Alcohol said to affect onset of dementia

Adults over age 65 who consume between one and six alcoholic beverages each week have a lower risk of dementia than either nondrinkers or heavier drinkers, according to findings that appear in the March 19 issue of the Journal of the American Medical Association (JAMA).

“We found that abstainers had odds of [suffering from] dementia that were about twice as high as the odds of ‘moderate drinkers,’” explains the study’s lead author, Kenneth Mukamal of the Division of General Medicine and Primary Care at Beth Israel Deaconess Medical Center (BIDMC). “Furthermore, those who drank 14 or more drinks per week also had a higher risk of dementia than the moderate drinkers.”

The case control study compared the alcohol consumption patterns of 373 dementia patients with 373 control subjects who did not have dementia. The study subjects included both men and women who were screened from among 5,888 older adults participating in the Cardiovascular Health Study (CHS), a large cohort study sponsored by the National Heart, Lung and Blood Institute. The CHS began nearly 15 years ago to assess a variety of medical conditions among individuals over age 65 in four communities in Pennsylvania, Maryland, North Carolina, and California.

According to Mukamal, who is also assistant professor of medicine at Harvard Medical School, dementia was most commonly caused by either Alzheimer’s disease or vascular dementia (as might develop following a series of strokes). Dementia patients were identified through a careful series of neurological and neuropsychiatric screening tests, including MRIs, between 1992 and 1999. Follow-up examinations were conducted each year.

Alcohol consumption was determined during participants’ yearly medical visits, at which time study subjects were asked to record the typical number of 12-ounce servings of beer, 6-ounce servings of wine, and shots of liquor they drank at a sitting, as well as the usual frequency with which they consumed these beverages. The investigators took the average of the participants’ reported alcohol use from the beginning of the CHS study in 1988-89 as well as at the time of their MRI testing in 1992-94.

After adjusting for numerous factors – including age, sex, race, apoE4 status (a genetic risk factor for dementia), educational attainment, income, marital status, estrogen replacement therapy, current and former cigarette smoking, diabetes, body mass index, physical activity, total cholesterol, atrial fibrillation, history of congestive heart failure, and stroke – the results showed a clear association between moderate alcohol consumption and reduced risk of dementia.

“The results demonstrated a distinct ‘U-shaped relationship,’” says Mukamal. On one side of the U-curve, he explains, were the abstainers, whose odds ratios for developing dementia were 1.00. On the opposite side of the U were those individuals who consumed 14 or more drinks per week, whose odds ratios were found to be 1.22. And, in the middle, the curve was represented by the moderate drinkers (one to six drinks per week), whose odds ratios for dementia were 0.46.

“Percentage-wise, this means that the moderate drinkers have a 54 percent lower risk of dementia than the abstainers, while the heavier drinkers have a 22 percent higher risk of dementia than the abstainers,” adds Mukamal.

Heavier drinking was particularly linked to dementia among men – for whom the odds of dementia were doubled – and among participants who were positive for the apoE4 gene, for whom the risk of dementia was tripled.

One theory behind these findings is that alcohol may be protecting against dementia by guarding against the development of cerebral arteriosclerosis, or hardening of the arteries. Earlier work by Mukamal and colleagues found that light-to-moderate alcohol use was associated with a lower prevalence of white matter lesions in the brain and subclinical infarcts, neurological abnormalities that are believed to be related to blood-vessel functioning.

“There is a large body of literature concerning alcohol use and cognitive function, but to this point it hasn’t been clear whether alcohol consumption is good, bad, or neutral,” says Mukamal. “This study for the first time looks at clinically diagnosed dementia in a large population of older adults who have more than one measurement of alcohol use.”

However, he cautions, “given the observational nature of our study, we cannot recommend that older adults begin drinking moderately on the basis of these findings alone. Older adults should discuss their alcohol use with their physicians and make appropriate decisions based on these discussions.”