Poor cardiovascular health has been proven to impair blood flow to the brain, increasing the chance of dementia. However, a recent study conducted by UC San Francisco suggests that poor mental health may also impact cognition and hence dementia.
While prior studies have shown a connection between depression and dementia in later life, the UCSF study demonstrates that depression in early adulthood may result in impaired cognition ten years later and cognitive decline in old age.
In predicting the typical trajectories of depressive symptoms for roughly 15,000 individuals aged 20 to 89, the researchers utilized novel statistical techniques split into three life phases: older, midlife, and early adulthood. The participants were divided into these three life stages. It was observed that among an estimated 6,000 older participants, the chances of cognitive impairment were 73% higher for those assessed to have increased depression symptoms in early adulthood and 43% higher for individuals projected to have elevated depressive symptoms in later life.
These findings were modified to account for the presence of depressive symptoms at various points in life and variations in age, gender, race, educational level, BMI, diabetes history, and smoking status. In addition, the researchers discovered a link between midlife depression and cognitive decline, but this was ruled out when they took other life phases of depression into account.
High levels of the stress hormone cortisol may impair the ability to form new memories in the future.
Researchers from UCSF's Psychiatry and Behavioral Sciences Department and the UCSF Weill Institute for Neurosciences believe depression may raise the risk of dementia in several ways. According to the study, the hippocampus, a brain region critical for creating, organizing, and storing new memories, is damaged when the central stress response system is overactive.
According to her, other research has connected depression to hippocampal shrinkage, and one study found that women had quicker volume loss.
Researchers combined younger individuals' data with roughly 6,000 older people to estimate depression symptoms throughout life stages and typical forecast trajectories. Participants in the Health Aging and Body Composition Study and the Cardiovascular Health Study began with participants who were 72 years old on average and who lived at home and had enrolled them. For up to 11 years, they were examined on a yearly or semi-annual basis.
Despite the use of assumed values, the authors noted that no life-course studies had yet been conducted. However, researchers have shown that depression symptoms tend to follow a U-shaped pattern as people age in other studies.
The CESD-10, a 10-item questionnaire used to evaluate recent depressive symptoms, screened participants for the condition. Thirteen per cent of young people, twenty-six per cent of midlife adults, and thirty-four per cent of elderly individuals had moderate or high depressive symptoms.
Neuropsychological testing, evidence of global decline, recorded use of a dementia drug, or hospitalization with dementia as a primary or secondary diagnosis led to the diagnosis of cognitive impairment in about 1,277 of the study's participants.
UCSF epidemiologist and biostatistician Brenowitz says, "Generally, we observed that higher depression symptoms led to poorer cognitive and quicker decline rates. In addition, there was a decline in cognition in older people who had moderate or high depression symptoms as young adults.
According to Kristine Yaffe, MD, senior author of the study and professor in the UCSF departments of Psychiatry and Behavioral Sciences as well as Epidemiology and Biostatistics, up to 20% of the population suffers from depression at some point in their lives, so understanding its role in cognitive ageing is critical. Of course, it'll take more study to validate these results, but in the meanwhile, screening and treating depression should be the standard operating procedure for a variety of reasons.