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

Abstract

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.