CHICAGO, June 11 -- Mild cognitive impairment is more likely to develop in those who are beset by chronic mental distress than those who worry the least, concluded researchers here.
That's the conclusion of researchers here, who found that people who scored high on a test of chronic mental distress were more than 40% more likely to develop mild cognitive impairment than those who were the most laid-back.
In an analysis of prospective data from two large studies of aging and the brain, the risk of developing mild cognitive impairment over a 12-year follow-up increased by about 2% for every one-point increase on a measure of chronic distress, according to Robert Wilson, Ph.D., of Rush University Medical Center here.
Depression, on the other hand - although known to predict cognitive impairment and dementia - appeared in this study to be merely a "proxy for the enduring tendency to experience negative emotions," Dr. Wilson and colleagues reported in the June 12 issue of Neurology.
Mild cognitive impairment - considered a transitional step to full-blown dementia - implies mild memory or cognitive problems, but no significant disability, the researchers said.
"These findings suggest that, over a lifetime, chronic experience of stress affects the area of the brain that governs stress response," Dr. Wilson said. "Unfortunately, that part of the brain also regulates memory."
The findings come from data collected for the Religious Orders Study and the Rush Memory and Aging Project, two longitudinal cohorts. Volunteers (mean age of 76.8) had no dementia or mild cognitive impairment at baseline.
They completed a range of baseline tests, including the Mini-Mental State Examination, the Center Epidemiologic Studies Depression scale and the NEO Five-Factor Inventory, which is used as a measure of proneness to psychological distress. They also underwent yearly clinical examinations.
On the NEO test, volunteers rated their agreement to such statements as: "I am not a worrier"; "I often feel tense and jittery"; and "I often get angry at the way people treat me." Scores could range from 0 to 44, with a higher score indicating a higher level of chronic distress.
The study found:
Over the 12 years, 482 of the 1,256 volunteers developed mild cognitive impairment.
The mean distress score at baseline was 15.6, and was not correlated with age, sex, or education, but was significantly associated at P<0.001) with depressive symptoms.
In a simple proportional hazards model, each one-point increase in distress score was associated with 2% increase in risk of mild cognitive impairment. The hazard ratio was 1.02, with a 95% confidence interval from 1.01 to 1.04.
Depressive symptoms were associated with increased risk, but the association became non-significant when the researchers controlled for distress score. The hazard ratio associated with depressive symptoms became 1.02, with a 95% confidence interval from 0.96 to 1.09.
The bottom line, Dr. Wilson and colleagues said, is that a person with a high distress score of 24 would be 42% more likely to develop mild cognitive impairment than a person with a low score of eight.
"People differ in how they tend to experience and deal with negative emotions and psychological distress, and the way people respond tends to stay the same throughout their adult lives," Dr. Wilson said.
Because of that and other considerations, the researchers said, it's unlikely that a high distress score is simply a sign of encroaching disease. Instead, they said, it's probably a risk factor - although exactly how distress increases risk remains to be understood.
An unexpected finding is that that the association of distress with risk of impairment was higher in men than in women, although the sexes did not differ in the likelihood experiencing distress.
The research was supported by the National Institute on Aging and the Illinois Department of Public Health. The authors reported no conflicts of interest. Primary source: NeurologySource reference: Wilson RS et al. "Chronic distress and incidence of mild cognitive impairment." Neurology 2007;68:2085-92.
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