Associations between Superoxide Dismutase, Malondialdehyde and All-Cause Mortality in Older Adults: A Community-Based Cohort Study

Abstract

Background: In vitro and in vivo studies have suggested that some biomarkers of oxidative stress, such as superoxide dismutase(SOD), may protect against oxidative damage. This study aimed to evaluate the associations between biomarkers of oxidative stress, including plasma SOD activity and malondialdehyde(MDA), with all-cause mortality in older adults. Methods: This is a community-based cohort study of 2,224 participants(women:1227, median age: 86 years). We included individuals aged 65 or above and with plasma SOD activity and/or MDA tests at baseline. We evaluated the hazard ratios(HRs) and 95% confidence intervals(CIs) by multivariable Cox models Findings: We documented 858 deaths during six years of follow-up. There was a significant interaction effect of sex with the association between SOD activity and mortality(P<0.001). Compared with the lowest quintile, the risk of all-cause mortality was inversely associated with increasing quintiles of plasma SOD activity in women(P-trend<0.001), with adjusted HRs for the second through fifth quintiles of 0.73 (95% CI 0.53-1.02), 0.52(95% CI 0.38-0.72), 0.53(95% CI 0.39 -0.73), and 0.48(95% CI 0.35-0.66). There were no significant associations between SOD activity and mortality in men (P-trend=0.64), and between MDA and mortality in all participants (P-trend=0.79). Interpretation: Increased activity of SOD was independently associated with a lower all-cause mortality in older women but not in men. This epidemiological study lent support for the free radical/oxidative stress theory of aging. Funding: National Natural Sciences Foundation of China, the U.S. National Institute of Aging/United Nations Fund for Population Activities, and Claude D. Pepper Older Americans Independence Centers grant. Declaration of Interest: The authors declare that they have no conflict of interest. Ethical Approval: The study was approved by the Ethics Committee of Peking University and Duke University. Informed consent was obtained from all individual participants included in the study.