From nighttime light exposure to menstrual health: a critical review of evidence, mechanisms, and nursing interventions.

With the rapid progression of urbanization and the widespread adoption of nocturnal work and lifestyle patterns, artificial light at night (ALAN) has emerged as a significant environmental factor impacting women's health. Current research suggests that exposure to artificial light disrupts human circadian rhythms, potentially leading to irregular menstrual cycles, extended cycle durations, and altered hormone levels in women, thereby elevating reproductive health risks. This paper reviews epidemiological evidence concerning the impact of ALAN on menstrual cycles, critically evaluating the strength and limitations of evidence derived from different study designs. It further analyzes the mechanisms through which key parameters-including light intensity, spectral composition, and duration of exposure- influence circadian rhythms and endocrine systems, while explicitly noting that these mechanisms are largely derived from animal models and must be extrapolated to humans with caution. Furthermore, by integrating recent findings from nursing research, we propose evidence-based, tiered intervention strategies, encompassing health education, personalized lighting management, and lifestyle modifications, to mitigate potential disruptions caused by ALAN. The review aims to provide theoretical support and practical guidance for clinical nursing practices and public health policy formulation, and to highlight priority directions for future research.