The researchers defined heavy drinking in men as consuming 36 g of alcohol or more per day. This is the amount of alcohol in four to five 25 ml measures of spirits, or around two pints of beer, or two 175 ml glasses of wine, depending on strength.
Lead author Dr. Séverine Sabia, of the department of epidemiology and public health at University College, says:
"Much of the research evidence about drinking and a relationship to memory and executive function is based on older populations. Our study focused on middle-aged participants and suggests that heavy drinking is associated with faster decline in all areas of cognitive function in men."
Published recently online in the journal Neurology, the study drew on data from over 5,000 men and 2,000 women who took part in the Whitehall II study of UK civil servants. The participants were aged between 44 and 69 when they joined the study between 1997 and 1999.
Their drinking habits, memory and executive functions were assessed at the start of the study and then twice more over a 10-year follow-up.
Tests of executive function measure certain thinking skills, such as reasoning, attention, and problem-solving.
The results showed there were no differences in memory and executive function decline among men who were light or moderate drinkers (under 20 g of alcohol a day).
But men who were heavy drinkers (36 g or more of alcohol per day) experienced memory and executive function decline that was between 1.5 and 6 years faster than counterparts who were not heavy drinkers.
The study did not find the same was true of women, although this could be because there were not enough heavy drinkers among the female participants.
Dr. Simon Ridley, head of research at leading UK charity Alzheimer's Research UK, says:
"Observational studies such as this can be important for identifying factors that may influence the risk of memory decline or disease, but it's difficult to pinpoint cause and effect with this type of research."
He explains that while the people in the study did not have dementia, memory decline can be a precursor to the disease, and we need to know more about the risk factors for this decline so we can prevent it.
He underlines the importance of continuing to invest in research so we can find out how best to keep our brains healthy as we age and prevent diseases that cause dementia, and adds:
"In the meantime, the best evidence suggests that in addition to not drinking to excess we can lower the risk of dementia by eating a healthy, balanced diet, keeping an eye on our blood pressure and weight, and taking regular exercise."
Funds from the British Medical Research Council, British Heart Foundation, the US National Heart, Lung, and Blood Institute and the US National Institute on Aging helped finance the study.
In another study published recently, researchers in Canada found that drinking alcohol can impair vision by up to 30% before we even hit the legal limit.
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