Is age of menarche directly related to vitamin D levels?

Introduction Very few studies have examined the direct link between age of menarche and vitamin D level and controversial results have been reported. This study aimed to investigate the association between vitamin D and age of menarche in a group of adolescent girls in an area with plenty of sunshine. Methods At baseline, data were collected on 722 middle schoolgirls that were randomly selected by probability proportional to size sampling method. Of this group, 598 were followed including 173 who had their menarche during the follow-up. Serum 25-hydroxyvitamin D (25OHD) was measured at baseline using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Data on potential confounders were collected at baseline from the parents using self-administered questionnaire and from schoolgirls through face-to-face interview. Multiple linear regression and time-to-event analysis were used to investigate the association between 25OHD concentration and age of menarche. Results The mean (SD) age of the study group was 12.51 (0.91) years while the main (SD) age of menarche was 11.82 (1.04) years. The prevalence of vitamin D deficiency (<50 nmol/L) among schoolgirls was 91.69%. We found no evidence for the association between 25OHD levels and age of menarche before (beta, .00, 95% confidence interval (CI) [-0.01, 0.01]; p = .808) or after (beta, .00, 95% CI [-0.01, 0.01]; p = .765) adjusting for potential confounders. We also found no evidence for association between 25OHD status and age of menarche before (p = .424) or after (p = .356) adjusting for potential confounders. Time-to-event analysis showed no association between 25OHD level or status and age of menarche (p = .850). Conclusion In Middle Eastern setting, where vitamin D deficiency is common despite plenty of sunshine, vitamin D is not a major determinant of the age at menarche. Regardless of the link between vitamin D and age of menarche, there are several other health benefits of having adequate vitamin D level during childhood and adolescence.