About This Early Release

Early Release of Selected Estimates Based on Data From the January-June 2003 National Health Interview Survey

In this release, the National Center for Health Statistics (NCHS) updates estimates for 15 selected health measures based on data from the January-June 2003 National Health Interview Survey (NHIS), along with estimates from 1997 through 2002 for comparison. The 15 Early Release measures are being published prior to final data editing and final weighting to provide access to the most recent information from the NHIS. The estimates will be updated on a quarterly basis as a new quarter of the NHIS data become available.

The 15 measures included are lack of health insurance coverage and type of coverage, usual place to go for medical care, obtaining needed medical care, influenza vaccination, pneumococcal vaccination, obesity, leisure-time physical activity, current smoking, alcohol consumption, HIV testing, general health status, personal care needs, serious psychological distress, diagnosed diabetes, and asthma episodes.

For each selected health measure, a graph is presented showing the trend over time from 1997 through June 2003 for the total population, followed by graphs and tables showing estimates by age group and sex based on data from the January-June 2003 NHIS. Also, age- and/or sex-adjusted estimates are provided for three race/ethnic groups (Hispanic or Latino; not-Hispanic white, single race; and not-Hispanic black, single race) using data from the 2003 NHIS. Key findings are highlighted with bulleted text. Data tables providing values displayed in the graphs are included at the end of each section. This release also provides updates for age-adjusted estimates for Early Release measures that are also Healthy People 2010 leading health indicators (lack of health insurance coverage, usual place to go for medical care, influenza vaccination, pneumococcal vaccination, obesity, leisure-time physical activity, and current smoking)(1). The NHIS questions used to define the selected health measures are included in the appendix.

Race/ethnicity category

The race/ethnicity categories used are defined using the new (1997) standards for the classification of Federal data on race and ethnicity promulgated by the Office of Management and Budget (OMB)(2). Compared with the releases based on data through 2002, the categories "Not Hispanic white" and "Not Hispanic black" have been changed to "Not Hispanic white, single race" and "Not Hispanic black, single race." The terms "Hispanic" and "Black" have been changed to "Hispanic or Latino'' and "Black or African American,'' respectively. However, the text and graphs in this report use shorter terms for conciseness, and the tables use the complete labels. For example, the category "Not Hispanic or Latino, white, single race" in the tables is referred to as "Non-Hispanic white" in the text. Race/ethnicity-specific estimates for years prior to 2003 released previously were based on the 1977 OMB standards.

Data source

The data are derived from the three components of the 1997-2003 NHIS: the Family Core (collects information on all family members in each household), the Sample Adult Core (collects information from one randomly selected adult aged 18 years and over in a family), and the Sample Child Core (collects information on one randomly selected child in each family with a child in the NHIS). Data analyses for the January-June 2003 NHIS were based on 42,883 persons in the Family Core, 14,353 adults in the Sample Adult Core; and 5,762 children in the Sample Child Core. Visit the NHIS Web site for more information on the design, content, and use of the NHIS.

Transition to the 2000 census-based weights

Estimates were calculated by using the NHIS sample weights, which were calibrated to Census 2000 totals for sex, age, and race/ethnicity of the U.S. civilian noninstitutionalized population. In the previous reports released before September 2003, the weights for the 1997-2002 NHIS data were derived from 1990-based postcensal population estimates. Beginning with the 2003 data, the NHIS has transitioned to weights derived from the 2000 census-based population estimates. The impact of this transition was assessed for data from the 2000-02 NHIS by comparing estimates using the 1990 census-based weights with those using the 2000 census-based weights. The results are presented in tables I and II in the appendix. Although the changes for all selected measures are within one percentage point, the 2000-02 estimates for all selected measures have been recalculated using weights derived from the 2000 census. Information needed to revise the 1997-99 estimates based on intercensal estimates is not yet available.

Estimation procedure

NCHS creates weights for each calendar quarter of the NHIS sample. The NHIS data weighting procedure has been described in more detail elsewhere (Design and Estimation for the National Health Interview Survey, 1995–2004 [PDF - 300 KB]). Because the estimates for 2003 are being released prior to final data editing and final weighting, they should be considered preliminary and may differ slightly from estimates made later using the final data files. Except for health insurance coverage, estimates from the 1997-2002 NHIS were derived from the final data files for those years. However, as mentioned previously, estimates for 2000-02 were recalculated using the 2000 census-based weights that were not included in the final files. See "Health Insurance Coverage" section (section 1) in this release for details on special data editing for health insurance variables. For NHIS announcements and more detailed information, check the NHIS Web site .

Point estimates and estimates of their variances were calculated using the SUDAAN software package to account for the complex sample design of the NHIS. The Taylor series linearization method was chosen for variance estimation. All estimates shown meet the NCHS standard of having less than 30% relative standard error. Point estimates in some figures and tables are accompanied by 95% confidence intervals. Differences between percents or rates were evaluated using two-sided significance tests at the 0.05 level. Terms such as "greater than" and "less than" indicate a statistically significant difference. Terms such as "similar" and "no difference" indicate that the statistics being compared were not significantly different. Lack of comments regarding the difference between any two statistics does not necessarily suggest that the difference was tested and found to be not significant. Direct standardization was used to calculate age-sex-adjusted percents for three race/ethnic groups, using the year 2000 projected U.S. standard population(3). For the prevalence of obesity, only age-adjusted sex-specific percents are presented because the race/ethnic pattern in obesity prevalence differs by sex. Similarly, only sex-adjusted age-specific prevalences are presented for the asthma episodes measure because the race/ethnic patterns in asthma episodes differ by age. The age groups used for standardization varied depending upon the impact of age on the specific measure. Rates presented are crude rates unless otherwise stated.

Future plans for early release of NHIS estimates

The NCHS Early Release Program will update and release estimates 6 months after NHIS data collection has been completed for each quarter. These releases are tentatively scheduled for March, June, September, and December. New measures may be added as work continues and in response to changing data needs. Feedback on the Early Release mechanism and on the estimates is welcome (e-mail). Announcements about Early Releases, other new data releases, publications, or corrections related to the National Health Interview Survey (NHIS) will be sent to members of the HISUSERS Listserv. To join, visit the NCHS Listservs page.

Suggested Citation

Ni H, Coriaty-Nelson Z, Schiller J, Hao C, Cohen RA, Barnes P. Early release of selected estimates based on data from the January-June 2003 National Health Interview Survey. National Center for Health Statistics. /nchs/nhis.htm. December 2003.