What’s New in Psychology?

Depression and Cognitive Impairment in Later Life      

 Jim Windell    

           Poor cardiovascular health can damage blood flow to the brain. A decreased blow flow to the brain increases the risk for dementia. But can poor mental health also take its toll on cognition? After all, up to 20 percent of the population suffers from depression during their lifetime, might not depression play a role in cognitive aging?

           These were questions explored in a new study led by the University of California San Francisco.

           The researchers, led by first author Willa Brenowitz, Ph.D., M.P.H., of the UCSF Department of Psychiatry and Behavioral Sciences and the Weill Institute for Neurosciences, used innovative statistical methods to predict average trajectories of depressive symptoms for approximately 15,000 participants. The participants ranged in ages from 20 to 89 and were divided into three life stages: older, midlife and young adulthood. The scientists then applied these predicted trajectories.

           In estimating the depressive symptoms across each life stage, researchers pooled data from younger participants with data from the approximately 6,000 older participants and predicted average trajectories. These participants, whose average age was 72 at the start of the study and lived at home, had been enrolled by the Health Aging and Body Composition Study and the Cardiovascular Health Study. They were followed annually or semi-annually for up to 11 years.

           Participants were screened for depression using a tool called the CESD-10, a 10-item questionnaire assessing symptoms in the past week. Moderate or high depressive symptoms were found in 13 percent of young adults, 26 percent of midlife adults and 34 percent of older participants. About 1,277 participants were diagnosed with cognitive impairment following neuropsychological testing, evidence of global decline, documented use of a dementia medication or hospitalization with dementia as a primary or secondary diagnosis.

           The study found that in a group of approximately 6,000 older participants, the odds of cognitive impairment were 73 percent higher for those estimated to have elevated depressive symptoms in early adulthood, and 43 percent higher for those estimated to have elevated depressive symptoms in later life.

           These results, recently published in the Journal of Alzheimer's Disease, were adjusted for depressive symptoms in other life stages and for differences in age, sex, race, educational attainment, body mass index, history of diabetes and smoking status. For depressive symptoms in midlife, the researchers found an association with cognitive impairment, but this was discounted when they adjusted for depression in other life stages.

           According to Willa Brenowitz, “Several mechanisms explain how depression might increase dementia risk. Among them is that hyperactivity of the central stress response system increases production of the stress hormones glucocorticoids, leading to damage of the hippocampus, the part of the brain essential for forming, organizing and storing new memories.”

          Other studies have linked depression with atrophy of the hippocampus, and one study has shown faster rates of volume loss in women, she explained. While assumed values were used, the study indicates, no longitudinal studies have been completed across the life course. “Imputed depressive symptom trajectories fit a U-shaped curve, similar to age-related trends in other research,” the researchers noted.

           “Generally, we found that the greater the depressive symptoms, the lower the cognition and the faster the rates of decline,” said Brenowitz, who is also affiliated with the UCSF Department of Epidemiology and Biostatistics. “Older adults estimated to have moderate or high depressive symptoms in early adulthood were found to experience a drop in cognition over 10 years.”

           This study suggests that happiness in early adulthood may protect against dementia and that depression increases the risk for cognitive decline. However, these results seem to support screening adults for depression and treating them when depressive symptoms are discovered.

           To read the original journal article, find it with this reference:

Brenowitz,W.D., Al Hazzouri, A.Z., Vittinghoff, E., Golden, S.H., Fitzpatrick, A.L., & Yaffe, K. (2021). Depressive Symptoms Imputed Across the Life Course Are Associated with Cognitive Impairment and Cognitive Decline. Journal of Alzheimer's Disease, 1 DOI: 10.3233/JAD-210588