Serum antioxidant status and mortality from influenza and pneumonia in US adults
Abstract Objective: We examined the association between serum antioxidant status and mortality from influenza and pneumonia in US adults. Design: Serum concentrations of antioxidants included vitamin C, vitamin A, vitamin E, sum of α- and β-carotene, β-cryptoxanthin, lutein+zeaxanthin, and lycopene. We computed total antioxidant capacity (TAC) as a measure of composite antioxidant status in serum. Survey-weighted Cox proportional hazard models were used to compute hazard ratios (HRs) and 95% confidence intervals (CIs) comparing quartiles of each antioxidant and TAC. Setting: Data from the US National Health and Nutrition Examination Survey (NHANES)-III. Participants: A total of 7428 NHANES-III participants ≥45 years of age. Results: With a weighted-median follow-up of 16.8 years, 154 participants died from influenza/pneumonia. After adjustment for covariates, serum vitamin C, the sum of α- and β-carotene, and TAC were non-linearly associated with influenza/pneumonia mortality, with the statistically significant smallest HRs at the third quartile vs the first quartile [HRs=0.38 (95% CI: 0.19–0.77), 0.29 (0.16–0.51), and 0.30 (0.15–0.59), respectively]. HRs comparing the fourth vs the first quartiles were weaker and non-significant: 0.57 (95% CI: 0.27–1.17), 0.70 (0.41–1.19), and 0.65 (0.31–1.35), respectively. Serum lycopene had a monotonic association with influenza/pneumonia mortality [HR=0.43 (95% CI: 0.23–0.83) comparing the fourth vs the first quartile, P-for-trend=0.01]. Conclusions: The present study suggests that antioxidant intake as reflected by serum concentrations may reduce mortality risk from influenza or pneumonia in the US general population. These findings warrant further confirmation in other populations with different settings (e.g., a shorter-term association with influenza infection).