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Dementia risk was higher in people who had signs of psychological distress earlier in life, a cohort study in Finland found.

In more than 67,000 people with an average age of 45, self-reported distress symptoms -- notably, stress, and exhaustion -- were associated with a 17% to 24% increased risk of dementia over a 25-year follow-up period, reported Sonja Sulkava MD, PhD, of the Finnish Institute for Health and Welfare in Helsinki, and co-authors.

These self-reported symptoms were tied to an 8% to 12% increase in lifetime dementia after accounting for the competing risk of death, which was more common than dementia over time, Sulkava and colleagues wrote in .

"Our study suggests symptoms of psychological distress like exhaustion, depressive mood, and the experience of stress are risk factors for dementia, and not only prodromal symptoms of underlying dementia disorder," Sulkava wrote in an email to 番茄社区.

"Previous studies have shown an association between symptoms of psychological distress and dementia, but the nature of the association is still unclear," Sulkava wrote. "We clarified that connection using a large population data set with 10 to 45 years of follow-up and careful modeling of death for other causes."

The study used data from 67,688 people who completed National FINRISK Study surveys between 1972 and 2007. Participants self-reported symptoms of psychological distress in the prior month, including whether they experienced stress more than other people and whether they experienced depressive mood, exhaustion, and nervousness often, sometimes, or never. The cohort was linked to the Finnish Health Register for dementia and mortality data.

About half (51.7%) of participants were women. Baseline ages ranged from 25 to 74 years, with a mean age of 45.4. Findings were adjusted for age, sex, baseline year, follow-up time, educational level, BMI, smoking, diabetes, systolic blood pressure, cholesterol, and physical activity.

Over a mean follow-up of 25.4 years, 7,935 participants received a diagnosis of dementia. The competing risk of death was more common, occurring in 19,647 people.

In a Poisson cause-specific model, exhaustion was linked with subsequent all-cause dementia (incidence rate ratio [IRR] 1.17, 95% CI 1.08-1.26), as was stress (IRR 1.24, 95% CI 1.11-1.38). These relationships remained significant in sensitivity analyses.

A subdistribution hazard model that estimated the effect on cumulative incidence also showed exhaustion (HR 1.08, 95% CI 1.01-1.17) and stress (HR 1.12, 95% CI 1.00-1.25) were linked with dementia risk over time. In contrast, depressive mood (HR 1.08, 95% CI 0.98-1.20) did not show a statistically significant association.

The study of psychological distress and brain health is "far from being incisive," noted Yoram Barak, MD, MHA, psychiatrist of the University of Otago in Dunedin, New Zealand, in an .

This "sophisticated analysis" adds "an important facet to the field by accounting for competing risk of death," Barak observed. "This should become a standard when researching these questions."

But relying on survey questions about experiences in the previous month may negate the possibility of understanding how stress may be a causative agent in dementia, since no information about lifelong traits or clinically diagnosed anxiety or depression was collected, Barak pointed out.

"We need to advance the field farther by creatively studying lifelong patterns of emotional states and relationships," he wrote. "Life trajectories of individuals and couples will teach us more about stress, distress, tensity, neuroticism, and dementia."

While the study questions on psychological distress do not form a validated multi-item questionnaire, the one-item measures for different symptoms of psychological distress correlate significantly, Sulkava and colleagues noted.

The research had other limitations, they acknowledged. Data about traumatic brain injury, hearing impairment, and low social contact -- three known dementia risk factors -- were not available. In addition, participants with missing covariate information had more risk factors for dementia or mortality.

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