MAYWOOD, Ill. -- Moderate social drinking significantly reduces the risk of dementia and cognitive impairment, according to an analysis of 143 studies by Loyola University Chicago Stritch School of Medicine researchers.
Researchers reviewed studies dating to 1977 that included more than 365,000 participants. Moderate drinkers were 23 percent less likely to develop cognitive impairment or Alzheimer's disease and other forms of dementia.
Wine was more beneficial than beer or spirits. But this finding was based on a relatively small number of studies, because most papers did not distinguish among different types of alcohol.
Results are reported in the journal Neuropsychiatric Disease and Treatment. The authors are Edward J. Neafsey, Ph.D., and Michael A. Collins, Ph.D., professors in the Department of Molecular Pharmacology and Therapeutics.
Heavy drinking (more than three to five drinks per day) was associated with a higher risk of cognitive impairment and dementia, but this finding was not statistically significant.
"We don't recommend that nondrinkers start drinking," Neafsey said. "But moderate drinking -- if it is truly moderate -- can be beneficial." Moderate drinking is defined as a maximum of two drinks per day for men and 1 drink per day for women.
Among the studies reviewed, 74 papers calculated the ratios of risk between drinkers and nondrinkers, while 69 papers simply stated whether cognition in drinkers was better, the same or worse than cognition in nondrinkers. Neafsey and Collins did a meta-analysis of the studies that calculated risk ratios and found that moderate drinkers were 23 percent less likely to develop dementia or cognitive decline.
-- The protective effect of moderate drinking held up after adjusting for age, education, sex and smoking.
-- There was no difference in the effects of alcohol on men and women.
-- The beneficial effect of moderate drinking was seen in 14 of 19 countries, including the United States. In three of the remaining five countries, researchers also found a benefit, but it was not strong enough to be statistically significant.
-- The findings were similar across different types of studies (longitudinal cohort studies, case-control studies and cross-sectional studies).
It is unknown why moderate drinking can have a beneficial effect. One theory suggests that the well-known cardiovascular benefits of moderate alcohol consumption, such as raising good HDL cholesterol, also can improve blood flow in the brain and thus brain metabolism.
A second possible explanation involves "sick quitters." According to this theory, nondrinkers have a higher risk of cognitive impairment and dementia because the group includes former heavy drinkers who damaged their brain cells before quitting. But the analysis by Neafsey and Collins did not support this explanation. They found that in studies that excluded former heavy drinkers, the protective effect of moderate drinking still held up.
Neafsey and Collins suggest a third possible explanation: Small amounts of alcohol might, in effect, make brain cells more fit. Alcohol in moderate amounts stresses cells and thus toughens them up to cope with major stresses down the road that could cause dementia.
For people who drink responsibly and in moderation, there's probably no reason to quit. But because of the potential for alcohol to be abused, Neafsey and Collins do not recommend that abstainers begin drinking.
The researchers note that there are other things besides moderate drinking that can reduce the risk of dementia, including exercise, education and a Mediterranean diet high in fruits, vegetables, cereals, beans, nuts and seeds. Even gardening has been shown to reduce the risk of dementia.
Moreover, there are times when people should never drink, including adolescence, pregnancy and before driving, the researchers said.
The Neafsey and Collins study was supported by the National Institutes of Health.
Loyola University Health System (LUHS) is a member of Trinity Health. Based in the western suburbs of Chicago, LUHS is a quaternary care system with a 61-acre main medical center campus, the 36-acre Gottlieb Memorial Hospital campus and more than 30 primary and specialty care facilities in Cook, Will and DuPage counties. The medical center campus is conveniently located in Maywood, 13 miles west of the Chicago Loop and 8 miles east of Oak Brook, Ill. The heart of the medical center campus, Loyola University Hospital, is a 569-licensed-bed facility. It houses a Level 1 Trauma Center, a Burn Center and the Ronald McDonald® Children’s Hospital of Loyola University Medical Center. Also on campus are the Cardinal Bernardin Cancer Center, Loyola Outpatient Center, Center for Heart & Vascular Medicine and Loyola Oral Health Center as well as the LUC Stritch School of Medicine, the LUC Marcella Niehoff School of Nursing and the Loyola Center for Fitness. Loyola's Gottlieb campus in Melrose Park includes the 264-licensed-bed community hospital, the Professional Office Building housing 150 private practice clinics, the Adult Day Care, the Gottlieb Center for Fitness, Loyola Center for Metabolic Surgery and Bariatric Care and the Loyola Cancer Care & Research at the Marjorie G. Weinberg Cancer Center at Melrose Park.