Purpose: To investigate the coevolution of depression and health-related quality of life (HRQoL) in old age.
Methods: In a representative survey of the German general population aged 75 years and older, the course of HRQoL and depression was observed over 4.5 years (3 waves). HRQoL was assessed by the Visual Analogue Scale (EQ VAS) of the EQ-5D instrument, while the Geriatric Depression Scale was used to measure depression. A panel vector autoregressive model was used to account for the complex coevolution of depression and HRQoL. Unobserved heterogeneity was taken into account by taking the first differences.
Results: We revealed a robust negative association between an initial change in HRQoL and a subsequent change in depression score, with substantial sex differences: In women there was a robust association, while in men the significance of this association depended on the model specification. Surprisingly, in the total sample and in both sexes, no robust association between an initial increase in depression and a subsequent change in HRQoL was found.
Conclusion: Findings indicate that the direction of evolution from HRQoL to depression deserves more attention. Furthermore, treatment of depression in late life should aim at improving HRQoL in which remission of depressive symptoms is necessary but not sufficient.
Keywords: Depression; Depressive symptoms; Health-related quality of life; Longitudinal studies; Older people; Vector autoregressive model.