Differential impacts of serum vitamin D levels and age at menarche on metabolic syndrome in premenopausal and postmenopausal women: findings from the Korea national cohort.

It is suggested that vitamin D level and age at menarche are related to each other, and the prevalence of low vitamin D status and early menarche in women is increasing worldwide. Moreover, several studies revealed that both of them are associated with metabolic syndrome (MetS). Therefore, we hypothesized that there are significant associations among vitamin D status, age at menarche, and MetS and that the relationships differ according to menstrual state. We assessed whether the association among MetS, vitamin D, and menarche age is different between premenopausal and postmenopausal women and whether there is a change in risk of MetS according to vitamin D level in different age-at-menarche groups. We used data from the Korea National Health and Nutrition Examination Survey, using 1:1 age-matching for this cross-sectional study. Individuals were stratified into 25-hydroxyvitamin D (25[OH]D) levels (deficient, <10 ng/mL; insufficient, 10-19 ng/mL; and sufficient, ≥20 ng/mL) and categorized as having either early, average, or late menarche (<13, 13-16, and ≥17 years). In premenopausal women, early menarche, not vitamin D level, was associated with risk of MetS (odds ratio [95% confidence interval], 1.65 [1.18-2.33]). In contrast, in postmenopausal women, vitamin D deficiency, not age at menarche, was associated with risk of MetS (1.39 [1.03-1.87]). In a stratified analysis regarding interactions of a change in risk of MetS according to vitamin D level in different ages at menarche, vitamin D deficiency was significantly associated with the risk of MetS (1.36 [1.01-1.86]), but this was only in the average-age-at-menarche group. This study suggests that the time of entry into puberty for women may be an important factor in the development of MetS in adulthood, and vitamin D status in women at average menarche age may contribute to the development of MetS.