A study by the University of San Francisco (USCF) shows that poor mental health in both early adulthood and middle age increases the risk of cognitive impairment by up to 73% (Journal of Alzheimer’s Diment, “Incident dementia and faster rates of cognitive decline are associated with worse multisensory function summary scores”, Willa D. Brenowitz, Allison R.Kaup, Kristina Yaff).
In the present study, the researchers used innovative statistical methods to predict the average course of depressive symptoms for nearly 15,000 participants aged 20 to 89, divided into three categories: elderly, middle-aged, and young adults.
They then applied these predictions and found that in a group of about 6,000 older participants, the chances of cognitive impairment were 73% higher for those estimated to have increased depressive symptoms in early adulthood and 40% higher for those who had it later in their life.
The results were adjusted to other stages of life and to different ages, genders, nationalities, educational level, body mass index, history of diabetes and smoking. The researchers found a correlation with cognitive impairment for depressive symptoms in middle age, which, however, decreased after adjusting for depression at other stages of life.
Wika Brenowitz, Ph.D., MPH, Department of Psychiatry and Behavioral Sciences, UCSF, stated: “Mechanisms such as the overactivity of the central stress response system increase the production of glucocorticoids – stress hormones – leading to damage to the hippocampus, the part of the brain responsible for creating, organizing and storing new memories.”
To assess depressive symptoms at each stage of life, the researchers compared data from younger participants with those from nearly 6,000 older people and predicted a mean course. The mean age of participants was 72 years at the start of the Study and living in their own home, and they were followed for a total of 11 years.
Although the estimated values were used, the authors point out that there are no long-term studies that have followed the lifetime of a sample. The course of depressive symptoms forms a U-shaped curve, similar to that of age-related trends in other studies. Participants were screened for depression and the findings showed that 13% of young adults, 26% of middle-aged people and 34% of the elderly had the disease.
About 1277 people were diagnosed with cognitive impairment following neuropsychological testing, evidence of global impairment, enrollment or hospitalization, for dementia as the primary or secondary diagnosis. The study concludes that the more severe the depressive symptoms, the lower the cognitive ability and the faster the rate of attenuation. The conclusion is that the elderly who have moderately high depressive symptoms in early adulthood experienced a decline in their cognitive ability over the next decade.
