0113 Sleep Moderates Depression and Quality of Life in People with Chronic Illnesses in South Africa & the United States

Abstract Introduction In the era of global health challenges, escalating chronic physical and mental health issues, coupled with sleep problems, threaten individual well-being and burden healthcare systems. This study evaluated the moderating role of sleep on the depression-quality of life (QOL) association in individuals aged 50+ with chronic illnesses in South Africa (SA) and the United States (US). Methods We studied 16,556 participants with at least one chronic illness (i.e., hypertension, diabetes, or cardiovascular disease). Data were drawn from the Health and Retirement International Family of Studies (N=3,379 in SA; N=13,177 in the US). To generate a sleep disturbance score, we averaged responses to three items: 'my sleep is restless' (no=0/yes=1), 'waking up too early' (rarely or never=0/sometimes=1/most of the times=2), and 'feeling rested' (most of the times=0/sometimes=1/rarely or never=2). To generate a QOL score, we summed responses to two questions about ‘life satisfaction as a whole’ (coded 2-10) and ‘position on the life satisfaction ladder’ (coded 0-10). Depressive symptoms were assessed via the 8-item Center for Epidemiological Studies-Depression scale. Pre-statistical harmonization aligned common items across the datasets, and country-specific regression analyses were conducted due to measurement non-invariance. Results After adjusting for demographic and health-related confounders, greater sleep disturbance was associated with lower QOL in SA (B=-0.52, 95% confidence interval (CI) =-0.55, -0.48) and the US (B=-0.48, 95% CI =-0.49, -0.47). Higher depression symptoms were associated with lower QOL in both SA (B=-0.26, 95% CI =-0.28, -0.25) and the US (B=-0.42, 95% CI =-0.42, -0.41). Sleep disturbance moderated the depression–QOL association in both countries, such that the negative association between depression symptoms and QOL was stronger among those with greater sleep disturbances, but moderation was much stronger in SA (B=-0.35, 95% CI =-0.38, -0.33) than in the US (B=-0.02, 95% CI =-0.02, -0.01). Conclusion The interaction of depression symptoms and sleep disturbances on lower QOL emphasizes the need to integrate routine depression/sleep disturbance screening and treatment in populations with chronic illnesses. Policy recommendations include culturally tailored sleep and depression interventions while future research recommendations include exploring the temporal interrelationships among depression symptoms, sleep disturbance, and quality of life. Support (if any)