Risk for dementia more than doubled in people diagnosed with depression
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Key takeaways:
- More than 1.4 million Danish citizens with and without a depression diagnosis were studied for dementia risk.
- The risk for dementia was 2.41 times greater in those diagnosed with depression and was higher for men.
The risk for dementia was 2.41 times greater in Danish adults with diagnosed depression, an association that persisted when depression was diagnosed in early and middle life, according to research in JAMA Neurology.
“Several prior studies have examined the relationship between depression and dementia over the life course and have consistently found that depression later in life is associated with subsequent dementia,” Holly C. Elser, MD, MPH, PhD, an epidemiologist and resident physician in the department of neurology at the Hospital of the University of Pennsylvania, told Healio in an email. “We were particularly interested in understanding the association between depression and dementia persists even when depression is diagnosed earlier in adulthood, which would suggest that depression increases the risk of dementia.”
Seeking to examine the link between incident dementia and depression diagnosed in various stages of life, researchers conducted a nationwide, population-based cohort study from April 2020 to March 2023. They included 246,499 Danish adults from the general population (median age, 50.8 years; 64.7% women) who were diagnosed with depression and matched them by sex and birth year to 1,190,302 adults (64.6% women) without a depression diagnosis.
Participants were followed from 1977 to 2018, with a median follow-up of 7.89 years for participants with depression and 9.04 years for the matched cohort.
Researchers defined depression and incident dementia using ICD diagnostic codes within the Danish Psychiatric Central Research Register and Danish National Patient Registry and utilized Cox proportional hazards regression to determine associations between depression and dementia, adjusting for a range of health and socioeconomic factors. They grouped analyses by sex, age at diagnosis and years since index date.
According to results, 67.7% of participants with depression received a diagnosis prior to age 60 years, with the dementia hazard in this group 2.41 times that of the matched cohort (95% CI, 2.35-2.47).
“In our study, the rate of new dementia diagnoses among individuals diagnosed with depression was more than two times the rate of dementia diagnoses among individuals without depression,” Elser said.
Data also showed this association persisted when the time from the index date was greater than 20 to 39 years (HR = 1.79; 95% CI, 1.58-2.04) and for those who received a diagnosis in early, middle or late life (18-44 years: HR = 3.08; 95% CI, 2.64-3.58; 45-59 years: HR = 2.95; 95% CI, 2.75-3.17; 60 years or older: HR = 2.31; 95% CI, 2.25-2.38).
Further, the hazard of dementia was greater for men (HR = 2.98; 95% CI, 2.84-3.12) than for women (HR = 2.21; 95% CI, 2.15-2.27).
“The association between depression and dementia persisted even among individuals first diagnosed with depression in early- or mid-life,” Elser told Healio. “Our results therefore provide strong evidence that depression is not only an early symptom of dementia, but also that depression increases dementia risk.”