Highlights • History of depression interacted with allostatic load to predict a 9-year decline in cognition in midlife. • This interaction significantly predicted executive function but not episodic memory loss. • Depression predicted cognitive decline specifically in individuals with higher than average allostatic load. • Analysis of individual physiological domains revealed that inflammation is the most important moderator. |
New research provides evidence that markers of inflammation, lipid metabolism, and body composition play a key role in predicting the likelihood of cognitive decline among depressed middle-aged adults. The study, published in Psychoneuroendocrinology , found that a history of depression interacted with allostatic load to predict a decline in cognitive performance.
Allostatic load is a measure of the cumulative damage that occurs as a result of chronic stress. It includes factors such as high blood pressure and high levels of inflammation. Managing allostatic load is essential to maintaining good health. Many studies have indicated that having a high allostatic load is associated with poorer cognitive performance. But those previous works did not assess depression, leaving open questions about the nature of the combined effects of allostatic load and depression on cognition.
Background
Allostatic load (AL) indicates the cumulative impact of stress on homeostatic mechanisms. Depression and AL have been associated with cognitive deficits, but it is unclear whether they do so independently.
Methods
Using data from middle-aged participants in the Midlife in the United States (MIDUS) longitudinal observational study (n = 704, 57.5% female, 63.8 ± 10.6 years in 2014), we assessed whether the effect of prior depression (Composite International Diagnostic Short Form Interview in 1995) on cognitive decline between 2004 and 2013 (composite Z scores derived from the Brief Test of Adult Cognition by Telephone and the Stop & Go Switch Task) was moderated by the scores Z of allostatic load (AL) in 2004 (calculated from biomarkers in blood, urine and electrocardiography).
Results
A significant depression × AL interaction predicted a decrease in a composite cognitive score (β = -0.066, SE = 0.029, p = 0.024) and executive function (β = -0.068, SE = 0.025, p = 0.007).
Depression predicted a decline in composite cognition among those with AL Z scores greater than −0.055. The AL subdomains of inflammation and lipid metabolism showed evidence of moderation.
Conclusion
Middle-aged adults with depression who had higher allostatic load had a higher risk of cognitive decline.
Future studies should evaluate whether the interaction predicts incident dementia and whether interventions targeting depression or elevated AL in people who have both can attenuate cognitive decline.
