"In our study, older women who drank moderate amounts of alcohol tended to perform better on tests for cognitive function and dementia," said Mark Espeland, Ph.D., lead researcher. "Most of these women drank one or two drinks per day."
The researchers used data from the Women's Health Initiative Memory Study, a large national study to assess the effects of hormone therapy on dementia and cognitive function. As part of the study, women reported how much alcohol they drank daily.
The research, which will be reported in the February 1 issue (Vol. 161, pages 228-38) of the American Journal of Epidemiology, found that women who reported having one or more alcohol drinks daily scored higher on tests of cognitive function than women who reported drinking less. Cognitive function includes concentration, language, memory and abstract reasoning.
"Women who reported drinking one or more drinks a day had a 40 percent lower risk of significant declines in cognitive function over time, compared to women who reported no alcohol intake," said Espeland, a professor of public health sciences.
The researchers followed 4,461 women aged 65 to 79 years for an average of 4.2 years with annual Modified Mini-Mental State Examinations (MMSE), which is a measure of cognitive function, and other tests to detect mild cognitive impairment and probable dementia. Dementia occurs when memory, judgment and thinking ability decline substantially to the point of interfering with basic day-to-day activities.
"There are a number of reasons one might expect moderate alcohol intake to be beneficial," Espeland says. "Some cognitive problems are due to strokes and blood vessels in the brain becoming blocked, and alcohol may reduce the development of blood clots and increase blood flow, thereby improving cognition."
Espeland said alcohol also tends to increase levels of high-density lipoprotein, or "good" cholesterol, which might also reduce the risk for narrowed vessels in the brain. In addition, alcohol may decrease the formation of plaque that is associated with Alzheimer's disease.
Previous studies have also indicated that moderate levels of alcohol intake reduce the risk of dementia and decline in cognitive function. Espeland said, however, that the results must be interpreted with caution.
"While evidence is growing that alcohol is beneficial in this area, it is still unclear whether alcohol intake or another defining characteristic is the reason for reduced risk," he said.
The researchers adjusted for other factors that might affect the results, such as education level and family income, and still found the same pattern of moderate alcohol intake associated with better cognitive function and less risk of dementia.
"But we cannot rule out that unmeasured factors affected cognition," he said. "My sense is that for older women who choose to drink - and are not restricted from drinking for medical reasons - moderate alcohol intake is not harmful for cognition and may provide some benefits by reducing the risk of cognitive decline.
"Until we better understand the reasons why alcohol consumption is associated with better cognitive functioning, however, these results on their own are not a reason for people who don't drink to start or for those who drink less to increase their intake."
Espeland's co-researchers were Lin Gu, M.S., Laura Coker, Ph.D., and Stephen R. Rapp, Ph.D., also from Wake Forest Baptist, Kamal H. Masaki, M.D., from the University of Hawaii, Robert D. Langer, M.D., M.P.H., from the University of California at San Diego School of Medicine, Marcia L. Stefanick, Ph.D., from Stanford University School of Medicine, and Judith Ockene, Ph.D., from the University of Massachusetts.
About Wake Forest University Baptist
Medical Center: Wake Forest Baptist is an academic health system comprised of North Carolina Baptist Hospital and Wake Forest University Health Sciences, which operates the university's School of Medicine. The system comprises 1,282 acute care, psychiatric, rehabilitation and long-term care beds and is consistently ranked as one of "America's Best Hospitals" by U.S. News & World Report.