Oxidative Balance Score Is Associated with Social Involvement and Weight-Adjusted Appendicular Skeletal Muscle Mass in Middle-Aged and Older Japanese Women

Background: The oxidative balance score (OBS) is an indicator for assessing total oxidant status. This cross-sectional study aimed to investigate the relationships between OBS and factors associated with well-being among middle-aged and elderly women. Methods: Dietary habits, lifestyle factors, and factors associated with well-being, including physical, mental, and social health, were assessed based on the first-visit medical records in 385 Japanese women. The OBS was calculated using pro-oxidant factors (fat, saturated fatty acids, n-6 polyunsaturated fatty acids, iron, alcohol, smoking, body mass index, and waist circumference) and antioxidant factors (zinc, vitamins C, E, A, n-3 polyunsaturated fatty acids, genistein, and exercise). Results: After adjusting for age, menopausal status, and background factors, social engagement and weight-adjusted appendicular skeletal muscle mass (ASM/Wt) were found to be significantly associated with OBS (social involvement, odds ratio = 0.882, 95% confidence interval [CI] = 0.817–0.949, p = 0.001; ASM/Wt, odds ratio = 0.983, 95% CI = 0.974–0.990, p < 0.001). Conclusions: Higher oxidative stress was associated with a low level of social involvement and ASM/Wt. These findings indicate that oxidative balance is linked to social and physical aspects of well-being among middle-aged and older women. However, because of the cross-sectional design, causal relationships cannot be inferred, and the possibility of reverse causation should be considered.