The longitudinal association between depressive symptoms and functional abilities in older patients

Objectives: To investigate the course of depressive symptoms, and basic and instrumental activities of daily living (collectively described as, (I)ADL functioning) from acute admission until one year post-discharge, the longitudinal association between depressive symptoms and (I)ADL functioning, and to disaggregate between- and within-person effects to examine whether changes in depressive symptoms are associated with changes in (I)ADL functioning. Methods: Prospective multicenter cohort of acutely hospitalized patients aged ≥70. Data gathered over a one-year period were assessed using validated measures of depressive symptoms (GDS-15) and physical functioning (Katz-ADL index). A Poisson mixed model analysis was used to examine the association between the courses and a hybrid model was used to disentangle between- and within-subject effects. Results: The analytic sample included 398 patients (mean age = 79.6 years, SD = 6.6). Results showed an improvement in depressive symptoms and physical functions over time, whereby changes in depressive symptoms were significantly associated with the course of ADL function (rate ratio (RR) = 0.91, p <.001) and IADL function (RR = 0.94, p <.001), even after adjustment for confounding variables. Finally, both between- and within-person effects of depressive symptoms were significantly associated with the course of ADL function (between-person: RR = 0.85, p <.001; within-person: RR = 0.94, p <.001) and IADL function (between-person: RR = 0.87, p <.001; within-person: RR = 0.97, p <.001). Conclusion: The course of depressive symptoms and physical functions improved over time, whereby changes in depressive symptoms were significantly associated with changes in physical functions, both at group and individual level. These changes in (I)ADL functioning lie mostly above the estimated minimally important change for both scales, implying clinically relevant changes.