Elsevier

Annals of Epidemiology

Volume 20, Issue 10, October 2010, Pages 743-749
Annals of Epidemiology

Does Self-Rated Health Mean the Same Thing Across Socioeconomic Groups? Evidence From Biomarker Data

https://doi.org/10.1016/j.annepidem.2010.06.007Get rights and content

Purpose

Self-rated health (SRH) is widely used to study health inequalities by socioeconomic status (SES), but concern has arisen that SRH may not correspond to objective health in the same way for different SES groups. We test whether levels of biological risk differ by SES for those with the same SRH.

Methods

We analyzed a U.S. nationally representative sample of 13,877 adults aged 25 to 80 years. We tested whether education modifies the association between SRH and 14 biomarkers representing metabolic, cardiovascular, inflammatory, and organ function using both interaction models and models stratified by four levels of SRH. Estimated education coefficients in the stratified models indicated whether biomarker levels varied by educational attainment within a given self-rated health category.

Results

Significant variation in biological risk by education within the same self-rated health category was found, especially at higher levels of SRH. In general, respondents with more education had healthier levels of biomarkers for the same level of SRH.

Conclusions

The results suggest that the relation of self-reported health to objective health, as measured by biological risk factors, differs by socioeconomic status. Caution should be exercised when using SRH to compare health risks across SES groups.

Introduction

Self-rated health (SRH) status on a five-point scale has been used extensively in the study of health inequalities by socioeconomic status (SES), based partly on its ease of collection and consistent associations with subsequent morbidity and mortality 1, 2, 3. Concerns have arisen, however, that the measurement of health inequalities with SRH may be biased if individuals from different socioeconomic groups have systematically different expectations or reporting standards for health, sometimes called “reporting heterogeneity” 4, 5. Recently, other investigators have examined whether equivalent SRH translates into the same “objective” health status across different socioeconomic groups by testing whether the association of SRH with mortality risk varies by SES. Results have been mixed; SRH was a stronger predictor of mortality for higher SES groups in the United States and the Netherlands, a weaker predictor for higher SES groups in France, and an equal predictor across SES in Sweden and the United Kingdom 6, 7, 8, 9, 10, 11, 12. Several investigators also have found evidence for reporting heterogeneity by SES by using alternative benchmarks for “objective” health such as self-reported clinical illnesses or physical functioning 13, 14, or the more detailed self-reported MacMaster Health Utility Index and SF-36 instrument 4, 15.

Profiles of biological risk present a promising “objective” benchmark for SRH with several advantages over mortality risk or other self-reported measures such as functional limitations or chronic conditions. The use of self-reported conditions or functional limitations as a benchmark for SRH cannot rule out reporting heterogeneity that may be shared by both sets of self-reports. The use of clinical or physician-reported illness as a benchmark also suffers from potential biases resulting from differential access to care and probability of diagnoses. Biomarkers, in contrast, are measured in the laboratory and avoid this type of systematic reporting error. Although a few researchers have investigated the relation of biomarkers to SRH 16, 17, 18, only one study to our knowledge has tested whether levels of biomarkers across SRH categories vary by SES. In the United Kingdom, average measures of body mass index (BMI) and blood pressure across two categories of SRH were found to differ between manual versus nonmanual worker categories for women but not for men (19).

We aimed to expand upon this work by analyzing a broader array of biomarkers and a wider range of SRH and SES categories in a large, nationally representative U.S. sample. We tested whether levels of important markers of metabolic, cardiovascular, and inflammatory risk and organ functioning vary by education for adults reporting the same category of SRH. These results will contribute evidence to the nature of reporting differences in SRH and improve our understanding of the strengths and potential biases of SRH as a measure of population health.

Section snippets

Methods

Data are from the Third National Health and Nutrition Examination Survey (NHANES III), conducted by the U.S. National Center for Health Statistics between 1988 and 1994. NHANES III is a cross-sectional stratified multistage probability sample of the civilian noninstitutionalized U.S. population age 2 months to 90 years. Data were collected in household interviews, clinical examinations, and laboratory tests. Details of the sampling design and protocol have been previously reported 20, 21.

We

Results

Descriptive statistics for the sample are shown in Table 1. A total of 21% of respondents reported “excellent” health, 30.4% “very good,” 32.3% “good,” 13.0% “fair,” and 3.3% “poor.” Mean levels of biomarkers across four categories of SRH are shown separately in Table 2 for men and women. For almost all markers, mean levels differed significantly across SRH categories in the expected direction. Those reporting worse health had greater levels of systolic and diastolic BP, BMI, waist-hip ratio,

Discussion

Using data from a nationally representative U.S. sample, we identified differences in biological risk within SRH categories by education, especially for higher levels of SRH. These results provide evidence that a given level of SRH may not translate into the same objective health for different SES groups and suggest that researchers should use caution in interpreting differences in SRH by SES.

Strengths of this study include the use of a large, nationally representative sample of the

References (29)

  • E.L. Idler et al.

    Self-rated health and mortality: A review of twenty-seven community studies

    J Health Social Behav

    (1997)
  • E.L. Idler et al.

    Survival, functional limitations, and self-rated health in the NHANES I epidemiologic follow-up study, 1992

    Am J Epidemiol

    (2000)
  • K.B. DeSalvo et al.

    Mortality prediction with a single general self-rated health question. A meta-analysis

    J General Intern Med

    (2006)
  • A. Quesnel Vallee

    Self-rated health: Caught in the crossfire of the quest for ‘true’ health?

    Int J Epidemiol

    (2007)
  • Cited by (0)

    View full text