Allostatic load and depressive symptoms in older adults: An analysis of 12-year panel data.

Abstract

BACKGROUND: Whether changes in allostatic load (AL) and depressive symptoms relate over time has not been yet fully explored. This study evaluated the association between AL and depressive symptoms over 12 years among community-dwelling older adults. METHODS: Panel data from 8291 participants in the English Longitudinal Study of Ageing were analysed. Depressive symptoms were assessed with the 8-item Centre for Epidemiologic Studies Depression Scale (CES-D). The AL score was derived from nine metabolic, cardiovascular and immune biomarkers. The association between AL and depressive symptoms was modelled in a linear hybrid model adjusting for time-invariant (sex, ethnicity) and time-variant confounders (age, marital status, education, wealth, physical activity, smoking status, alcohol intake, limitations in daily living, comorbidities). RESULTS: The mean AL score was 3.1 (SD: 2.1), 3.5 (2.3), 3.2 (2.3) and 3.3 (2.5) whereas the mean CES-D score was 1.4 (SD: 1.8), 1.2 (1.8), 1.2 (1.8) and 1.2 (1.7) in waves 2, 4, 6 and 8, respectively. In the adjusted model, the between-person differences (coefficient: 0.02, 95% CI: 0.01, 0.04) but not the within-individual differences (0.01; 95% CI: -0.01, 0.03) in the AL score were associated with CES-D score. The between-person coefficient indicates that participants with greater AL scores also had slightly higher CES-D scores. The within-person coefficient indicates that changes in the AL score were not associated with changes in the CES-D score. CONCLUSION: AL was associated with depressive symptoms. However, most of the association was driven by differences in AL between individuals rather than changes in AL over time.