Light to moderate alcohol consumption has generally been considered to have some health benefits, including possibly reducing risk of cognitive decline.
However, two studies reported today at the Alzheimer's Association International Conference in Vancouver suggest that moderate alcohol use in late-life, heavier use earlier in life, and 'binge' drinking in late-life increase risk of cognitive decline.
They measured frequency of current and past alcohol use at the beginning, mid-point (years 6 and 8) and late phases (years 10 and 16) of the study. The researchers assessed participants at the end of the study for mild cognitive impairment and dementia.
At baseline, 40.6% were non-drinkers, 50.4% were light drinkers (0 to 7 drinks/week), and 9.0% were moderate drinkers (7 to 14 drinks/week). Heavy drinkers (14 drinks/week) were excluded.
The research discovered that women who reported drinking more in the past than at the beginning of the study were at 30% increased risk of developing cognitive impairment.
Moderate drinkers at baseline or at mid-point had similar risk of cognitive impairment to non-drinkers; however, moderate drinkers in the late phase of the study were roughly 60% more likely to develop cognitive impairment.
However, in contrast, women who changed from non-drinking to drinking over the course of the study had a 200% increased risk of cognitive impairment.
"We found that heavier use earlier in life, moderate use in late-life, and transitioning to drinking in late-life were associated with an increased risk of developing cognitive impairment.
"These findings suggest that alcohol use in late-life may not be beneficial for cognitive function in older women," explains lead researcher, Tina Hoang.
"It may be that the brains of oldest old adults are more vulnerable to the effects of alcohol, but it is also possible that factors associated with changing alcohol use related to coping or loss could be involved.
"Clinicians should carefully assess their older patients for both how much they drink and any changes in patterns of alcohol use," Hoang added.
Alcohol - friend or foe? You decide...
Commenting on the research, a spokesperson from the Alzheimer's Society said in a statement: "There has been a lot of research into the link between alcohol and dementia. What is becoming increasingly apparent is that while an occasional tipple could actually help to protect the brain, binge drinking could be linked to an increased cognitive decline.
"These latest studies help reinforce the link between heavy drinking and dementia, but we need much more research to better understand exactly how drinking alcohol affects the brain. In the meantime, eating well and exercising regularly are key ways of reducing your risk of dementia."
Little is known about the cognitive effects of heavy episodic (or 'binge') drinking in older people. Binge drinking is a pattern of alcohol consumption in which someone who is not otherwise a heavy drinker consumes several drinks on one occasion.
"We know that binge drinking can be harmful," Dr. Iain Lang from the Peninsula College of Medicine and Dentistry, University of Exeter said in a statement.
"For example, it can increase the risk of harm to the cardiovascular system, including the chance of developing heart disease, and it is related to increased risk of both intentional and unintentional injuries."