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 1982-1984 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 1982-1984 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.
The 1982-1984, 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 1982-1984, 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.
- 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 theNHANES I Epidemiologic Follow-up Survey (NHEFS) linked mortality file, which extends the mortality follow-up period through December 31, 2011 and brings the total number of NHEFS decedents to 9,035. 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 NCHSNational Death Index (NDI). Due to confidentiality requirements, the NHEFS linked mortality file is only accessible through the NCHSResearch Data Center (RDC).
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.
Public Use Data Files and Documentation
NHEFS Data Linkage