Late-life depression and multimorbidity trajectories: the role of symptom complexity and severity.

Introduction: as late-life depression is associated with poor somatic health, we aimed to investigate the role of depression severity and symptom phenotypes in the progression of somatic multimorbidity.

Methods: we analysed data from 3,042 dementia-free individuals (60+) participating in the population-based Swedish National Study on Aging and Care in Kungsholmen. Using the baseline clinical assessment of 21 depressive symptoms from the Comprehensive Psychopathological Rating Scale, we: (i) diagnosed major, minor (in accordance with DSM-IV-TR) and subsyndromal depression; (ii) extracted symptom phenotypes by applying exploratory network graph analysis. Somatic multimorbidity was measured as the number of co-occurring chronic diseases over a 15-year follow-up. Linear mixed models were used to explore somatic multimorbidity trajectories in relation to baseline depression diagnoses and symptom phenotypes, while accounting for sociodemographic and behavioural factors.

Results: in multi-adjusted models, relative to individuals without depression, those with major (β per year: 0.33, 95% confidence interval [CI]: 0.06-0.61) and subsyndromal depression (β per year: 0.21, 95%CI: 0.12-0.30) experienced an accelerated rate of somatic multimorbidity accumulation, whereas those with minor depression did not. We identified affective, anxiety, cognitive, and psychomotor symptom phenotypes from the network analysis. When modelled separately, an increase in symptom score for each phenotype was associated with faster multimorbidity accumulation, although only the cognitive phenotype retained its association in a mutually adjusted model (β per year: 0.07, 95%CI: 0.03-0.10).

Conclusions: late-life major and subsyndromal depression are associated with accelerated somatic multimorbidity. Depressive symptoms characterised by a cognitive phenotype are linked to somatic health change in old age.