Survey description
The NHANES I Epidemiologic Follow-up Study (NHEFS) is a national
longitudinal study that was jointly initiated by the National Center for
Health Statistics and the National Institute on Aging in collaboration with
other agencies of the Public Health Service. The NHEFS was designed to
investigate the relationships between clinical, nutritional, and behavioral
factors assessed in the first National Health and Nutrition Examination
Survey NHANES
I and subsequent morbidity, mortality, and hospital utilization, as
well as changes in risk factors, functional limitation, and
institutionalization.
The
NHEFS cohort includes all persons 25-74 years of age who completed a medical
examination at NHANES I in 1971-75 (n = 14,407). It is comprised of a series
of follow-up studies, four of which have been conducted to date. The first
wave of data collection was conducted for all members of the NHEFS cohort
from 1982 through 1984. It included tracing the cohort; conducting personal
interviews with subjects or their proxies; measuring pulse rate, weight, and
blood pressure of surviving participants; collecting hospital and nursing
home records of overnight stays; and collecting death certificates of
decedents.
Continued follow-up of the NHEFS population was conducted in 1986, 1987, and
1992 using the same design and data collection procedures developed in the
1982-84 NHEFS, with the exception that a 30-minute computer-assisted
telephone interview was administered rather than a personal interview; and
no physical measurements were taken. The 1986 NHEFS was conducted for
members of the NHEFS cohort who were 55-74 years of age at their baseline
examination and not known to be deceased at the 1982-84 NHEFS (n = 3,980).
The 1987 NHEFS was conducted for the entire nondeceased NHEFS cohort (n =
11,750). The fourth wave of data collection, the 1992 NHEFS, includes the
entire nondeceased NHEFS cohort (n = 11,195). Tracing and data-collection
rates in the NHEFS have been very high. Ninety-six percent of the study
population has been successfully traced at some point through the 1992
follow-up. Tracing rates for each completed wave ranged from 90 to 94
percent and interview rates ranged from 91 to 96 percent of those traced.
Data file description
The NHEFS public use data files are divided into four components. These are:
Vital
and Tracing Status Data
The 1992 Vital and Tracing Status contains tracing, vital status, and
demographic data for all 14,407 subjects for each wave of data collection.
Interview
Data
The 1982-84, 1986, 1987, and 1992 Interview data contain information
collected from the subject and proxy interviews conducted during each
follow-up period. When merged together, these files provide a complete
follow-up history for each subject from baseline through the last completed
interview.
Health
Care Facility Stay Data
The 1982-84, 1986, 1987, and 1992 Health Care Facility Stay data contain
information collected during each follow-up period regarding overnight stays
in health care facilities, including diagnostic and summary information
abstracted from hospital and nursing home records. Supplemental Health Care
Facility Stay data is used to provide information on overnight facility
stays that occurred outside the reported follow-up period. When these five
Health Care Facility Stay data files are merged together, they provide a
history of all reported hospitalizations and institutionalizations from
baseline through 1992.
Mortality
Data
The 1992 Mortality Data contains death certificate information collected
during each follow-up period coded according to ICD-9
multiple-cause-of-death procedures for all 4,497 decedents identified
through 1992.
Additional mortality data can be found on the
NHANES I Epidemiologic Follow-up Survey (NHEFS) linked mortality file,
which extends the mortality follow-up period through December 31, 2000 and
brings the total number of NHEFS decedents to 6,656. The NHEFS linked
mortality file includes death information for all those previously
identified as deceased during the NHANES I Epidemiologic Follow-up survey
periods, as well as, deaths identified through a probabilistic match with
the NCHS National Death Index (NDI).
Due to confidentiality requirements, the NHEFS linked mortality file is only
accessible through the NCHS Research Data
Center (RDC).
Geographic coverage
In the first National Health and Nutrition Examination Survey (NHANES I),
data were collected from a national probability sample of the civilian
non-institutionalized population. The NHANES I Epidemiologic Follow-up Study
attempts to trace and interview all study subjects at their current
location.
