Long or irregular menstrual cycles and risk of prevalent and incident non-alcoholic fatty liver disease

Context
The association of menstrual cycle length and irregularity with the risk of non-alcoholic fatty liver disease (NAFLD) is unknown. We examined this association in large cross-sectional and cohort studies.
Methods
The cross-sectional study included 72,092 women aged <40 years who underwent routine health examinations; the longitudinal analysis included the subset of 51,118 women without NAFLD at baseline. Long or irregular cycles were defined as menstrual cycles of ≥40 days or too irregular to estimate. Abdominal ultrasonography was performed to identify NAFLD. Multivariable Cox proportional hazard regression analyses were performed to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for incident NAFLD according to menstrual cycle regularity and length, with 26–30-day cycles as the reference.
Results
At baseline, 27.7% had long or irregular menstrual cycles and 7.1% had prevalent NAFLD. Long or irregular menstrual cycles were positively associated with prevalent NAFLD. During a median follow-up of 4.4 years, incident NAFLD occurred in 8.9% of women. After adjustment for age, body mass index, insulin resistance and other confounders, the multivariable-adjusted HR for NAFLD comparing long or irregular menstrual cycles to the reference group was 1.22 (95% CI, 1.14–1.31); this association strengthened in the time-dependent analysis with HR of 1.49 (95% CI, 1.38–1.60).
Conclusions
Long or irregular menstrual cycles were associated with increased risk of both prevalent and incident NAFLD in young, premenopausal women. Women with long or irregular menstrual cycles may benefit from lifestyle modification advice to reduce the risk of NAFLD and associated cardiometabolic diseases.