Nonlinear Association Between Oxidative Balance Score and Premature Menopause: A Cross-Sectional Analysis of NHANES 2007-2018 Data.

Background: Oxidative stress is a critical mediator in ovarian aging, a key process leading to premature menopause (PM), which is defined as menopause before age 40. While the Oxidative Balance Score (OBS), a composite measure of dietary and lifestyle pro- and anti-oxidant exposures, provides valuable insight, its association with PM remains unclear. This study aimed to investigate the association between OBS and PM in a nationally representative US population. Methods: This cross-sectional study utilized data from 4,128 participants in the National Health and Nutrition Examination Survey (NHANES) 2007-2018. The OBS was calculated from 16 dietary and 4 lifestyle components. Multivariable logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs), with all analyses accounting for the complex survey design using appropriate NHANES sample weights. The potential nonlinear relationship was explored using restricted cubic splines (RCS). Results: A higher total OBS was significantly associated with a lower risk of PM (Adjusted OR for the highest compared to the lowest quartile, 0.51; 95% CI, 0.31 to 0.83). The dietary OBS component showed a consistent inverse association. Subgroup analysis suggested potential ethnic variations, although the interaction did not reach statistical significance (P for interaction = 0.054). RCS analysis confirmed a nonlinear inverse association. Further threshold effect analysis identified a turning point at an OBS of 28; the association was significant below this threshold (OR per unit increase, 0.95; 95% CI, 0.93 to 0.97), but this was not observed above it (OR, 1.09; 95% CI, 1.00 to 1.18). Conclusion: In this nationally representative sample of US women, a higher OBS was associated with a lower risk of PM, particularly below a score of 28. These findings suggest that dietary and lifestyle factors contributing to antioxidant balance may play a role in preserving ovarian function, although prospective studies are required to confirm causality.