By Rita Buckley
NEW YORK—Older women with reduced visual contrast sensitivity are at increased risk of developing mild cognitive impairment or dementia, according to a new study.
The association has been found before in cross-sectional research, but until now had not been studied prospectively, according to Dr. Kristine Yaffe of the University of California, San Francisco, and colleagues.
The team conducted a prospective, community-based study on a subsample of aging women from the Study of Osteoporotic Fractures, a longitudinal multicenter trial that examined predictors of falls and fractures.
A total of 1,352 community-dwelling women, most of them white, from three sites were tested for contrast sensitivity, a functional measure of low-contrast vision. The patients' mean age at baseline was 77.7 years.
On a scale of 0 (worst) to 150 (best), mean contrast sensitivity in the cohort was 32.9.
Ten years from baseline, 536 (39.6%) of the women had developed mild cognitive impairment/dementia. Women with lower baseline contrast sensitivity had an increased risk of mild cognitive impairment/dementia (p<0.0001 for linear trend).
For those in the lowest quartile of contrast sensitivity, the odds of developing mild cognitive impairment/dementia was 2.16 times those for women in the highest quartile.
Every 10-point decrease in contrast sensitivity was associated with a 21% increase in the odds of developing mild cognitive impairment/dementia (adjusted OR, 1.5).
Additional adjustments for depression score, alcohol use, diabetes, hypertension and baseline cognitive score led to similar results (OR, 1.15).
"This research is important," Dr. Yaffe told Reuters Health by email. "It's the only study to prospectively investigate how poor visual contrast is associated with higher risk of developing dementia and mild cognitive impairment after 10 years of follow-up."
The key take-home message, she said, is that visual dysfunction or visual system degeneration may be a risk factor or early marker for dementia.
Dr. Tinatin Chabrashvili, director of the Dementia Clinic at Tufts Medical Center in Boston, told Reuters Health the findings suggests that visual-system involvement occurs in parallel or precedes dementia-related neurodegeneration.
Dr. Chabrashvili, who was not involved in the study, cautioned that it was unable to distinguish between types of dementias and also pointed out the lack of diversity in the study sample.
Still, she said, "The findings may help us identify individuals at risk of developing dementia in as early as 10 years," adding, "This will be especially important when we have neuroprotective therapies."
The study was funded by grants from the National Institute of Aging. Dr. Yaffe and colleagues reported no conflicts of interest.
Ann Neurol 2018.
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