Age-Dependent Association Between Insomnia and Body Mass Index Among Young Women: Evidence from a Cross-Sectional...

Background/Objectives: Sleep disturbances, particularly insomnia, are increasingly recognized as important determinants of health. Previous studies have shown bidirectional associations between sleep quality and obesity. Limited evidence exists on the modifying role of age in the relationship between insomnia symptoms and body mass index (BMI) among women. This study aimed to evaluate the association between insomnia symptoms and BMI in women, with a specific focus on the potential effect of age. Methods: A cross-sectional study was conducted among 72 female nursing students aged 21-48 years. Data were collected via an online questionnaire including demographic, occupational, and anthropometric variables, as well as the Athens Insomnia Scale (AIS) to assess insomnia symptoms. BMI was calculated based on self-reported weight and height. Logistic and multiple linear regression models were used to evaluate the relationship between AIS scores and BMI and age. Results: Overall, insomnia severity was not directly associated with BMI in the full sample (p = 0.55). However, a significant interaction between insomnia symptoms and age was observed (p = 0.02). Among women aged ≥37 years, higher AIS scores were positively associated with BMI (β = 0.59; p = 0.06), whereas this association was absent in younger participants. Conclusions: Insomnia symptoms showed a trend toward a positive association with higher BMI, primarily among older women, suggesting an age-dependent relationship between sleep disturbances and body weight. Screening for sleep problems and promoting sleep hygiene could serve as simple, low-cost preventive strategies for maintaining metabolic health in women.