Abstract
BACKGROUND: Depression and anxiety are prevalent mental health disorders. While sleep duration has been extensively studied, sleep regularity may play a critical role. We aimed to examine associations between objectively measured sleep regularity and incident depression and anxiety and to investigate whether meeting recommended sleep duration modifies these associations. METHODS: In 79,666 UK Biobank participants without baseline depression or anxiety, wrist accelerometers worn for 7 days yielded a sleep regularity index (SRI) and average sleep duration. SRI was categorized as irregular (≤51), moderately irregular (52-70), or regular (≥71). Sleep duration was classified by age-specific recommendations (7-9 hours for ages 18-64 years; 7-8 hours for over 65 years). Cox regression models assessed associations between sleep parameters and mental health outcomes. RESULTS: During a median follow-up of 7.5 years, 1,646 participants developed depression, and 2,097 developed anxiety. Compared to irregular sleepers, regular sleepers had a 38% lower depression risk (hazard ratio [HR], 0.62; 95% confidence interval [CI], 0.52-0.73) and a 33% lower anxiety risk (HR, 0.67; 95%CI, 0.58-0.77). Participants with both irregular sleep and nonrecommended duration exhibited the highest risks (depression HR, 1.91; 95%CI, 1.55-2.35; anxiety HR, 1.61; 95%CI, 1.35-1.93). Notably, irregular sleepers who met duration guidelines still faced elevated risks (depression HR, 1.48; 95%CI, 1.18-1.86; anxiety HR, 1.35; 95%CI, 1.11-1.64). CONCLUSIONS: Greater sleep regularity is independently associated with lower depression and anxiety risk regardless of sleep duration, suggesting that sleep-wake consistency should be considered in mental health promotion strategies alongside traditional sleep duration recommendations.