensalo et al., 2000 Women (31) |
1 |
0.85 |
|
|
|
Miller et al., 2000 (35) |
1 |
0.74 |
|
|
|
Haight et al., 2005 Men (28) |
1 |
0.63 |
|
|
|
Haight et al., 2005 Women (28) |
1 |
0.47 |
|
|
|
Strawbridge et al., 1996 (43) |
1 |
0.59 |
|
|
|
Backmand et al., 2006 (24) |
1 |
0.89 |
|
|
|
Ward et al., 1995 (49) |
1 |
0.61 |
|
|
|
Wu et al., 1999 (50) |
1 |
0.52 |
|
|
|
Stessman et al., 2002 (ADL) (42) |
1 |
0.23 |
|
|
|
Stessman et al., 2002 (IADL) (42) |
1 |
0.43 |
|
|
|
Limitations
The conclusions for Question 1 have several caveats. First, because all
of the studies in the evidence base were observational epidemiologic studies
with no RCTs, the data cannot prove causality of effect. Some concern exists
that the prospective cohort studies could not adequately adjust for confounders
and may have overestimated the effect. Healthy people are more physically
active than are people with health conditions, and adjusting for all health
status differences between physically active and sedentary persons is not
possible in these studies. However, the consistency of evidence does support a
cause-and-effect relation between physical activity and lower risk of
functional and role limitations. In addition, plausible biological mechanisms
demonstrated in RCTs exist for physical activity to improve
physiologic capacity (e.g., aerobic power, strength, balance) and functional
ability in older adults (see Question 2). These
are all important factors in the causal pathway toward disability.
Second, although evidence indicates that regular aerobic activity
prevents functional and role limitations, evidence of a beneficial effect of
muscle strengthening activities, balance activities, and flexibility activities
is insufficient. Two additionally reviewed studies analyzed measures of leg
strength, with one reporting that higher leg strength reduced risk of
limitations (51) and another essentially reporting no
association (40).
Third, although the literature provides sufficient evidence of a
dose-response effect (i.e., the more physical activity, the greater the
preventive effect), it is difficult to make statements about the amount of
physical activity required for substantial preventive effect. It was common for
studies to use simple measures of self-reported physical activity (e.g.,
frequency and duration of walking activities), but not to provide information
of the validity of the measurement method. All the studies but one (25) relied upon self-report measures of physical activity and
most used self-report measures of functional and role limitations. Additional
studies that use objective measures of physical activity and objective measures
of functional ability are needed.
Finally, data are insufficient to determine whether the preventive
benefits of physical activity differ by race or ethnic group. Some studies
enrolled representative samples of the US older adult population, but few
studies directly compare the effects of physical activity across race or ethnic
groups.
Question 2: In Older Adults Who Have Mild,
Moderate, or Severe Functional or Role Limitations, Does Regular Physical
Activity Improve or Maintain Functional Ability and Role Ability With
Aging?
Conclusions
Modest evidence indicates that regular physical activity in older adults
with existing functional limitations improves functional ability. Due to the
lack of well-designed intervention trials, only limited evidence is available
to conclude that physical activity in older adults with existing functional
limitations improves or maintains role ability with aging.
Most of the physical activity interventions included both aerobic
(especially walking) and muscle strengthening activities, with fewer
interventions using only a single type of activity. For this reason, most
evidence reflects a pattern of physical activity that involves periods of 30 to
90 minutes of moderate to vigorous physical activity, on 3 to 5 days per week,
in which most of this time is devoted to aerobic activity and muscle
strengthening activity and with a shorter amount of time spent on other forms
of activity, such as flexibility. When it was possible to determine the amount
of time spent just on aerobic activity (mostly walking), it usually varied from
60 minutes per week to 150 minutes per week. Because of low baseline fitness
levels in older adults, "relative intensity" should be used for determining
exercise intensity instead of absolute intensity. Evidence is limited that
physical activity levels less then described above provide some benefit.
Introduction
Some older adults already have functional limitations and role
limitations. However, prevention of further decline is still relevant for these
older adults and this is the focus of Question 2. In people with existing
diseases or limitations, concern always exists that the disease processes are
so advanced that they are difficult to influence. Question 2 can be thought of
as asking whether it is "too late" for people with existing limitations to
benefit from physical activity.
Both RCTs and observational studies have been conducted to address
Question 2. The RCTs address whether the rate of change ("decline") in
functional or role limitations differs between a control group and a physical
activity group. The observational studies and RCTs provide complementary
information, in that observational studies can address the effects of years of
regular physical activity (though residual confounding, resulting from
differences between people who choose to exercise versus those who do not that
cannot be fully adjusted for, is a threat to their validity), while few
existing randomized trials have studied more than 12 months of regular physical
activity (but randomization greatly reduces the risk of confounding).
Rationale
The sources of research studies was the same as for Question 1
studies published between 1995 and 2007, relying mainly on the Scientific
Database for locating the studies. The Functional Health subcommittee included
only RCTs and prospective cohort trails that included adults aged 60 years or
older with functional limitations and role limitations and recruitment of 25
subjects or more. We excluded papers if they focused on a specific disease
(e.g., dementia) or subjects who were hospitalized at the start of the trial.
We excluded studies in healthy adults with no limitations. We included only
studies whose primary purpose was to determine whether physical activity
affected functional health. Some of these studies recruited only participants
with mild to moderate functional limitations, and some recruited a mix of
participants with no, mild, or moderate limitations. Because of incomplete
information on functional ability in participants in many studies, we could not
always ascertain the range of functional ability of the study sample. It should
be noted that the subcommittee did not review studies focusing on arthritis and
functional health, as this topic is covered in Part G. Section 5: Musculoskeletal
Health.
Fourteen trials were reviewed to answer this question: 12 RCTs (52-63) (Table G6.A2)
and 2 prospective cohort studies (31;41) In addition, 4 review papers considered this issue (64-67). The sample size in the RCTs ranged from 39 to 486
subjects. The prospective cohort studies had samples of slightly more than
1,000 subjects (31;41). All of the
subjects in these studies were older adults aged 65 years or older. All of the
RCTs recruited subjects who were sedentary. The baseline health status of the
subjects varied. Eight of the RCTs recruited people with functional limitations
(52;55;57;58;60-63); 4 of the trials recruited
subjects both with and without functional limitations (53;54;56;59). In most of the studies, the subjects were older adults
who lived in the community. Only one study enrolled adults living in a
residential-care facility (55).
All but one of the randomized trials used multimodal interventions that
included a mixture of aerobic activity, balance training, strength training,
and/or physical therapy guided functional training. One study used a single
intervention of muscle-strengthening or power activities (60). The format of the interventions varied. Some of the
interventions were supervised group sessions held in community settings, some
took place in the home (supervised or unsupervised), and still others were a
mixture of the two. The frequency and duration of the interventions also
varied, though the majority of interventions took place 3 to 5 days per week
and lasted between 40 and 90 minutes. The length of the interventions ranged
from 1.5 months to 18 months.
There are no universally agreed upon "functional ability" outcomes. For
this reason, it was very difficult to review and compare the literature. The
Subcommittee therefore deliberately decided to be liberal in selecting the
criteria of outcomes related to functional ability. The outcomes reported in
the reviewed trials included, among others, gait speed, timed walking tests,
functional reach, and "get up and go," as well as performance on observational
functional health instruments such as the Short Physical Performance Battery
(SPPB), Physical Performance Test (PPT), McArthur Battery Scores, and
functional obstacle course. The subcommittee also reviewed trials that recorded
self-reported functional health using instruments such as the Functional Status
Questionnaire and the SF-36 (the emotional health SF-36 subscale was not
reviewed). ADLs and IADLs were measured using a variety of standardized
questionnaires. All of the trials demonstrated an improvement in one or more
functional ability outcomes. A reasonable question is whether the magnitude of
change seen in these trials on functional ability can affect role limitations
or ability. Most trials were underpowered to examine this question and did not
measure ADLs or IADLs.
The most recent, and one of the largest trials to date to address
physical activity and functional ability, is the Lifestyle Interventions and
Independence for Elders Pilot (LIFE-P) trial (62). LIFE-P
examined the effects of a mixed-modal physical activity intervention on
functional performance. The trial included 424 men and women aged 70 to 89
years who had mild to moderate functional limitations at baseline. The
participants were randomized to either a multi-modal exercise group or an
attention-matched control group. The people in the exercise group participated
in a combination of aerobic, strength, balance, and flexibility exercises (with
primary emphasis on walking). The muscle strengthening and flexibility
exercises focused on lower body extremity exercises. Subjects spent the first 8
weeks (adoption) attending 3 supervised center-based sessions per week. The
sessions lasted 40 to 60 minutes each. During the next 4 months (transition),
the number of center-based sessions was reduced to 2 times per week, and
home-based endurance/strength/flexibility exercises were started (3 or more
times per week). The subsequent maintenance phase consisted of the home-based
intervention, with optional once to twice per week center-based sessions. The
primary goal was to walk 150 minutes per week at a moderate intensity. The
intervention also included a strong behavioral component, with the participants
receiving 10 group-based behavioral counseling sessions during the first 10
weeks. The average walking time during the maintenance phase was 138 minutes
per week; average frequency of moderate physical activity per week was 6.4
times per week at 6 months and 5.1 times per week at 12 months. The people in
the attention-control group participated in a health education program. In this
trial, adverse events were carefully monitored and each group had similar rates
of non-serious and serious adverse events. The LIFE-P trial found that,
compared to those in the health education program, the people who participated
in the exercise intervention were able to significantly improve both their SPPB
and 400-meter walking speed during the 1.2-year intervention
(P<0.001). This pilot study also showed a trend toward a reduction
in the risk of major mobility disability (i.e., inability to walk 400 meters)
(hazard ratio = 0.71, CI 0.44 to 1.20) although this pilot study was not
powered for this outcome. In another recent large study (n=486) in very old men
and women (85 years or older) in Finland, a multi-dimensional 17-month
intervention that included exercise (walking, group exercises, and/or home
exercises) demonstrated no improvements in ADLs. However, mobility score and
balance improved more in the intervention group than in controls (58).
The Women's Health and Aging Study (WHAS) was a longitudinal cohort
study that met the criteria for inclusion in this review (41). In this study, 1,002 women aged 65 years and older who
had functional limitations at baseline were recruited. Of the 800 functionally
limited women who could walk unassisted at baseline and were alive and
contacted 1 year later, 226 (28%) walked regularly at least 8 blocks per week.
These women exhibited better health and functioning than did non-walkers. In
addition, walkers were 1.8 times more likely (95% CI 1.2 to 2.7;
P=0.002) to maintain reported walking ability and showed less decline
in customary walking speed and functional performance score over the follow-up
period. A Finish cohort study of 1,109 men and women (aged 65 years or older)
were followed for 8 years (31). Subjects at baseline were
either functionally impaired or had no functional limitations and all subjects
(regardless of functional status) were categorized as being sedentary or
active. Among those who were impaired at baseline, those who were active had a
reduced risk of becoming dependent (role limitation) over the 8-year
follow-up.
Four relevant systematic review papers focused on different aspects of
functional health (64-67). The most recent review was that
of Baker and colleagues (64). The authors limited their
review to only randomized controlled exercise trials of at least 3 modalities
of training, e.g., strength, aerobic, and balance. The 3 modes of training had
to be conducted concurrently. Many interventions have focused on these 3 modes
of exercise in combination because older adults who are at risk of functional
limitations generally have deficits in these areas. Therefore, it makes sense
to target these areas with a multi-modal exercise program. In addition, the
review only considered trials with subjects aged 60 years or older. The authors
systematically reviewed 15 studies totaling 2,149 subjects. A low effect size
was seen for changes in dynamic strength (mean 0.41, range −0.08 to
1.67), and balance improved in only 6 of the 11 studies that included balance
as an outcome (the positive effect on reducing falls is reported in
Question 3). The authors concluded that the effect
size for functional health changes were minimal when all studies were
considered. The authors gave a number of reasons for the low effect size of
these multi-modal interventions on functional health. One reason was that a
ceiling effect may have prevented further improvement in some functional
measures, as many of the trials reviewed included subjects with high baseline
functional ability. However, the authors posited that the most likely reason
for a small effect size was that the intensity and duration of any given
modality was not robust enough to elicit meaningful physiologic changes that
could affect functional health. The authors of the review suggest that more
evidence is needed to establish whether multi-modal exercise at adequate
volumes and intensity is feasible and effective in older populations and
whether multi-modal interventions are in fact more effective than single mode
interventions. The LIFE-P study described above and the study of Binder and
colleagues (52) were exceptions to the findings in this
review, as these 2 studies did show better outcomes. This is most likely due to
the size of these studies, the functional limitations of the subjects at
baseline, robust interventions, objectively measured primary outcomes, and the
length of the trials.
Keysor and Jette reviewed 31 studies (28 RCTs and 2 quasi-experimental
trials) that examined the impact of various physical activity programs on
functional activities and/or disabilities among older adults (65). The mean age of subjects was older than age 60 years,
although the trials had no lower age limit for inclusion. Sample sizes of the
trials ranged from 24 to 439. The most consistent positive effects of exercise
were observed in strength, aerobic capacity, flexibility, walking, and balance,
with more than half of the trials that examined these outcomes finding positive
effects. Of the studies that examined physical, social, emotional, and overall
disability outcomes, most found no improvements. Only 5 of the studies in the
review reported reduced physical disability. The authors of the review note
that methodological issues may be one of the main limitations in the studies
that have examined disability outcomes. In another critical review by Keysor in
2003, the overall conclusions were similar (67). Exercise
increases muscular strength and aerobic capacity and improves functional
ability. However, it is less clear whether physical activity or exercise
prevents or minimizes disability.
The fourth review considered for Question 2 was that of Latham and
colleagues (66). In this review, the authors focused
solely on progressive resistance strength training interventions trials in
older adults (aged 60 years and older). The authors identified 62 trials with a
total of 3,674 subjects. The authors noted that most studies were of low
quality due to poor design, small numbers, unclear randomization schemes, and
other problems. Progressive resistance strength training showed a strong
positive effect on strength and the training had a modest effect on some
measures of functional limitations such as gait. No evidence of an effect was
found for physical disabilities in the 14 studies that reported disability
outcomes. It is important to note that the main objective of most of the trials
in the review was not to reduce disability. (Muscle strengthening activities
are addressed more fully in Part G.
Section 5: Musculoskeletal Health.)
Sex and Race/Ethnicity
Men and women have been represented about equally in the exercise trials
that were reviewed. Although not systematically tested, no evidence appears
that older men and women respond differently to exercise interventions focusing
on functional health. Many of the studies demonstrated that men had higher
physiologic and functional status than women at any given age. No trials
reviewed for this question had adequate numbers of non-whites to do
sub-analyses to determine whether responses to exercise differ among racial or
ethnic groups.
Comparison to Current Guidelines
Current recommendations from the American College of Sports Medicine
(ACSM) and the American Heart Association (AHA) recommend that older adults
participate in moderate to vigorous intensity aerobic activity, muscle
strengthening activity, and activities to maintain or increase flexibility;
balance exercises are recommended for older adults at risk of falls (68). Out
of the 12 randomized trials reviewed, 8 roughly met the recommendations
outlined by ACSM/AHA (52;54;56;57;59;61-63). The LIFE-P Trial and the studies by Binder and
colleagues and Nelson and colleagues saw robust improvements in functional
ability. The study of Binder and colleagues also saw an improvement in aerobic
capacity (VO2max). The effects of the interventions on functional
ability were not as robust in the studies of Cress and colleagues and King and
colleagues. This is most likely due to the fact that the subjects in these two
trials had higher functional ability at baseline, as both studies recruited
older subjects with and without functional limitations at baseline. It is
important to note that muscle strength and aerobic capacity (VO2max)
improved in the study of Cress and colleagues demonstrating an improvement in
physiologic capacity that was accompanied by modest improvements in functional
ability. Also of note, the study of King and colleagues used "flexibility"
exercises as their attention-control group (57). The subjects in this group had
greater reductions in self-reported bodily pain. This is one of the only
studies to investigate flexibility exercises.
Limited evidence suggests that functional health in older adults can be
improved with less frequent physical activity than recommended by the ACSM, as
the other 4 trials reviewed used interventions below this threshold and each
demonstrated some improvements in function ability (53;55;58;60).
Question 3: In Older Adults Who Are at
Increased Risk, Does Regular Physical Activity Reduce Rates of Falls and
Fall-Related Injuries?
Conclusions
Clear evidence demonstrates that participation in physical activity
programs is safe and can effectively reduce falls in older adults at elevated
risk of falls. Limited evidence indicates that physical activity programs
reduce injurious falls in older adults. Currently, the evidence is strongest
for physical activity interventions that include muscle strengthening and
balance training activities in combination with aerobic activities, especially
walking. In addition, moderate, but inconsistent, evidence shows that tai chi
exercise or balance-only training programs provide benefit.
Most of the interventions reviewed included a pattern of physical
activity that involves 3 times per week of balance and moderate intensity
muscle-strengthening at 30 minutes per session, with additional encouragement
to participate in moderate-intensity walking activities 2 or more days per week
for 30 minutes a session. It was difficult to ascertain an optimal dose for tai
chi, as risk reduction was seen in one trial with as little as 1 hour per week,
whereas other trials had greater frequency (e.g., 3 days per week). Limited
evidence suggests that physical activity levels less than those described above
provides some benefit.
Introduction
It is not until age-related decline in muscle strength and stability
reaches a critical threshold that the risk of falls and functional decline
threaten independent living. This threshold occurs when the daily activities of
life are at or near the limit of a person's physiologic capacity (e.g., muscle
strength and balance). Minor perturbations may precipitate the fall, but it
appears from epidemiologic studies that the underlying cause is the person's
critically compromised physical fitness particularly strength and
balance (69). Theoretically therefore, only small
improvements in strength and balance may be needed to lift the person above the
threshold where daily living activities are hazardous.
Numerous RCTs of interventions to prevent falls have been conducted in
older adults. A multi-component approach is now recommended to address factors
that increase fall risk (69), and so trials now commonly
test multi-component interventions. These components include removal of
environmental hazards (e.g., loose mats), medical treatment (e.g., eliminating
drugs that increase fall risk), and physical activity. However, it is difficult
to deduce post hoc which elements of a multi-component intervention
are efficacious, so the literature on multi-component interventions was not
reviewed.
However, some RCTs have focused on physical activity as the sole
intervention to prevent falls and fall injuries. As discussed below, these
trials typically test a multi-modal exercise intervention involving some
combination of aerobic (e.g., walking), muscle-strengthening, balance, and
flexibility activities, or they have tested tai chi.
Rationale
Using the Physical Activity Guidelines for Americans Scientific
Database and consultant suggestions, the subcommittee identified 8 systematic
reviews or meta-analyses addressing physical activity and falls (70-77). When necessary, the subcommittee reviewed the
original research papers referred to in the meta-analyses and reviews to
ascertain study details regarding subject population and physical activity
interventions.
The meta-analysis by Campbell and Robertson is the most recent analysis
that addresses physical activity and falls (70). The
authors employed stringent inclusion criteria for the analysis: 1) all studies
were RCTs; 2) all participants were aged 60 years or older or had a mean age
older than 70 years; 3) the majority of the participants lived independently in
the community; 4) fall events were recorded prospectively; 5) follow up lasted
at least 6 months; 6) at least 70% of the participants completed the trial; 7)
all falls during the trial for at least 50% of the participants were included
in the analysis; and 8) a relative rate ratio with 95% CI comparing the number
of falls in the intervention group and the control group were recorded. Twelve
physical activity trials met the inclusion criteria for the analysis (one of
the trials compared 2 different exercise interventions to controls (78). The pooled rate ratio was 0.71 (95% CI 0.61 to 0.82;
P<0.001), indicating that physical activity reduces risk of falls
(see Figure G6.3 and
Table G6.A3) The trials included
strength and balance training (79-85), computerized
balance training (78), tai chi (78;86-88). One study included endurance training and/or strength
training (89).
Pooled rate ratio 0.71 (95% CI 0.61 to 0.82;
P<0.001). Tests for heterogeneity Q = 21.49, P=0.044; I2 =
44%.
Source: Adapted with permission from Age and Ageing
2007;36 pp.656-62, Figure 2b. "Rethinking individual and community fall
prevention strategies: a meta-regression comparing single and multifactorial
interventions." Campbell A and Robertson M.
Figure G6.3. Data Points
Trial |
Rate Ratio* |
95% CI Lower Limit |
95% CI Upper Limit |
SE |
Wolf et al., 1996 (a) (78) |
0.525 |
0.321 |
0.86 |
0.138 |
Wolf et al., 1996 (b) (78) |
1.14 |
0.733 |
1.76 |
0.262 |
Buchner et al., 1997 (89) |
0.61 |
0.39 |
0.93 |
0.138 |
Campbell et al., 1997 (81) |
0.68 |
0.52 |
0.90 |
0.097 |
Campbell et al., 1999 (b) (80) |
0.87 |
0.36 |
2.09 |
0.441 |
Robertson et al., 2001 (84) |
0.54 |
0.32 |
0.90 |
0.148 |
Barnett et al., 2003 (79) |
0.60 |
0.36 |
0.99 |
0.161 |
Lord et al., 2003 (83) |
0.78 |
0.62 |
0.99 |
0.094 |
Wolf et al., 2003 (88) |
0.75 |
0.52 |
1.08 |
0.143 |
Campbell et al., 2005 (b) (82) |
1.15 |
0.82 |
1.61 |
0.202 |
Li et al., 2005 (86) |
0.45 |
0.30 |
0.70 |
0.102 |
Skelton et al., 2005 (85) |
0.69 |
0.5 |
0.96 |
0.117 |
Voukelatos et al., 2007 (87) |
0.65 |
0.47 |
0.89 |
0.107 |
Most of these trials and others were reviewed in a second systematic
review by the same authors (90). The total number of
participants in the 27 trials reviewed was 5,169. Four trials included women
only and one study included only men. The majority of the studies involved
independent older adults. One study included older adults living in retirement
communities. A significant reduction in the number of all falls during the
study was demonstrated in 6 of the 9 studies that included analysis of multiple
falls. The reduction in the number of falls between intervention and controls
ranged from 22% to 47.5%.
It should be noted that numerous trials have not shown a reduction in
falls. Many fall prevention trials have been insufficiently powered. Numerous
studies include too few subjects, have inadequate length of follow up or
include subjects who are not at risk for falls. For this reason, many trials
have not been successful at demonstrating an effect of physical activity on
reducing falls (72;90).
Most of the interventions trials that have demonstrated a reduction in
falls have included several exercise modalities: strength, balance training,
exercises based on functional activities (e.g., chair stands, reaching, stair
climbing), coordination activities (e.g., dance, ball games), walking outside
or other endurance activities, and progression in the difficulty and complexity
of the program. Currently, interventions with the most evidence include
strength and balance training to reduce falls. One meta-analysis pooled and
analyzed 4 trials that used a similar exercise intervention (the Otago Exercise
Programme from New Zealand, which focuses on home-based strength and balance
training) (76). The meta-analysis included 1,016 community
dwelling women and men aged 65 to 97 years. The results from this study
demonstrate a reduction in falls of 35% (95% CI 0.57 to 0.75). In addition,
this analysis demonstrated a 35% reduction in the number of injurious falls
(95% CI 0.53 to 0.81). Subjects aged 80 years and older benefited significantly
more than did subjects aged 65 to 79 years of age.
Evidence also exists that tai chi exercise training programs provide
benefit (75;77;86;87), although the evidence is
inconsistent (77). Tai chi exercises consist of slow but
continuous movements of all parts of the body incorporating elements of
strength, balance, coordination, postural alignment, and concentration (77).
All of these areas of fitness are related to risk of falls. To date, several
studies examining tai chi have shown a reduction in falls in older adults (78;86;87). The
reason for the success of these trials may be due to their study design in
terms of size (all studies had more than 200 subjects) and duration (all
studies lasted for 1 year or longer).
Pattern of Exercise
The frequency and duration of the exercise programs in the successful
exercise trials vary. In the 9 positive exercise interventions (out of 13)
analyzed in the recent meta-analysis by Campbell and Robertson (70), frequencies included 1 hour per week of center-based
strength, balance, endurance and coordination instruction with home exercises
encouraged (79), 1 hour 2 times per week of center-based
strength, balance, endurance, and coordination instruction (83), 1 hour 3 times per week of center-based strength and/or
aerobic training (89), 30 minutes 3 times per week of
home-based strength and balance with additional encouragement to walk for 30
minutes 2 or more times per week (81;84), 1 hour per week to 1 hour 3 times per week of tai chi
(86), 45 minutes 2 times per week of center-based tai chi
with daily home exercises encouraged (78), center-based
strength, balance, flexibility and endurance program for 36 weeks for 1 hour a
week, and the home-based Otago Exercise Programme 2 times a week for 30 minutes
(85).
The falls prevention program from New Zealand the Otago Exercise
Programme merits description, as it has been studied the most. The
details of this program are outlined in an instructional review paper (91). Briefly, through several home visits, a trained
instructor teaches an individualized, progressive, moderate-intensity lower
body muscle strengthening exercises using ankle cuff weights in addition to
balance exercises. Balance exercises progress from holding on to a stable
support, such as furniture, to performing exercises independent of support.
Exercises include: knee bends, backward walking, sideways walking, tandem
stance and walk, heel walking, toe walking, and sit-to-stand. The participant
is instructed to perform these activities 30 minutes 3 times per week and is
also encouraged to walk outside for at least 30 minutes 2 or more times per
week.
A few caveats of these results should be noted. First, the benefits
continue as long as the programs are carried out (80) but
there is no reason to believe that benefits would persist once the programs are
stopped. In addition, the activities must be specifically designed for fall
prevention. Less-specific exercise programs, such as brisk walking do not
reduce falls. In fact, one program of brisk walking increased the fall rate (92). Also, high-intensity training in a frail population may
increase musculoskeletal symptoms without decreasing falls (66). The intensity of most of the successful interventions
would be considered moderate. Lower-intensity interventions do not seem to be
of much value (93-95).
Sex, Age, and Race/Ethnicity
Far more women than men have participated in research studies on falls
(69). However, it appears that men and women benefit
equally from physical activity falls prevention programs (63;76). Although the sex of participants
may not have a significant impact on success of intervention trials, age does.
Exercise programs are most successful when they include subjects aged 80 years
and older and/or include subjects who have a history of falling (70). This is most likely due to baseline impaired strength
and balance arising from low levels of physical activity that underlie many
falls experienced by elderly people, especially those aged 80 years and older.
Currently, no data are available to ascertain whether response to physical
activity and falls prevention differs by race or ethnicity.
Comparison to Current Guidelines
Current recommendations from the ACSM and the AHA include balance
training for older adults at risk of falls as well as aerobic and strength
training (68). In addition, guidelines for the prevention
of falls from the American Geriatric Society also recommend physical activity,
especially with balance training as one of the components (69). It should be noted that neither the ACSM/AHA nor the AGS
guidelines provide recommendations for the frequency or duration of balance
training.
The Otago Exercise Programme used in 4 intervention trials meets the
ACSM/AHA recommendations, and this program has been shown to be successful at
reducing falls in older community-dwelling people (76).
Evidence also suggests that programs meeting just less than the ACSM/AHA
recommendations (e.g., frequency of less than 5 days per week) also are
successful at reducing falls (79;83;85). However, all of these programs
still combine muscle strengthening and balance exercises in addition to
walking. The results from the studies that focused on tai chi are more
difficult to compare to the ACSM/AHA recommendations due to the nature of the
activity, but clearly, balance is an important element of tai chi and several
of the tai chi trials showed a reduction in falls (75;77;86;87).
Overall Summary and Conclusions
Regular physical activity has substantial health benefits. It is
important to characterize the benefits in terms of preventing diseases and
premature mortality, which is the purpose of most chapters of this report. It
is also important to characterize the benefits in terms of the impact of
physical activity on ability to perform the tasks of everyday life, which is
the overarching purpose of this chapter. The Functional Health subcommittee
focused on 3 questions pertaining to middle aged and older adults: (1)
Does physical activity prevent or delay the onset of functional limitations
and/or role limitations? (2) In adults with existing functional limitations
and/or role limitations, does physical activity have a beneficial effect on
functional ability and role ability? (3) Does physical activity reduce risk of
falls and injurious falls?
Scientific evidence pertaining to each of these questions was
systematically sought and reviewed. Based upon this evidence, the
subcommittee's main conclusions are:
- Strong, consistent observational evidence indicates that mid-life
and older adults who participate in regular physical activity have reduced risk
of moderate or severe functional limitations and role limitations. Active
mid-life and older individuals both men and women have
approximately a 30% lower risk of developing moderate or severe functional
limitations or role limitations compared with inactive individuals. The
evidence of benefit is strong for aerobic activity, but limited for other types
of activity (muscle-strengthening, balance, and flexibility activities).
- In older adults with existing functional limitations, moderate,
fairly consistent evidence indicates that regular physical activity is safe and
has a beneficial effect on functional ability. The evidence of benefit is
moderate for physical activity involving both aerobic and muscle strengthening
activities, but evidence is limited for any single type of activity used alone.
Further, evidence to conclude that physical activity improves or maintains role
ability is currently limited.
- In older adults at risk for falls, evidence is strong that regular
physical activity is safe and reduces falls. The evidence of benefit is strong
for physical activity programs that emphasize both balance training and
muscle-strengthening activity, and also include some aerobic activity,
especially walking. Moderate evidence also indicates that tai chi exercise
programs provide benefit, although the data are inconsistent. In older adults
without substantial functional limitations and at low risk of falls, limited
evidence indicates that physical activity reduces fall risk. Further, limited
evidence suggests that physical activity reduces risk of injurious falls (e.g.,
fractures) in older adults.
In addition, previous reviews of scientific evidence have established
that physical activity in middle-aged and older adults improves physical
fitness and physiologic capacity (aerobic, strength, and balance) even into
advanced age (3;96).
In summary, physical activity can help prevent or delay the onset of
functional and/or role limitations, improve functional ability, and reduce
falls. Because older adults have the lowest physical activity participation
rates of any age group and have the highest risk of disability, increasing
physical activity in older adults is an important public health goal.
Research Needs
It is important that future research on older adults and physical
activity develop a consensus around standardized and meaningful outcomes for
assessing functional health and disability. Developing universally agreed-upon
outcome measures in this area will greatly assist future evaluations of
research. The research to date demonstrates that moderate-intensity,
multi-modal interventions appear to have benefit. However, it is not known
whether: 1) single-mode interventions (e.g., walking alone) are equally
effective; 2) a threshold or dose effect of physical activity exists that
affects functional health; 3) higher intensity interventions are more or less
effective than moderate-intensity activity and 4) these interventions are
equally effective in understudied populations.
The impact of power training on improving functional ability in older
adults has been addressed in a few trials and shows promise (60;97) and is addressed in greater
detail in Part G. Section 5:
Musculoskeletal Health. Future research should address more
fully whether power training is effective, feasible, and safe for older adults
with functional limitations. Most importantly, due to the high economic costs
associated with disability, future research needs to focus on large-scale
well-designed trials to ascertain whether physical activity programs can
prevent disability and role limitations as people advance into old age.
With respect to falls, although existing research provides strong
evidence that physical activity programs decrease fall risk, it is still not
clear which programs are most suitable for which population groups. For
example, is tai chi better for a younger population and an individualized
home-based program more suitable for those who are older? Similar to
Question 2, it appears that moderate intensity
multi-modal interventions appear to have benefit. However, we do not know
whether there is a threshold or dose effect of physical activity on reducing
falls or whether higher-intensity interventions are more or less effective. We
also do not know whether interventions are equally effective in across all
population groups. To date, only a few research studies have addressed whether
injurious falls are reduced with physical activity programs in older adults (80). Although fractures are discussed in detail in
Part G. Section 5: Musculoskeletal
Health, it deserves mentioning here that an RCT with
sufficient power is needed to assess whether physical activity can reduce
fractures as an endpoint. This is an important research topic because 90% of
hip fractures result from falls.
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