People who either abstain from drinking from alcohol in the long term or drink heavily are at increased risk of developing dementia compared to moderate drinkers, a study suggests.
Researchers found that both those who abstained from alcohol or consumed more than 14 units a week – the UK recommended maximum limit for both men and women – during middle age were at higher risk of dementia.
The findings, by researchers from the French National Institute of Health and Medical Research and University College London, are published in the British Medical Journal today.
They noted that older studies had indicated that moderate drinking reduced dementia risk, while abstinence and heavy drinking increased it, but said the previous evidence was far from conclusive.
Their latest findings are based on 9,087 British civil servants aged between 35 and 55 in 1985 who were taking part in the long-term Whitehall II Study.
Participants were assessed at regular intervals between 1985 and 1993 – when the average age among the group was 50 – on their alcohol consumption and alcohol dependence. Admissions for alcohol related chronic diseases and cases of dementia were identified from hospital records.
Of the 9,087 participants, 397 cases of dementia were recorded over an average follow-up period of 23 years. The average age at dementia diagnosis was 76 years.
“While this study does throw up questions about alcohol and dementia, there could be other risk factors at play”
The researchers found that abstinence in midlife or drinking more than 14 units a week was associated with a higher risk of dementia, compared with drinking one to 14 units of alcohol a week.
Long-term abstainers, those decreasing their consumption and long-term consumers of more than 14 units a week were all at a higher risk compared with long-term drinkers of one to 14 units.
Among those drinking above 14 units a week of alcohol, every seven unit a week increase in consumption was associated with 17% increase in dementia risk.
In addition, a history of hospital admission for alcohol related chronic diseases was associated with a four times higher risk of dementia.
In abstainers, the researchers showed that some of the excess dementia risk was due to a greater risk of cardiometabolic disease – including stroke, coronary heart disease, and diabetes.
The researchers noted that the underlying mechanisms were likely to be different for why abstainers and those consuming over 14 units a week were at higher risk of dementia.
They said their findings “strengthen the evidence that excessive alcohol consumption is a risk factor for dementia”.
The study results should also “encourage use of lower thresholds of alcohol consumption in guidelines to promote cognitive health at older ages”, said the researchers.
However, they also highlighted that their findings “should not motivate people who do not drink to start drinking given the known detrimental effects of alcohol consumption for mortality, neuropsychiatric disorders, cirrhosis of the liver, and cancer”.
Dr Doug Brown
Dr Doug Brown, chief policy and research officer at Alzheimer’s Society, said: “This study supports other work that continues to question whether drinking up to the equivalent of six glasses of wine per week might have a protective effect against dementia.
“However, as this is an observational study we need longer trials to explore whether this is actually the case – particularly as we know people tend to underestimate their alcohol consumption,” he said.
“While this study does throw up questions about alcohol and dementia, there could be other risk factors at play. What we do know is that excessive drinking is a proven cause of liver disease and cancers,” he added.