Oxidative balance and cognitive function in Chinese older adults: the mediating role of plasma 25-hydroxyvitamin D

Abstract

Rapid global ageing is increasing the burden of cognitive impairment. Oxidative stress may contribute to cognitive decline, and the oxidative balance score (OBS), which integrates dietary and lifestyle pro- and antioxidants, has an unclear relationship with cognitive function in older adults. This study aimed to investigate the association between the OBS and cognitive function among older adults and to examine potential indirect pathways through circulating oxidative stress-related biomarkers. We used data from 1891 adults aged ≥60 years who participated in the 2011–2014 Chinese Longitudinal Healthy Longevity Survey. Cognitive function was assessed using the Mini-Mental State Examination (MMSE). Oxidative stress markers, including albumin, superoxide dismutase, malondialdehyde and plasma 25-hydroxyvitamin D [25(OH)D], were measured at baseline and follow-up. Associations were examined using mixed-effects linear regression models and semi-longitudinal cross-lagged mediation analysis. The median cognitive score was 28 (interquartile range, 23–29). Each one-point higher OBS was associated with a 0·16-point higher MMSE score ( β = 0·16, 95 % CI 0·06 to 0·26), and participants in the highest OBS tertile had a 1·12-point higher MMSE score than those in the lowest tertile ( β = 1·12, 95 % CI 0·50 to 1·73). In mediation analysis, higher baseline OBS predicted lower plasma 25(OH)D at follow-up (path a = –1·015), and higher baseline 25(OH)D was associated with better cognitive scores at follow-up (path b = 0·025). The indirect effect of OBS on cognition through 25(OH)D was significant ( a × b = –0·025). OBS was positively associated with cognitive function, partially mediated by 25(OH)D. Further research is warranted to clarify these mechanisms and implications for cognitive aging.