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The Effects of Serum Beta-Carotene Concentration and Burden of Inflammation on All-Cause Mortality Risk in High-Functioning Older Persons: MacArthur Studies of Successful Aging

¹ Multicampus Program in Geriatric Medicine and Gerontology, UCLA School of Medicine, Los Angeles, California.
² Andrus Gerontology Center, University of Southern California, Los Angeles.
³ Laboratory of Epidemiology, National Institute on Aging, National Institutes of Health, Bethesda, Maryland.

Address correspondence to Peifeng Hu, MD, PhD, Multicampus Program in Geriatric Medicine and Gerontology, UCLA School of Medicine, 10945 Le Conte Avenue, Suite 2339, Los Angeles, CA 90095-1687. E-mail: phu{at}mednet.ucla.edu

Background. It remains unclear to what extent the associations between low serum beta-carotene concentration and increased risk for cardiovascular disease and cancers are attributable to inflammation. The objective of this study was to evaluate simultaneously the effects of serum beta-carotene concentration and inflammation on the subsequent all-cause mortality risk in high-functioning older persons.

Methods. The authors conducted a prospective cohort study using information from 672 participants from the MacArthur Studies of Successful Aging. Baseline information was obtained for serum concentrations of beta-carotene, C-reactive protein, interleukin-6, cholesterols, and albumin; body mass index; waist:hip ratio; prevalent medical conditions; health behaviors; and medications. Sex-specific univariate and multivariate logistic regression analyses were used to study the effects of low beta-carotene, high inflammation burden, or both on 7-year all-cause mortality rates while adjusting for other confounders.

Results. The serum beta-carotene concentration was inversely associated with C-reactive protein and interleukin-6 levels. After adjustment for inflammation markers and other covariates, the relative risks for low beta-carotene for the 7-year all-cause mortality risk were 2.30 (95% confidence interval [CI], 1.23 to 4.31) in men and 0.85 (95% CI, 0.42 to 1.75) in women. Compared with men with high beta-carotene levels and low inflammation, the multiply adjusted relative risk for low beta-carotene and high inflammation burden was 3.78 (95% CI, 1.69 to 8.47) in men.

Conclusions. Low levels of serum beta-carotene are independently associated with an increased all-cause mortality risk in older men, even after adjustment for the effects of inflammation and other risk factors. In men, but not women, a synergistic effect occurs between low beta-carotene concentration and high inflammation burden in predicting higher mortality rates.