ASSOCIATION BETWEEN SLEEP REGULARITY AND SYMPTOMS OF ANXIETY AND DEPRESSION IN MIDDLE-AGED ADULTS

Abstract Background Sleep regularity plays a significant role in mental health, but its association with anxiety or depression symptoms in midlife and whether movement behaviors moderate these associations is unclear. We examined how variability in sleep timing and duration is associated with these symptoms and tested the moderating effects of physical activity and sedentary time. Methods We analyzed data from 3,556 46-year-old participants in the Northern Finland Birth Cohort 1966. Sleep regularity was derived from 7 days of accelerometer-measured sleep timing (midpoint of sleep period) and sleep duration, expressed as standard deviations and categorized as regular, moderately irregular, or highly irregular. Anxiety and depression symptoms were assessed using the Hopkins Symptom Checklist-25. Associations were examined using multivariable linear regression adjusted for gender, marital status, education, smoking, alcohol use, medication, chronotype, work schedule, and physical activity or sedentary time derived from the same accelerometer data, with moderation tested using interaction terms (B coefficients with 95% confidence intervals). Results Greater sleep timing irregularity was associated with higher anxiety symptoms (B = 0.025, 95% CI [0.007, 0.043], p = 0.001), and with depressive symptoms only when models included sedentary time (B = 0.035, 95% CI [0.017, 0.053], p < 0.001). Sleep duration irregularity showed no significant associations. Physical activity and sedentary time did not moderate these relationships. Conclusions Sleep timing regularity was more consistently associated with mental health outcomes, especially anxiety, than sleep duration variability. Maintaining regular sleep timing may support anxiety management in midlife, highlighting its potential relevance for preventive intervention.