Depression and the Risk of Alzheimer's Disease in Older Adults

June 2022

Kim and colleagues noted that depression and other neuropsychiatric conditions are associated with dementia. To clarify the relationship between these 2 conditions, they explored whether a new diagnosis of depression was associated with a subsequent diagnosis of dementia.

In this study, the investigators analyzed the association between newly diagnosed depression and the severity of depression with subsequent development of Alzheimer’s disease in a large cohort of older adults by analyzing claims data from the Korean National Health Insurance Service-Elderly Cohort Database from 2002 to 2013. These data included a randomly sampled cohort available to researchers of 558,147 Koreans aged >60 years, representing 10% of the Korean population in this age-group. To examine only new diagnoses of depression and Alzheimer’s disease, they excluded patients with preexisting depression or preexisting Alzheimer’s disease and patients with Alzheimer’s disease diagnosed within the first year of a diagnosis of depression.

After the first year in the cohort, 14.9% of patients received a diagnosis of depression and 10.3% received a diagnosis of Alzheimer’s disease. Patients with depression had a much higher risk of Alzheimer’s disease than did those without depression.

The investigators also found that more severe depression was associated with a greater risk of Alzheimer’s disease compared with mild or moderate depression. Among patients with depression, the risk of Alzheimer’s disease was highest in the youngest groups.

The investigators concluded that “since we only included patients with new-onset depression, this study provides additional evidence that new-onset depression in the elderly is a risk factor for Alzheimer’s disease, and the severity of depression at the first visit is an important predictor of the development of dementia in these patients.”

The major question raised by this study and previous studies that found a link between depression and dementia is whether depression causes dementia or whether they have the same cause. The authors noted that if depression promotes dementia, early treatment for depression in older individuals may reduce the incidence of Alzheimer’s disease.

Because this study was retrospective, there were some factors the investigators could not assess, such as undiagnosed depression, alcohol consumption, and family history. They suggested that prospective longitudinal studies including these factors would be informative.

Source

Kim H, Jeong W, Kwon J, et al. Association between depression and the risk of Alzheimer’s disease using the Korean National Health Insurance Service-Elderly Cohort. Sci Rep. 2021;11(1):22591.

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