History of NHANES

The current NHANES was born out of The National Health Survey Act of 1956. This particular piece of legislation provided for the establishment of a continuing National Health Survey to obtain information about the health status of individuals residing in the United States, including the services received for or because of health conditions. The responsibility for survey development and data collection was placed upon the National Center for Health Statistics (NCHS), a research-oriented statistical organization housed within the Health Services and Mental Health Administration (HSMHA) of the Department of Health, Education, and Welfare (now the Department of Health and Human Services). Since its inception in 1959, eight separate Health Examination Surveys have been conducted and over 130,000 people have served as survey participants.

The first three National Health Surveys—National Health Examination Survey (NHES) I, II, and III—were conducted between 1959 and 1970, each with an approximate sample size of 7,500 individuals. NHES I (1959-1962) focused on selected chronic diseases of adults between 18 and 79 years of age, while NHES II (1963-1965) and NHES III (1966-1970) focused on the growth and development of children (6-11 years of age) and adolescents (12-17 years of age), respectively.

Between the passage of the 1956 Act and the completion of NHES III, numerous nutrition-related studies were conducted that indicated that malnutrition remained a significant problem within certain segments of the U.S. population. This data, along with increasing scientific evidence linking dietary habits and risk for disease, prompted the Department of Health, Education, and Welfare to establish a continuing National Nutrition Surveillance System in 1969 (under the authority of the 1956 act) for the purposes of measuring the nutritional status of the U.S. population and monitoring the changes over time. Rather than conduct two separate surveys, which would require two separate samples and numerous additional hours of work, it was decided that the National Nutrition Surveillance System would be combined with the National Health Examination Survey, thereby forming the National Health and Nutrition Examination Survey, or NHANES.

Five NHANES have been conducted since 1970. NHANES I, the first cycle of the NHANES studies, was conducted between 1971 and 1975 and included a national sample of approximately 30,000 individuals between one and seventy-four years of age. Extensive dietary intake and nutritional status were collected by interview, physical examination, and a battery of clinical tests and measurements. NHANES II (1976-1980) included just slightly over 25,000 participants and expanded the age of the first NHANES sample somewhat by including individuals as young as 6 months of age. In addition, children and adults living at or below the poverty level were sampled at higher rates than their proportions in the general population ("oversampled") because these individuals were thought to be at particular nutritional risk.

While NHANES I and II provided extensive data regarding the health and nutritional status of the general U.S. population, it was somewhat biased against other ethnic groups residing in the United States, particularly Hispanics, whose numbers had been steadily increasing since data collection began in the 1960s. Thus, a Health and Nutrition Surveillance Survey specifically targeting the three largest Hispanic subgroups in the United States—Mexican Americans, Cuban Americans, and Puerto Ricans—was conducted between 1982 and 1984. The Hispanic Health and Nutrition Examination Survey (HHANES) was similar in design (i.e., similar instrumentation and data collection procedures) to the first two cycles of NHANES and included 16,000 individuals residing in regions across the United States with large Hispanic populations.

NHANES III (1988-1994) included a total of 40,000 individuals and expanded the age range even further than previous NHANES by including infants as young as two months of age, with no upper age limit on adults. In addition, to ensure the representativeness of both ethnicity and age, African Americans, Mexican Americans, infants, children, and those over sixty years old were oversampled. NHANES III also placed a greater emphasis on the effects of environment on health than either of the two previous NHANES (I and II). For example, data were gathered examining the levels of pesticide exposure, and the presence of carbon monoxide and various "trace elements" in the blood.

Beginning in 1999, NHANES became a "continuous survey." That is, unlike the previous NHANES surveys, which were conducted over a period of approximately four years with a "break" of at least one year between survey periods, the 1999-2000 survey was (and all subsequent surveys will be)

malnutrition: chronic lack of sufficient nutrients to maintain health environment: surroundings trace: very small amount

NHANES TIMELINE

National Health Examination Survey III (NHES III) 1966-1970

National Health Examination Survey I (NHES I) 1960-1962

National Health and Nutrition Examination Survey II (NHANES II) 1976-1980

National Health Examination Survey III (NHES III) 1966-1970

National Health Examination Survey I (NHES I) 1960-1962

National Health and Nutrition Examination Survey II (NHANES II) 1976-1980

National Health and Nutrition Examination Survey III (NHANES III) 1988-1994 a r ^

National Health Examination Survey II (NHES III) 1963-1965

National Health and Nutrition Examination Survey I (NHANES I) 1971-1975

Hispanic Health and Nutrition Examination Survey (HHANES) 1982-1984

National Health and Nutrition Examination Survey III (NHANES III) 1988-1994 a r ^

National Health Examination Survey II (NHES III) 1963-1965

National Health and Nutrition Examination Survey I (NHANES I) 1971-1975

Hispanic Health and Nutrition Examination Survey (HHANES) 1982-1984

National Health and Nutrition Examination Survey (NHANES 1999-2000) 1999-2000

conducted without breaks, on a yearly basis. As the survey period is shorter in length, the subject sample will be smaller. The 1999-2000 survey included nutritional and medical data on approximately 8,837 individuals up to 74 years of age.

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