Background: With rapid population ageing, depressive symptoms in older adults have become a pressing public health concern. While functional dependency is a known risk factor, the impact of changes in dependency over time remains unclear. Objective: To examine the association between changes in daily living dependency and incident depressive symptoms in older adults across international cohorts. Methods: We used data from 46 327 adults aged ≥50 years across four longitudinal ageing studies: China Health and Retirement Longitudinal Study (China), Health and Retirement Study (USA), English Longitudinal Study of Ageing (England) and Survey of Health, Ageing and Retirement in Europe (Europe). Daily living dependency was classified into three levels based on difficulties in activities of daily living (ADLs) and instrumental ADLs (IADLs). Change in dependency was assessed using baseline and 2-year follow-up data. Depressive symptoms were measured using the Center for Epidemiologic Studies depressive symptoms Scale or the European Depression Scales (EURO-D). Cox proportional hazard models estimated HRs and 95% CIs for incident depressive symptoms over a median follow-up of 4.2–5.1 years. Findings: A total of 12 902 new depressive symptom cases occurred during follow-up. Compared with participants whose dependency status remained unchanged, those who recovered to independency had a significantly reduced risk of depressive symptoms. Functional deterioration, including transitions from independency to ADL or IADL dependency, was associated with increased risk of depressive symptoms (both pooled HRs 1.55), while functional improvement, from ADL or IADL dependency to independency, was linked to reduced risk (HRs 0.83 and 0.80, respectively). Conclusions: Improvement in ADL dependency is linked to a lower risk of depressive symptoms, while worsening dependency significantly increases depressive symptoms risk. Clinical implications: Routine assessment of functional status and early interventions to maintain or restore daily living independency may help prevent depressive symptoms in older adults. Targeted rehabilitation and support services could play a key role in reducing the mental health burden of ageing populations.

Urban-rural differences in depression are evident among older adults in China but not in the United States. By comparing the two countries, this study aims to explore strategies for promoting regional equality in depression in China. Data from the China Health and Retirement Longitudinal Study (CHARLS) and the Health and Retirement Study (HRS) were utilized. Longitudinal data were used to describe urban-rural differences in depression prevalence among older adults in China (2011-2020) and the United States (2010-2020). Cross-sectional data from 2018 (CHARLS: 9840 participants; HRS: 10,381 participants) were used to identify key modifiable factors. A random forest algorithm was employed to determine the most important factors influencing depression, and comparisons between the two countries were made to identify modifiable factors. Multivariate logistic regression was used to analyze the relationship between these key modifiable factors and depression. A mediation model was applied to assess the mediating role of key modifiable factors in the relationship between residence and depression. 1) From 2011 to 2020, Urban-rural differences in depression prevalence among older adults were observed in China, but not in the United States. 2) In both China and the U.S., the top five factors ranked by importance were activities of daily living disability (ADLs), instrumental activities of daily living disability (IADLs), pain levels, self-reported health (SRH), and age. However, Urban-Rural Differences in ADLs, IADLs, and SRH were present in China but not in the United States. 3) ADLs, IADLs, and SRH collectively mediated 31.6 % (95 % CI: 0.268 - 0.360) of the relationship between residence and depression scores among older adults in China. Urban-rural differences in physical health status (ADLs, IADLs, and self-reported health) among older adults in China are associated with Urban-Rural Differences in depression. The absence of such inequalities in the U.S. may offer insights for developing policies to promote regional equality in depression among older adults in China.

Background: The aim of this study is to explore the independent and joint associations between physical activity (PA) and sleep duration with depressive symptoms. Methods: We included and analyzed 18,052 participants (age ≥ 20 years) from the cross-sectional National Health and Nutrition Examination Survey (NHANES) conducted between 2007 and 2014. Results: After adjustment, both males and females showed a significant correlation between PA, sleep duration, and depressive symptoms. In the joint association analysis, we found: 1. The interaction between PA and sleep duration was statistically significant in males but not significant in females (P=0.380). 2. Compared to individuals with the lowest PA level and not meeting the National Sleep Foundation's (NSF) guidelines, those with the highest PA level and recommended sleep duration had a 79% decrease in depression risk in males (odds ratio [OR] 0.21, 95% confidence interval [CI] 0.14-0.32) and a 74% decrease in females (OR 0.26, 95% CI 0.20-0.35). 3. In male participants adhering to NSF guidelines, each increase in PA quartile is associated with a 19% reduction in the risk of depression (OR 0.81, 95% CI 0.71-0.92). Conversely, among male participants not adhering to NSF guidelines, there is a 23% decrease in depression risk (OR 0.77, 95% CI 0.69-0.86). For female participants, the respective reductions in depression risk are 20% (OR 0.80, 95% CI 0.73-0.89) and 14% (OR 0.86, 95% CI 0.80-0.93). Conclusion: For males, adherence to recommended sleep duration weakens the relationship between physical activity and depression, while the opposite is observed for females.