Individuals with depression have a significantly increased risk of developing dementia, and the correlation persists regardless of whether depression is diagnosed in early, middle, or late life, according to a study published in JAMA Neurology.
“Late-life depressive symptoms are associated with subsequent dementia diagnosis and may be an early symptom or response to preclinical disease. Evaluating associations with early- and middle-life depression will help clarify whether depression influences dementia risk,” the researchers wrote. They sought to identify correlations between early-, middle-, and late-life depression with incident dementia.
In a nationwide, population-based, cohort study, 246,499 Danish citizens (average age, 50.8 years; 64.6% female) with depression diagnoses were matched by sex and birth year to individuals without a history of depression. The study population was followed up from 1977 to 2018. The study’s main outcome of interest was incident dementia, which was defined using the International Classification of Diseases diagnostic codes in the Danish National Patient Registry and Danish Psychiatric Central Research Register. The investigators utilized Cox proportional hazards regression analysis to assess correlations between depression and dementia, adjusting for several factors, including education, income, cardiovascular disease, chronic obstructive pulmonary disease, diabetes, anxiety disorders, stress disorders, substance use disorders, and bipolar disorder.
The results showed that approximately two-thirds of individuals with depression were diagnosed before the age of 60. According to the findings, the risk of dementia among those diagnosed with depression was 2.41 times that of those in the comparison cohort (95% CI, 2.35-2.47). This correlation persisted among those diagnosed with depression in early, middle, or late in life. Also, the risk was greater for men (hazard ratio [HR], 2.98; 95% CI, 2.84-3.12) than for women (HR, 2.21; 95% CI, 2.15-2.27).
“Results suggest that the risk of dementia was more than doubled for both men and women with diagnosed depression. The persistent association between dementia and depression diagnosed in early and middle life suggests that depression may increase dementia risk,” the researchers concluded.