To determine the association between serum vitamin D levels and age at menopause and reproductive lifespan in a group of US postmenopausal women.
Data from 6,326 postmenopausal US women in the National Health and Nutrition Examination Survey (NHANES) database 2001-2018 were obtained. Weighted multinomial logistic regression models were used to obtain odds ratios (OR) and 95% confidence intervals (CI). Statistical analyzes were performed using SAS (version 9.4; SAS Institute), and complex survey designs were considered.
Vitamin D deficiency was associated with a higher likelihood of early menopause (OR = 1.34, 95% CI: 1.15, 1.58; p = 0.008) and lower odds of late menopause (OR = 0.79, 95% CI: 0.52, 0.95) in the unadjusted model but not in the adjusted model. Lower vitamin D levels were associated with a higher risk of a shorter reproductive lifespan. The strongest association was seen in the first tertile of vitamin D deficiency (OR = 1.54; 95% CI: 1:29-1:83). After adjustment, the associations were somewhat weakened but remained statistically significant.
The results of this study suggest that vitamin D deficiency and inadequacy might be associated with earlier age at menopause. It may also reduce the reproductive lifespan in women. Given the cross-sectional nature of the NHANES dataset, these results should be interpreted with caution due to temporality bias. Menopausal age is a multifactorial phenomenon, and the identification of factors and their interactions should be evaluated in future studies.

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