Increasing serum 25-hydroxyvitamin D is associated with reduced odds of long menstrual cycles in a cross-sectional study of African American women

Abstract

To examine the association between serum 25-hydroxyvitamin D [25(OH)D] and menstrual cycle length and regularity. Community-based, cross-sectional study of serum 25(OH)D (adjusted for seasonal differences in timing of blood draw) and menstrual cycle length. Women aged 23-34years reported their gynecologic history. Menstrual cycles were described with four independent categories (normal, short, long, irregular). We used polytomous logistic regression to estimate the association between a doubling of seasonally adjusted 25(OH)D and the odds of each cycle category. Not applicable. A total of 1,102 African American women. Not applicable. Self-reported menstrual cycle length over the previous 12months, excluding women who were using cycle-regulating medications over the entire year. Women who reported that their cycles were "too irregular to estimate" were classified as having irregular cycles. A typical cycle length of <27days was considered "short," >34days was "long," and 27-34days was "normal." The median 25(OH)D level was 14.7ng/mL (interquartile range, 10.9-19.6ng/mL). A doubling of 25(OH)D was associated with half the odds of having long menstrual cycles: adjusted odds ratio (aOR) 0.54, 95% confidence interval (CI) 0.32-0.89. 25-Hydroxyvitamin D was not associated with the occurrence of short (aOR 1.03, 95% CI 0.82-1.29) or irregular (aOR 1.46, 95% CI 0.88-2.41) menstrual cycles. Results were robust to several sensitivity analyses. These findings suggest that vitamin D status may influence the menstrual cycle and play a role in ovarian function. Further investigation of 25(OH)D and ovarian hormones, and prospective studies of 25(OH)D and cycle length, are needed.