Interactive effect of sleep duration, lifestyle factors and comorbidity on depressive symptoms: Insights from the China health and retirement longitudinal study.

Background: As population aging intensifies, depression emerges as a major global public health issue, especially affecting middle-aged and elderly individuals. While studies have investigated factors like sleep duration, physical activity, smoking, drinking habits, and comorbidity, the complex interplay and cumulative effect of these factors on the risk of depressive symptoms remain not fully understood.

Methods: This research utilizes data from the China Health and Retirement Longitudinal Study (CHARLS), encompassing observations from 2015 to 2020. The subjects included 8234 middle-aged and elderly individuals, accounting for a total of 22,570 observations. Lifestyle factors were represented by physical activity, smoking, and drinking habits, with the volume of moderate-to-vigorous physical activity (MVPA) quantified by quoting metabolic equivalents (MET). Multivariate logistic regression models were conducted for baseline analysis, and mixed-effects logistic regression models with random participant intercepts were constructed for the longitudinal analysis of the cohort. Moreover, interaction terms between these factors were included to assess their combined impact on the risk of depressive symptoms.

Results: Longitudinal analysis revealed a notable correlation between short sleep duration (<7 h) and an elevated risk of depressive symptoms, evidenced by an adjusted odds ratio (OR) of 3.13 (95 % CI: 2.73-3.74). Conversely, long sleep duration (>9 h) was not associated with a marked change in risk of depressive symptoms (OR = 1.11, 95 % CI: 0.78-1.59, p = 0.59). High levels of physical activity (192-336 MET-h/week) were significantly linked to an elevated risk of depressive symptoms (OR = 1.70, 95 % CI: 1.19-2.42). Discontinuing smoking was significantly correlated with a lower risk of depressive symptoms (OR = 0.68, 95 % CI: 0.52-0.90). Subjects with two or more concurrent conditions exhibited a substantially higher risk of depressive symptoms (OR = 3.19, 95 % CI: 3.13-3.25). Investigating the combined influence of sleep duration, lifestyle elements, and concurrent conditions revealed that enhanced physical activity levels significantly decreased risk of depressive symptoms in participants with short sleep duration, adjusting the OR from 3.16 to 0.83 (95 % CI, 0.53-1.30). Among participants with short sleep duration, smoking and alcohol consumption patterns were linked to a decreased risk of depressive symptoms, although these associations lacked statistical significance. Relative to subjects without concurrent conditions, those harboring two or more such conditions faced a significantly heightened risk of depressive symptoms in the context of short sleep duration (OR = 3.00, 95 % CI: 2.24-4.03), a risk not observed in subjects with extended sleep duration. Moderate napping (0.5-1 h) among participants with short sleep duration was found to significantly mitigate risk of depressive symptoms (OR = 0.64, 95 % CI: 0.44-0.95), whereas in subjects with prolonged sleep duration, extended napping did not significantly alter risk of depressive symptoms.

Limitations: The results, derived from a middle-aged and elderly Chinese population, may not be generalizable to other demographic groups or cultural contexts.

Conclusion: This study shows that short sleep duration, unhealthy lifestyle factors, and comorbidities significantly increase the risk of depressive symptoms in middle-aged and elderly individuals. Moderate physical activity, smoking cessation, moderate drinking, and appropriate napping can mitigate this risk, especially for those with short sleep duration. These findings highlight the need to address sleep quality, promote healthy habits, and manage comorbidities in mental health interventions for this population.