Happiness in early adulthood may protect against dementia

Depressive symptoms increase risk for cognitive impairment

A recent study conducted by the University of California, San Francisco (UCSF) suggests that poor mental health may also have an impact on cognition. Previous research has shown that poor cardiovascular health may impair blood flow to the brain, raising the risk of dementia. The findings add to a growing body of evidence linking depression to dementia. However, while most studies have focused on the association between depression and dementia in later life, the UCSF study shows that depression in early adulthood may result in lower cognition ten years later and cognitive decline in old age, respectively. On September 28, 2021, the Journal of Alzheimer’s Disease will publish the findings of this research.

Roughly 15,000 individuals, ranging in age from 20 to 89, were split into three life stages: elderly, midlife, and early adulthood. The researchers utilized novel statistical techniques to predict typical trajectories of depressive symptoms for approximately 15,000 people. Once these predicted trajectories were applied, the researchers discovered that, in a group of approximately 6,000 older participants, the odds of cognitive impairment were 73 percent higher for those who were estimated to have elevated depressive symptoms in early adulthood, and 43 percent higher for those who were estimated to have elevated depressive symptoms later in life. These findings were adjusted to account for depressed symptoms experienced at other periods of life as well as variations in age, gender, race, educational attainment, body mass index, history of diabetes, and tobacco use. The researchers discovered a link between depressed symptoms in midlife and cognitive impairment, but this was dismissed when they took into account depression in other life phases as well as sadness in midlife.

Excess stress hormones may impair one’s ability to form new memories in the future. “A number of processes explain why depression may raise the risk of dementia,” said Willa Brenowitz, PhD, MPH, of the University of California, San Francisco Department of Psychiatry and Behavioral Sciences and the Weill Institute for Neurosciences, who was first author on the study. In particular, hyperactivity of the central stress response system leads to increased production of the stress hormones glucocorticoids, which in turn causes damage to the hippocampus, which is a critical region of the brain involved in the formation, organization, and storage of new memories.

Another research found a connection between sadness and atrophy of the hippocampus, and one study found that women have quicker rates of volume loss than males, she said. Researchers combined data from roughly 6,000 younger individuals with data from approximately 6,000 older participants to estimate the prevalence of depressive symptoms throughout each life stage. They then projected typical trajectories. The Health Aging and Body Composition Study and the Cardiovascular Health Study had both recruited these individuals, who had an average age of 72 at the time of the study’s inception and were living at home at the time of enrollment. They were followed up on on an annual or semi-year basis for up to 11 years in total.

The U-Shaped Curve Increases the Credibility of Predicted Trajectories

According to the authors, although assumed values were utilized, no longitudinal studies throughout the life cycle had been performed at the time of writing. As the researchers pointed out, “imputations of depressed symptoms traced out a U-shaped curve, which is consistent with age-related patterns in previous studies.” Participants were tested for depression using a technique called the CESD-10, which is a ten-item questionnaire that assesses symptoms experienced in the previous seven days. Thirteen percent of young people, 26 percent of midlife adults, and 34 percent of older individuals had moderate or severe depression symptoms, according to the study. Following neuropsychological testing, evidence of global decline, recorded use of a dementia medication, or admission to the hospital with dementia as a main or secondary diagnosis, a total of 1,277 individuals were identified as having cognitive impairment.

The study’s lead author, Brenowitz, is also associated with the University of California, San Francisco Department of Epidemiology and Biostatistics. “In general, we observed that the higher the severity of depressive symptoms, the poorer the cognition and the quicker the rates of decline,” he added. “It was discovered that older people who were assessed to have moderate or high depression symptoms in early adulthood had a decline in cognition over a 10-year period.” Due to the fact that up to 20% of the population will suffer from depression at some point in their lives, it is critical to recognize depression’s role in cognitive aging, according to senior author Kristine Yaffe, MD, from the University of California, San Francisco (UCSF) departments of Psychiatry and Behavioral Sciences, and Epidemiology and Biostatistics. “Future research will be required to validate these results, but in the meanwhile, depression should be screened for and treated for a variety of causes.”

Reference : Willa D. Brenowitz, Adina Zeki Al Hazzouri, Eric Vittinghoff, Sherita H. Golden, Annette L. Fitzpatrick, Kristine Yaffe. Depressive Symptoms Imputed Across the Life Course Are Associated with Cognitive Impairment and Cognitive DeclineJournal of Alzheimer’s Disease, 2021; 1 DOI: 10.3233/JAD-210588

Categories: Clinical