Moderating Effects of Age on the Longitudinal Associations Between IADL Disability, Self-Rated Health, and Depression Among Middle-Aged and Older Adults

Abstract

Background: The potential association and underlying mechanisms between instrumental activities of daily living (IADL) and depressive symptoms in middle- and older-aged adults remain unclear. This study explores the bidirectional relationship between IADL disability and depressive symptoms among Chinese middle-aged and older adults and examines the mediating or moderating effects of self-rated health (SRH) and age on this relationship. Methods: We used data from five waves (2011, 2013, 2015, 2018, and 2020) of the China Health and Retirement Longitudinal Study (CHARLS), a nationally representative survey. A total of 4830 participants aged 45 and older were included in the analysis. Longitudinal associations between IADL disability, SRH, and depressive symptoms were tested using cross-lagged models to simultaneously evaluate the bidirectional association and the strength of the temporal association. Results: Among middle-aged and older adults, there was a significant bidirectional longitudinal relationship between IADL disabilities and depressive symptoms. Higher levels of IADL disability predicted an increased risk of depressive symptoms and vice versa. SRH mediated the bidirectional relationship between IADL disabilities and depressive symptoms. Higher levels of IADL disability led to lower SRH, which further increased the risk of depressive symptoms and vice versa. Age moderated the cross-lagged models, indicating that the effect of SRH on the bidirectional relationship between IADL disability and depressive symptoms was stronger in the middle-aged group than that in the older group. Conclusion: The study results clarified the bidirectional relationship between IADL disability and depressive symptoms in middle-aged and older adults. Healthcare providers can use the findings to design targeted interventions to address the decline in IADL function and potentially benefit mental health. Helping middle-aged and older adults improve their SRH may interrupt the vicious cycle linking IADL disability and depressive symptoms, particularly in middle-aged adults transitioning to old age.