A new study in the United States has found that older people who drink moderate amounts of alcohol may have a lower risk of dementia.

People who consumed between eight and 14 alcoholic drinks a week had a 37% lower risk of the disease than the general population, the International Conference on Alzheimer’s Disease heard.

More than 14 drinks a week led to a risk of developing dementia that was twice the norm, however.

The researchers at Wake Forest University focused on 3,069 people aged 75 or older.

Taking into account factors such as smoking, depression and social activity, researchers began the six-year study with 2,587 participants who had no signs of problems with their brain while 482 had mild cognitive impairment. During the study 523 new dementia cases emerged.

The researchers found that one or two drinks a day was associated with a 37% lower risk of dementia among those who were cognitively normal at the start of the study.

But alcohol intake was associated with faster cognitive decline among those who already had mild cognitive impairment.

Among the people in the study, four in ten did not drink alcohol, four in ten consumed up to seven drinks a week, one in ten consumed 8-14 drinks a week, and one in ten consumed more than 14 drinks a week.

Lead researcher Kaycee Sink said it was not yet clear why a moderate amount of alcohol seemed to be good for the brain, but that there were several possible ways in which moderate drinking might be associated with reduced risk of dementia.

One was a possible beneficial effect on HDL cholesterol and blocking platelets, which also leads to a reduced heart disease risk.

Animal studies have also shown that low amounts of alcohol stimulate the release of acetylcholine, a chemical in the brain that is important in memory, Sink said.

But experts warned against recommending that older adults start drinking alcohol based on this study when they had never drunk before.

Those who were already light to moderate drinkers might, however, be at a lower risk of developing Alzheimer’s disease or other dementias.

But alcohol might accelerate memory loss in people in which the process had already begun.

Alzheimer’s Research Trust chief executive Rebecca Wood warned that exceeding one to two drinks per day on a regular basis could double the risk of developing dementia.

Wood said that on the basis of this study, older people with memory problems should consider not drinking at all.

She added that the best way to reduce dementia risk was still to eat a balanced diet, exercise regularly and remain socially active.

The results conflict with those from a small study published in Neurology in 2007, which suggests people with mild cognitive impairment might slow their mental decline with up to one drink a day.