In 2007, the age-standardized proportion of respondents reporting fair or poor health ranged from 12.0% (95% confidence interval (CI): 11.3, 12.7) in NHIS to 16.4% (95% CI: 15.9, 16.8) in BRFSS for males and from 13.5% (95% CI: 12.9, 14.1) in NHIS to 16.9% (95% CI: 16.6, 17.2) in BRFSS for females. NHANES estimates in 2005–2006 (the most recent available) were similar to those in BRFSS, but with greater uncertainty.
Trends in age-standardized probabilities of reporting fair or poor health are plotted in . BRFSS shows increases of 15% among women and 22% among men in reports of fair or poor health over the period 1993–2007. NHIS, on the other hand, shows reductions in fair/poor health from 1982 to 1990, followed by slight increases for the next 2–3 years. Since 1993, changes in NHIS have been relatively modest, except for a sharp drop in 1997 coinciding with a major redesign of the survey, which preserved the exact wording but relocated the self-rated health question within the survey.
Figure 1. Age-adjusted trends in self-rated health in males (A) and females (B) in 4 nationally representative surveys, United States, 1971–2007. Open circle, Behavioral Risk Factor Surveillance System; filled diamond, Current Population Survey; filled (more ...)
NHANES shows declines in fair/poor ratings from the first round of the survey (1971–1975) through the third round (1988–1994) in both sexes. In men, trends since 1999–2000 have been marked by rising reports of fair/poor health through 2003–2004, followed by a reversal of this pattern in 2005–2006; patterns for women have oscillated since 1999–2000. Finally, CPS indicates mostly steady reductions in fair/poor ratings for males since 1999 and flat trends for females over this period.
In order to consider whether differences among the surveys may apply more generally to other self-reported health-related items, we compared these results with trends in other variables. For example, presents results from NHIS, BRFSS, and NHANES for females on age-standardized proportions reporting diabetes, which are much more concordant than self-ratings of health. Results are similar for men (not shown). also presents a comparison of body mass index computed from self-reported weight and height. Although the levels and trends are similar in NHIS and BRFSS, estimates from NHANES are higher, by roughly the same increment in each year of comparison. Thus, in contrast to self-reported diabetes, self-reported body mass index appears subject to some systematic variation across surveys. Unlike self-rated health, however, the trend across surveys appears largely consistent despite variation in estimated levels.
Figure 2. Age-adjusted trends in self-reported diabetes (A) and body mass index (BMI) (B) based on self-reported weight and height among females in 3 nationally representative surveys, United States, 1971–2007. Open circle, Behavioral Risk Factor Surveillance (more ...)
Analyses by age, race, and education
Disaggregation by age, race/ethnicity, and education reveals more subtle patterns (). In the youngest age group, CPS and NHIS show the lowest fractions of respondents reporting fair or poor health. Conversely, in the oldest age group, the fraction reporting fair or poor health is highest in CPS. Overall, the sharpest divergence in trends across surveys appears in ages 20–49 years, with the proportion reporting fair/poor health in 2007 around 50% higher in BRFSS compared with NHIS or CPS, in contrast to relatively modest differences in 1993. In older age groups, differences in levels are smaller across surveys, in relative terms, but variation in time trends remains.
Figure 3. Trends in self-rated health across age, race/ethnicity, and education subgroups, United States, 1971–2007. Open circle, Behavioral Risk Factor Surveillance System; filled diamond, Current Population Survey; filled square, National Health and Nutrition (more ...)
Disaggregating by race and ethnicity, we observe the smallest inconsistencies among non-Hispanic African Americans and the largest among Hispanics. For Hispanic respondents, discrepancies among surveys have widened over time, with a nearly 2-fold difference in proportions reporting fair or poor health in NHIS versus BRFSS in 2007, compared with roughly equal proportions in the early 1990s. Levels and trends in the 4 surveys among non-Hispanic whites are moderately discrepant.
Disaggregating by educational level, the greatest discrepancies appear among those respondents without a high school diploma. The magnitudes of cross-survey differences in levels and trends between those with a high school diploma and those with at least some college are similar.
Although the poststratification weighting procedures in CPS, NHANES, and NHIS accounted for age, sex, and race/ethnicity, adjustment for race was incorporated in some states but not others in BRFSS (all states adjusted for age and sex). Education was not factored into the weights for any of the surveys. In our sample on self-rated health, we find some differences across surveys in the sample composition by race and education (Web Figure 2). Changes in these variables, however, are modest and gradual over the period of analysis, and cross-survey differences remain fairly constant over time, which suggests that discrepancies in self-rated health trends are not explained by differences in sample composition.
Alternative coding schemes for categorical self-ratings of health
Although researchers typically dichotomize self-rated health as “fair” or “poor” versus all other responses, we considered whether alternative approaches may yield more consistent results. shows trends in the 4 surveys since 1998 based on 4 different dichotomous coding schemes. (Web Figure 3 also presents trends in the average self-rated score, coding “excellent” as 5, “very good” as 4, and so on, which indicate similar discrepancies across surveys as for “fair/poor” ratings.) The ordering of the different surveys in terms of the age-standardized responses is largely preserved across the different choices of dichotomous indicator, with NHIS producing the most favorable ratings, followed by CPS, BRFSS, and NHANES; the exception is the indicator of “poor” self-ratings, for which CPS is least favorable. suggests visually that the proportion of respondents rating themselves as “excellent” may yield more consistent trends across surveys than the standard choice of “fair/poor.” This possibility is evaluated formally in the statistical models described below.
Figure 4. Age-adjusted trends in self-rated health, by category of response, United States, 1998–2007. Open circle, Behavioral Risk Factor Surveillance System; filled diamond, Current Population Survey; filled square, National Health and Nutrition Examination (more ...)
Estimated time trends, 1998–2007
For the 3 surveys with annual reporting (CPS, NHIS, BRFSS), we modeled time trends from 1998 to 2007 using logistic regression of self-rated health (with either “excellent” or “fair/poor” ratings as the dependent variable) as a function of calendar year. Separate models were fit for each survey, by subgroup. The estimated odds ratios for calendar year in the regressions were translated into average annual rates of change in the odds of reporting either “excellent” or “fair/poor” health. For example, an odds ratio of 1.02 on year implies an average annual rate of change of (1.02 − 1.00) × 100 = 2%. summarizes the regression results.
Figure 5. Average annual change in the odds of reporting “excellent” or “fair/poor” self-rated health, by sex, age, race/ethnicity, and education, United States, 1998–2007. Each bar shows the result of a separate logistic (more ...)
Overall, and in both men and women, the regressions confirm the observation that trends in “excellent” ratings are more consistent across surveys than trends in “fair/poor” ratings. In men, CPS shows significant declines in the proportion of fair/poor ratings, in contrast to the significant increases seen in BRFSS, whereas declines in excellent ratings are seen in all surveys, albeit at varying rates. Across age groups, significant differences appear in fair/poor ratings from the 2 younger age groups, while excellent ratings are less discrepant across surveys overall. Considering differences across race and ethnic groups, using either dichotomous measure, we found that the greatest discrepancies in trends appear among Hispanic respondents, especially in fair/poor responses. Finally, comparisons across education groups indicate that, for those respondents who have completed at least high school, trends are unambiguously worse: More people report “fair/poor” health at the same time that fewer people report “excellent” health. On the other hand, trends among those without a high school diploma offer the most ambiguous conclusions in any of the subgroup analyses: In terms of both the fair/poor and excellent responses, CPS points to a strong, significant favorable trend, whereas BRFSS shows a strong, significant unfavorable trend in this group.