Sedentary behavior accelerates biological aging mediated by body mass index in adults.

Sedentary behavior is widely recognized as a detriment to health. Limited conclusions have been drawn about the relationship between sitting time and biomarkers-measured aging. 12,504 eligible adults were included from the National Health and Nutrition Examination Survey (NHANES) 2007 to 2016. Weighted logistic regression, subgroup analysis, and restricted cubic spline regression were conducted to investigate the association and dose-response relationship between sitting time and phenotypic age acceleration (PhenoAgeAccel). The mediating effect of body mass index (BMI) on this correlation was revealed by mediation analysis. After adjusting for multiple covariates, longer sitting time (4-6 h: OR 1.30, 95%CI 1.06-1.58, p = 0.013; 6-8 h: OR 1.25, 95%CI 1.01-1.55, p = 0.038; ≥8 h: OR 1.58, 95%CI 1.33-1.88, p < 0.001) significantly had higher risk of aging comparing to the reference (< 4 h). The dose-response relationship exhibited an approximately linear dependence. Additionally, BMI partially mediated the association between sitting time and PhenoAgeAccel by a 21.0% proportion. Our study revealed a strong, significant, independent, linear relationship between sitting time and phenotypic age. BMI served as a mediator of the correlation between sitting time and PhenoAgeAccel.