|National Center for Health Statistics
Centers for Disease Control and Prevention
Department of Health and Human Services
The National Health and Nutrition Examination Survey (NHANES) obtains information about the health and nutritional status of a representative national sample of the civilian, non-institutionalized population of all ages through direct interviews, physical examinations which obtain a wide variety of standardized medical information, and selected laboratory analyses. Data collected through NHANES assist in understanding and evaluating new public health issues and technology; risk factors for specific diseases; the relationship between diet, nutrition, and health; trends in risk behaviors and environmental exposures; the prevalence, awareness, treatment, and control of selected diseases; the number and percent of persons in the population and specific subgroups with diseases and risk factors; and in establishing a national probability sample of genetic and other materials.
Examples of the subjects covered in NHANES included prenatal care, birthweight, preschool/child care, current medical conditions, reported pain, physical functioning, immunization status, presence of selected diseases (TB, diabetes, cardiovascular disease, osteoporosis, kidney conditions, respiratory health), blood pressure, vision, audiometry, balance, oral health, diet behavior and nutrition, weight history, smoking and tobacco use, and use of dietary supplements and prescriptions. The medical examination includes a diagnostic interview, body measurements, bone desistometry, a dental examination, vision, hearing, physical fitness, physical functioning, and selected laboratory tests. Extensive demographic and socio-economic information also is collected.
Currently (1999), each year a new sample of 5,000 individuals of all ages is interviewed and examined; results can be aggregated across years to improve reliability of the estimates.
The questions concerning race/ethnicity are consistent with the proposed OMB guidelines; that is, the item on Hispanic origin precedes the race question, and one or more categories may be selected. The specific questions are as follows:
- (Do you) consider (yourself) Hispanic/Latino?
Please give me the number of the group that represents (your) Hispanic original ancestry. Please select one or more categories. (Hand card) Puerto Rican Mexican/Mexicano Other Latin American (specify) Cuban/Cuban American Mexican-American Other Hispanic (specify) Dominican (Republic) Chicano What race (do you) consider (yourself) to be? Please 1 or more of these categories. White Guanmanian Filipino Black/African American Samoan Japanese Indian (American) Other PI (specify) Korean Alaska Native Asian Indian Vietnamese Native Hawaiian Chinese Other Asian (specify) Some other race (specify) (If more than 1 entry, continue) which one of these groups, that is (display responses) would you say best represents (your) race? Enter race code Cannot choose 1 race Refused
Given the large extent of oversampling of Mexican-Americans, NHANES both ensures the availability of Spanish-speaking interviewers and (as required) makes special efforts to conduct the interview in Spanish. The basic survey form also is available in Spanish. Consequently, about half of all Hispanic households are interviewed in Spanish. If an interviewer encounters a respondent who speaks neither English nor Spanish, a bilingual member of the family, if available, is enlisted as a translator. As needed, other language skills are provided. Most NHANES interviewers are bilingual.
Both NHANES III and current NHANES oversample Mexican-Americans and blacks in order to permit separate analyses of these two race/ethnic groups. NHANES III produced reasonably reliable statistics for a set of 52 age-sex-race/ethnicity groups; 14 for both Mexican-Americans and blacks, and 24 for whites and all other persons. The current NHANES will provide similar detail when several years of data collection are combined. In order to achieve these goals, approximately equal size samples in the 52 groups are required. Superimposed on this was an oversampling of Mexican-Americans in geographic areas containing high concentrations of Mexican-Americans. The combination of these two features of the sample resulted in sampling rates for Mexican-Americans varying in a range from 7.5 to 1. Asian and Pacific Islanders were sampled at the same rate as white persons and their sampling varied in a range of 20 to 1. The range among all age-sex-race/ethnicity groups was over 120 to 1. This diversity in sampling rates contributed significantly to the design effects for NHANES on statistics for all age-sex groups combined and the effective sample size is much lower than the nominal sample size, which was already very small for the API’s.
In spite of the diversity in sampling rates, the NHANES III sample sizes provide data with fairly good precision for Mexican-Americans in each of the 14 age-sex domains designated by NCHS for separate analysis. On the other hand, the sample size for even the total API population and for Native Americans is quite low, and it was trivial for individual age-sex groups. The current NHANES is expected to follow a similar pattern for combined years of data.
Publications of data for Hispanics, Asians, Pacific Islanders, and Native Americans
Given the relatively small overall sample size, separate data are not shown for any of the subgroups, other than for Mexican-Americans and Blacks. However, an examination of the feasibility of conducting studies on specific subpopulations in future surveys, to be called "Designated Population HANES," is currently underway. Public use micro-data files are released for each cycle with the race/Hispanic data grouped into categories for analytic purposes.
Revised race/ethnic definitions
As noted, the current NHANES utilizes the revised OMB standards for collecting race/ethnic data.