People who have sworn off alcohol for decades or longer run a higher risk of dementia late in life than moderate drinkers, according to a study published Wednesday.
Long-term teetotallers were roughly 50 percent more likely to suffer Alzheimers or another form of neurodegenerative disease, scientists reported in the BMJ, a medical journal.
With heavy drinking, however, dementia became even more prevalent, though for different reasons.
Unlike earlier research, the study did not find a link between abstinence and a shorter life expectancy, as compared to occasional drinkers.
The results were based on a review of medical records rather than the more scientifically rigorous clinical trials used to assess new drugs, and the number of cases examined was relatively small.
But the startling results are robust, and should prompt government-funded trials to assess "the possible protective effect of light-to-moderate alcohol use on risk of dementia," commented Sevil Yasar, an associate professor at the John Hopkins School of Medicine who was not involved in the study.
Worldwide, about seven percent of people over 65 suffer from some form of dementia, a percentage that rises to 40 percent above the age of 85. The number of sufferers is expected to triple by 2050.
The research, led by Severine Sabia at the French National Institute of Health and Medical Research, also found that, among moderate drinkers, wine consumption correlated with a lower risk of dementia than beer or spirits, such as whiskey, gin or vodka.
"Light-to-moderate" drinking was defined, during middle age, as one-to-14 drinks per week, corresponding to the maximum limit recommended for both men and women in Britain.
The 14-drink-per-week maximum, similar to guidelines in other countries, is the equivalent of six medium (175-millilitre) glasses wine at 13 percent alcohol, six pints of four-percent beer, or 14 25-ml shots of 40-degree spirits.
The study was not set up to explain why non-drinkers might be more prone to cognitive decline, but the findings offered possible clues.
- Alcohol carries other risks -
"Some of the excess risk of dementia in abstainers was explained by great risk of cardiometric disease," such as stroke, coronary hear disease and diabetes, Sabia and her team concluded.
Non-drinkers canvassed were more likely to be burdened with lifestyle diseases, but the link with dementia held true even after these health problems were taken into account, they reported.
In the case of wine, earlier studies have suggested that so-called polyphenolic compounds may offer some protection to neural networks and blood vessels, but such findings remain controversial.
The findings are based on health records, part of the Whitehall II study on long-term health, for more than 9,000 British civil servants who were 35 to 55 years old in 1985.
Alcohol intake of participants was monitored regularly for two decades, and hospital records were examined for signs of heart and alcohol-related disease.
A total of nearly 400 dementia cases, with onset occurring, on average, at age 76, were reported.
The study also confirmed that heavy drinking is strongly linked to dementia, with a 17-percent increase in risk for each addition seven drinks per week.
Chronic heavy drinking is a major risk factor for all types of dementia, especially early onset of the disease, research published earlier this year found.
The World Health Organisation (WHO) defines "chronic heavy drinking" as more than 60 grammes of pure alcohol, six or more standard drinks, a day for men, and in excess of 40 grammes per day for women.
The new 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," the study cautioned.
"One-to-14 units a week may benefit brain health," said Yasar. "However, alcohol choices must take into account all associated risks, including liver disease and cancer."