Fifteen studies examined more than 28,000 people for from two to eight years and controlled for other variables, including age, sex, smoking. Light to moderate drinking ranged from 1 to 28 drinks per week. But specificity regarding type and number of drinks could not be ascertained.
Exactly why does alcohol consumption work this way? There is ample evidence from other studies that moderate alcohol consumption can increase HDL, or "good cholesterol," improve blood flow to the brain and decrease blood coagulation. The general medical view is that anything reducing cardiac and cardiovascular disease would also help prevent cognitive impairment and dementia. Some experiments show that ethanol encourages the release of a brain chemical that could be responsible for improved memory. Another view is that anti-oxidants in wine might also boost cognitive performance. Also, other lifestyle factors, not explicitly accounted for, may reduce the risk for dementia.
One study reported in 2007 of Italians found that over 3.5 years, those with mild cognitive impairment who drank less than seven drinks a week progressed to dementia at a rate 85 percent slower than those who drank nothing.
In 2005, researchers at Harvard School of Public Health and Brigham and Women's Hospital reported an analysis of data from 12,480 women age 70 to 81 who participated in the Nurses' Health Study beginning in 1980. The study was twice as large as any earlier study and also investigated the effects of different forms of alcohol on cognition and memory. Women who consume alcohol moderately on a daily basis are about 20 percent less likely than abstainers to experience poor memory and decreased thinking abilities, according to the research. The senior author of the study explained that "Women who consistently were drinking about one-half to one drink per day had both less cognitive impairment as well as less decline in their cognitive function compared to women who didn't drink at all." It didn't matter whether the women drank beer, wine, or liquor (distilled spirits). The positive effects of the alcoholic beverages were all the same.
Another study examined over 400 people who were at least 75 years old and tracked their health for a period of six years. Researchers found that drinkers were only half as likely to develop dementia as similarly-aged abstainers from alcohol. Abstainers were defined as people who consumed less than one drink of alcohol per week.
A 2003 study in the Journal of the American Medical Association (JAMA) reported that moderate drinking could reduce the risk for dementia. It found that moderate drinkers have a 54 percent lower chance of developing dementia than abstainers. About 6,000 people age 65 and older in four communities across the provided detailed information about their eating and drinking patterns. Researchers compared the drinking behaviors of the people who developed dementia with people who didn't. While moderate drinking dramatically reduced the risk for dementia, heavy or abusive drinking increased it somewhat. The type of alcohol beverage consumed (wine, spirits, or beer) didn't make a difference in the protective effects of drinking in moderation.
Despite uncertainties inherent in all such scientific pursuits, there is a reasonable basis for adopting this view: "Booze boosts the brain: A drink a day keeps dementia away." When you stop remembering this you won't know you're in trouble.