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NCHS Home | NHIS Home | Physical Activity Home | List of Topics | Questions | Guide | Recodes | References | CDC/NCHS Privacy Policy Notice | Accessibility | Search NCHS | Contact us |
Recodes
Adult Leisure-Time Physical Activity
In an effort to assist researchers interested in historical trends in leisure-time physical activity, the Adult Physical Activity website provides SAS code to generate leisure-time physical activity recodes for: (1) the Health Promotion and Disease Prevention/Year 2000 Objectives Supplements (1998, 1995, 1991, 1990, and 1985); and (2) the Sample Adult Core (1997 forward).
Supplements
The Health Promotion and Disease Prevention/Year 2000 Objectives Supplements each contained a series of questions asking frequency, duration, and intensity of more than 20 leisure-time sports, exercises, and physically active hobbies. Using this information and applying estimates of kilocalorie expenditures associated with each activity, two recodes are created: (1) KCAL --a estimate of average total kilocalories per kilogram of body weight per day over a recent two-week period, and (2) PA_LEVEL--- a categorical variable based on kilocalorie (kcal) expenditure: sedentary (kcal < 1.5), moderately active (1.5 < kcal < 3.0), and very active (kcal > 3.0).
The questionnaires for 1985 and 1990 were identical. Similarly, the questionnaires for 1991, 1995 and 1998 were identical. Caution should be used when studying trends that bridge the 1990 to 1991 questionnaire change. Age restrictions that were imposed for many of the leisure-time physical activities in the 1985 and 1990 questionnaires were removed beginning in 1991. Although the questions remained the same within these two time periods, valid value ranges and coding of “unknown” and “not asked” categories differed across the data years.
Description of the logic underlying the calculation of KCAL across all data years:
KCAL
= the sum of all mentioned activities for which both frequency and duration
have valid values. [If heart rate is missing, it is imputed to the lowest
value for purposes of calculating the recode.]
Kilocalorie
values for individual activities [KCALPI(I)] are calculated based on
frequency, duration, and heart rate intensity during the activity. The
individual KCALPI(I) values, rounded to one decimal, are then summed to
create the recode KCAL, the total average daily kilocalorie expenditure over
the two–week period. The values for individual activities [KCALPI(I)] are
stored in the data file and may be of methodological interest but are not in
themselves considered recodes.
If
an activity is mentioned but frequency or duration is missing and no other
activities are mentioned, then KCAL=99999.9.
If
all activities are “no,” then KCAL=00000.0.
If
some activities are “no” and others are unknown, then KCAL=99999.9
If
some or all activities were not asked (due to age or handicap), and the
respondent did not volunteer that he or she engaged in the activities, “not
asked” is treated as “no” for purposes of calculating KCAL. If the
respondent volunteered one or more activities, his or her KCAL value is
based on those volunteered activities.
A summary of the Energy Expenditures assigned in these recodes is provided.
SAS code for generating the KCAL AND PA_LEVEL recodes for each year:
NOTE: The recodes KCAL and PA_LEVEL exist on the 1998 NHIS Year 2000 Objectives public use data file. For consistency across data years, input variables for 1995, 1991, 1990, and 1985 have been renamed to be consistent with the 1998 naming conventions.]
Sample Adult Core
In 1997, questions about usual light-moderate and usual vigorous leisure time physical activity were added to the NHIS Sample Adult core questionnaire. Although question wording was slightly different during the first half of 1997, these questions have remained unchanged since July 1997. Estimates based on these questions are routinely published in “Early Release from the National Health Interview Survey,” “Health, United States,” and (beginning in 2007) “Summary Health Statistics for U.S. Adults.” SAS code to create the recode “ACTIVE,” used in these reports, is provided. The 1998 Sample Adult data are used as the example but the code can be applied to any full data year since 1998.
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Comparison of Supplement and Core Leisure-time Physical Activity Recodes In 1998, the core and supplement questions on leisure-time physical activity were both asked of the same adult respondents during the same interview. Using the recodes specified here, the Comparison of Two Sets of Adult Leisure-Time Physical Activity Questions: 1998 National Health Interview Survey compares the two sets of questions in terms of population prevalence (Table A) and in terms of their associations with selected health status indicators (Table B). |
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Physical Activity Information Homepage
National
Health Interview Survey (NHIS) |
This page last reviewed October 15, 2008
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