Higher sleep quality predicts lower risk of depressive symptoms: A prospective analysis from the English longitudinal study of ageing

BACKGROUND: Sleep disturbances are common in older adults and increase the risk of depression. Although several longitudinal studies have examined this relationship, few have focused on subjective sleep quality and its changes in large ageing cohorts. METHODS: A total of 11,050 non-depressed participants from wave 4 (2008-2009) of the English Longitudinal Study of Ageing were followed. Sleep quality was self-reported and categorized as good, intermediate, or poor. Depressive symptoms was assessed using the CESD8 scale. Cox proportional hazards models estimated the hazard ratios (HRs) for depressive symptoms, adjusting for demographic, health, and lifestyle factors. RESULTS: Among 8425 eligible participants, intermediate sleep quality was associated with a 45% lower risk of depressive symptoms (HR = 0.55, 95% CI: 0.43-0.69), and good quality with a 69% lower risk (HR = 0.31, 95% CI: 0.24-0.40). These associations remained significant in sensitivity analyses limited to individuals with normal sleep duration. Stronger protective effects were observed in those aged 60-80 years. Moreover, participants who maintained or improved their sleep quality over time had significantly lower depressive symptoms risks than those whose sleep worsened (HR = 0.64 and HR = 0.58). CONCLUSION: Better self-reported sleep quality was independently associated with a lower risk of depressive symptoms in older adults. While causality cannot be inferred, these findings highlight sleep quality as a potentially modifiable target for depression prevention in ageing populations.