The role of physical activity in the bidirectional association between depressive symptoms and chronic disease incidence: A prospective analysis of the Irish longitudinal study on ageing

Aim To examine the bidirectional associations between depressive symptoms and chronic disease incidence and to investigate the moderating role of physical activity in the above-presented associations. Methods Data from the Irish Longitudinal Study on Ageing were analyzed, including 7279 participants (55.7 % women, mean age = 62.5 ± 9.2 years) across four waves (2012–2018), comprising six years of follow-up. Depressive symptoms were assessed using the 8-item Center for Epidemiologic Studies Depression scale, while chronic disease incidence covered 13 self-reported conditions. Random-intercept cross-lagged panel models examined bidirectional associations, adjusting for confounders and stratifying by baseline physical activity levels. Results A significant bidirectional association was observed between depressive symptoms and incident chronic diseases. Depressive symptoms predicted future chronic disease incidence (unstandardized beta coefficient [ B ] = 0.005; 95 %CI: 0.001–0.008), while chronic disease incidence predicted future depressive symptoms ( B = 0.216; 95 %CI: 0.100–0.331). Notably, these associations were only significant among participants with low and moderate baseline physical activity levels, where chronic diseases predicted depressive symptoms (Low baseline PA level: B = 0.006; 95 %CI = 0.001 to 0.012. Moderate baseline PA level: B = 0.008; 95 %CI = 0.002 to 0.014) and depressive symptoms predicted chronic disease incidence (Low baseline PA level: B = 0.234; 95 %CI = 0.002 to 0.466. Moderate baseline PA level: B = 0.318; 95 %CI = 0.126 to 0.511). Conclusion This study confirms bidirectional associations between depressive symptoms and chronic disease incidence. Physical activity may be a moderating factor as this bidirectional association was only significant among participants with low or moderate levels of physical activity.