NHEFS Survey description The NHANES I Epidemiologic Followup 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 followup 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 followup 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 followup. Tracing rates for each completed wave ranged from 90 to 94 percent and interview rates ranged from 91 to 96 percent of those traced. Table 1. Available NHEFS Data +----------------------+---------+---------------------------------------------- | Dataset Name |Release |Size in |Data Files / Description | |Date |Megabytes| +----------------------+---------+---------+--------------------------------------------+ |NHEFS, 1982-84, |December | 10.6 |The 1982-84 Interview Data tape contains |Interview Public Use |1987 | |information collected from the subject and |Data Tape | | |proxy interviews conducted during the 1982-84 |Documentation | | |followup period. When merged together, the | | | |NHEFS Interview data files provide a complete |NHEFS, 1982-84, | | |followup history for each subject from |Interview Public Use |December | 50.7 |baseline through the last completed interview. |Date Tape |1987 | | +----------------------+---------+---------+--------------------------------------------+ |NHEFS, 1982-84, |November | 2.72 |The revised 1982-1984 Health Care Facility |Revised Health Care |1990 | |Stay tape contains information collected |Facility Stay Public | | |during the 1982-84 followup period regarding |Use Data Tape | | |overnight stays in health care facilities, |Documentation | | |including diagnostic and summary information | | | |abstracted from hospital and nursing home |NHEFS, 1982-84, |November | 10.4 |records. |Revised Health Care |1990 | | |Facility Stay Public | | | |Use Data Tape | | | |+---------------------|---------|---------|--------------------------------------------+ |NHEFS, 1986, |April | 2.80 |The 1986 Health Care Facility Stay tape |Health Care Facitlity |1990 | |contains information collected during the 1986 |Stay Public Use Data | | |followup period regarding overnight stays in |Tape Documentation | | |health care facilities, including diagnostic | | | |and summary information abstracted from |NHEFS, 1986, |April | 2.22 |hospital and nursing home records. |Health Care Facility |1990 | | |Stay Pulic Use Data | | | |Tape | | | |+---------------------+---------+---------+---------------------------------------------+ |NHEFS, 1986, |April | 8.39 |The 1986 Interview Data tape contains |Interview Public Use |1990 | |information collected from the subject and |Data Tape | | |proxy interviews conducted during the 1986 |Documentation | | |followup period. When merged together, the | | | |NHEFS Interview data files provide a complete |NHEFS, 1986, |April | 18.4 |followup history for each subject from |Interview Public Use |1990 | |baseline through the last completed interview. |Data Tape | | | +----------------------+---------+---------+----------------------------------------------+ |NHEFS, 1987, |October | 2.56 |The 1987 Health Care Facility stay tape |Health Care Facility |1991 | |contains information collected during the 1987 |Staty Public Use Data | | |followup period regarding overnight stays in |Tape Documentation | | |health care facilities, including diagnostic | | | |and summary information abstracted from |NHEFS, 1987, |October | 3.02 |hospital and nursing home records. |Health Care Facility |1991 | | |Stay Public Use Data | | | |Tape | | | |----------------------|---------|---------|---------------------------------------------+ |NHEFS, 1987, |October | 8.92 |The 1987 Interview Data Tape contains |Interview Public Data |1991 | |information collected from the subject and |Tape Documentation | | |proxy interviews conducted during the 1987 | | | |followup period. When merged together, the |NHEFS, 1987, |October | 49.5 |NHEFS Interview data files provide a complete |Interview Public Data |1991 | |followup history for each subject from |Tape | | |baseline through the last completed interview. +----------------------+---------+---------+---------------------------------------------+ |NHEFS, 1992, |July | 2.86 |The 1992 Health Care Facility stay tape |Health Care Facility |1996 | |contains information collected during the 1992 |Stay Public Use | | |followup period regarding overnight stays in |Documentation | | |health care facilities, including diagnostic | | | |and summary information abstracted from |NHEFS, 1992, |July | 4.33 |hospital and nursing home records. |Health Care Facility |1996 | | |Stay Public Use Data | | | |Tape | | | +----------------------+---------+---------+---------------------------------------------+ |NHEFS, 1992, |July | 16.5 |The 1992 Interview Data Tape contains |Interview Public Use |1996 | |information collected from the subject and |Tape Documentation | | |proxy interviews conducted during the 1992 | | | |followup period. When merged together, the |NHEFS, 1992, |July | 71.5 |NHEFS Interview data files provide a complete |Interview Public Use |1996 | |followup history for each subject from |Data Tape | | |baseline through the last completed interview. +----------------------+---------+---------+---------------------------------------------+ |NHEFS, 1992, |July | 3.19 |The 1992 Mortality Data tape contains death |Mortality Public Use |1996 | |certificate information collected during each |Data Tape | | |followup period coded according to ICD-9 |Documentation | | |multiple-cause-of-death procedures for all | | | |4,497 decedents identified through 1992. |NHEFS, 1992, |July | 1.89 | |Mortality Public Use |1996 | | |Data Tape | | | +----------------------+---------+---------+---------------------------------------------+ |NHEFS, 1992, |July | 3.24 |The 1992 Vital and Tracing Status tape contains |Vital and Tracing |1996 | |tracing, vital status, and demographic data |Status Public Use Data| | |for all 14,407 subjects for each wave of data |Tape Documentation | | |collection. | | | | |NHEFS, 1992, |July | 3.76 | |Vital and Tracing |1996 | | |Status Public Use Data| | | |Tape | | | -----------------------+---------+---------+---------------------------------------------+ |NHEFS, Health Care |July | 2.33 |The Supplemental Health Care Facility stay |Facility Stay |1996 | |data tape has been created to provide |Supplement Public Use | | |information on overnight facility stays that |Data Tape | | |occurred outside the reported followup |Documentation | | |period. | | | | |NHEFS, Health Care |July | 29.4 KB | |Facility Stay |1996 | | |Supplement Public Use | | | |Data Tape | | | +----------------------+---------+---------+---------------------------------------------+ Data file description The 1992 NHEFS Vital and Tracing Status Public Use Data Tape contains vital status, tracing and demographic information on all examined subjects 25 years or older at NHANES I (n=14,407). It also provides users with information on the availability of different survey components for each of the four followup periods for each subject. The 1992 Mortality Data tape contains death certificate information collected for each followup period (1982-84, 1986, 1987, and 1992) coded according to ICD-9 multiple-cause-of-death procedures for all 4,497 NHEFS decedents identified through 1992. A survey period identifier variable is provided to allow the researcher to select mortality information for each of the four followup periods. The Interview data tapes contain information collected from the subject and proxy interviews conducted during each NHEFS data collection period. When merged together, these files provide a complete followup health history for each subject from baseline through the last completed interview. The Health Care Facility Stay tapes contain information collected regarding overnight stays in health care facilities reported during each NHEFS survey period. The Supplemental Health Care Facility Stay data tape has been created to provide information received during the 1992 followup period but which describes overnight facility stays that occurred prior to the 1992 followup period. When all five Health Care Facility Stay data files are merged together, they provide a history of all reported hospitalizations and institutionalizations from baseline through 1992. Data from the NHEFS public use data tapes should be linked to the NHANES I public use data files for the proper analysis of longitudinal data. Data users are directed to consult the Vital and Statistics Series 1 Reports Nos. 22, 25, 27 and 35 for information regarding the plan and operation of the NHEFS surveys. A Vital and Health Statistics Series 2, Report No. 121 has been issued to assist data users with resolving statistical issues and the proper use of sample weights when analyzing the NHEFS data. The data collected in the NHEFS surveys is longitudinal by design and therefore should, in most cases, not be used to provide prevalence estimates. Guidelines for Citation of NHEFS Data With the goal of mutual benefit, the National Center for Health Statistics(NCHS) requests that recipients of data files cooperate in certain actions related to their use. Any published material derived from the data should acknowledge NCHS as the original source. The suggested citation to appear at the bottom of all published tables is as follows: Source: National Center for Health Statistics (NHEFS) When cited in a bibliography, the citation should read: National Center for Health Statistics. Data File Documentation, NHANES I Epidemiologic Followup Study (NHEFS), (machine readable data file and Documentation) National Center for Health Statistics, Hyattsville, Maryland. The published material should also include a disclaimer that credits any analyses, interpretations, or conclusions reached to the author (recipient of the data file) and not to NCHS, which is responsible only for the initial data. Consumers who wish to publish a technical description of the data should make an effort to insure that the description is not inconsistent with that published by NCHS. Problems Using the Data NHEFS is a rich source of data and NCHS encourages you to use the data for research and analysis. However, the dataset is large and complex and familiarity with data file manipulation and analysis is required. NCHS does not have the resources to perform analyses, check results, debug programs or do literature review for your work. Thorough review of the extensive documentation on the planning of the survey, analytic guidelines and individual datasets should resolve most questions. If you still have questions after careful review of the documentation, please contact the Data Dissemination Branch at (301) 458-4636 or refer to the web page at http://www.cdc.gov/nchs.