Changes in Biological Markers of Health: Older Americans in the 1990s

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Abstract
Background. Many studies that show improved health in older adults have relied on subjective measures of health. This article assesses changes in the physiological status of older Americans during the 1990s using biological measures of high-risk for morbidity and mortality. Methods. Changes in the prevalence of clinically-defined, high risk for 10 biological markers were assessed in respondents age 65 years and older from National Health and Nutrition Examination Surveys (NHANES) III (1988–1994) and IV (1999–2000). Results. Some changes in prevalence of high-risk values of biological markers indicate improved health among older adults in the 1990s: a 6% reduction in the prevalence of high-risk total cholesterol (p <.001) and a 7% reduction in the prevalence of high-risk homocysteine (p <.001). Other changes indicate worsening health: a 9% increase in the prevalence of high-risk systolic blood pressure (p <.01), a 10% increase in obesity (p <.001), and an 8% increase in the prevalence of high-risk C-reactive protein (p <.001). These changes remained significant after adjusting for age, sex, and education. Results of logistic regressions indicate that changes in the frequency of medication usage, medication efficacy, prevalence of chronic disease, and diet explained some of these changes. Conclusions. Changes in the prevalence of high-risk values of biological markers in the 1990s are mixed. Greater use and effectiveness of lipid-lowering medication has contributed to the reduction in percentage of the population with high-risk lipid levels, and folate supplementation accounted for a decline in the percentage with high-risk homocysteine. However, increases in the percentage with high-risk systolic blood pressure occurred despite an increase in the use of antihypertensive medications, in part because of the limited ability of antihypertensive medications to bring blood pressure below high-risk levels.