Correlates of menstrual cycle characteristics among nulliparous Danish women

Abstract

Objective

We examined the association between lifestyle factors and menstrual cycle characteristics among nulliparous Danish women aged 18–40 years who were participating in an Internet-based prospective cohort study of pregnancy planners.

Methods

We used cross-sectional data collected at baseline to assess the association of age, body mass index (BMI), physical activity, alcohol and caffeine consumption, and smoking with the prevalence of irregular cycles, short (≤25 days) and long (≥33 days) cycles, and duration and amount of menstrual flow. We used log-binomial and multinomial logistic regression to estimate prevalence ratios and 95% confidence intervals.

Results

Low physical activity and heavy alcohol consumption were associated with an increased prevalence of irregular periods. High BMI, smoking, and caffeine and alcohol consumption were related to an increased prevalence of short menstrual cycles and heavy menstrual bleeding. Women in their mid-to-late thirties had shorter and lighter menstrual flow, but a lower prevalence of irregular cycles, compared with women 18–25 years of age.

Discussion

In this study, increased age, high BMI, and sedentary behavior were associated with menstrual-pattern irregularities. These factors may influence the balance and level of endogenous hormones conducive to optimal menstrual function.

Keywords:

• menstrual cycle
• body mass index
• alcohol drinking
• smoking
• caffeine
• physical activity
• menstruation

Acknowledgments

We are grateful to Tina Christensen for her support in data collection and media contacts, Donna Day Baird for her feedback on questionnaire development, Obi Chidi for his preliminary work on exposure categorization, and Thomas Jensen for his assistance with website and questionnaire design.

Disclosure

This study was supported by the National Institute of Child Health and Human Development (R21050264) and the Danish Medical Research Council (271-07-0338). The authors report no conflicts of interest in this work.