Circadian rhythm entrainment factors and premenstrual syndrome: a cross-sectional study of the roles of light exposure, exercise, and meal timing

Premenstrual syndrome (PMS) is a common condition affecting women, involving physical and emotional symptoms. Since circadian rhythms may be disrupted during the premenstrual phase, regulating them could alleviate PMS. The purpose of this study was to determine how lifestyle factors (light exposure, exercise, and food intake) related to circadian rhythm entrainment contribute to PMS severity based on chronotype. A cross-sectional study was conducted in Japanese women aged 20–49 years. PMS severity was assessed using the Menstrual Distress Questionnaire. Lifestyle habits related to circadian entrainment were also surveyed. The final sample comprised 564 women (249 morning types and 315 evening types). Multiple regression analysis was performed with PMS score as the objective variables and lifestyle related to circadian rhythm as the independent variables. Two models addressed multicollinearity: Model 1 included natural light exposure, screen-time after sunset, and first meal timing; Model 2 included screen-time, exercise, and meal timing. Ethical approval was obtained. Among the 564 women, the numbers of reports of mild or worse PMS symptoms, were 526 (93.3%) for pain, 510 (90.4%) for water retention, 265 (47.0%) for autonomic reactions, and 482 (85.5%) for negative affect, many experienced PMS symptoms. For morning types, 4 or more hours of screen-time after sunset was associated significantly with higher negative affect scores (Model༑;β = 1.46; 95% CI, 0.09 to 2.83; p = 0.037), (Model2༛β = 1.43; 95% CI, 0.06 to 2.80; p = 0.040). For evening types, less than 2 h of daytime light exposure was associated with increased negative affect (β = 0.91; 95% CI, 0.15 to 1.66; p = 0.019) and water retention (β = 0.42; 95% CI, 0.05 to 0.79; p = 0.026). Similarly, exercise was other associated with increased water retention (β = 0.50; 95% CI, 0.14 to 0.86; p = 0.007). Meal timing was not significantly associated with any entrainment factors. These findings suggest that circadian rhythm entrainment through appropriate light exposure and exercise timing can alleviate PMS. The consideration of individuals’ chronotypes may enhance the effectiveness of lifestyle-based interventions for PMS relief.