Chronic heavy drinking is the most important and biggest preventable risk factor for every type of dementia, especially early-onset dementia, a new Canadian study has found.
The observational study by Centre for Addiction and Mental Health (CAMH) looked at 57,000 cases of early-onset dementia (before the age of 65). What they found was the 57 per cent of these cases were related to chronic heavy drinking.
“What was the most surprising was the level of association between heavy alcohol use and all types of dementia,” says study co-author Dr. Jurgen Rehm. “Before our study … alcohol was not even listed among the most important risk factors for dementia. We know this was wrong, but that it turned out to be the most important risk factor for all kinds of dementia in controlled analyses [and] it was surprising.”
According to the World Health Organization (WHO), chronic heavy drinking includes consuming more than 60 grams of pure alcohol on average per day for men (averaging out to four to five Canadian standard drinks) and 40 grams for women (about three standard drinks).
The study looked specifically at the effect of alcohol-use disorders, and included people who had been diagnosed with mental and behavioural disorders or chronic disease that were linked to chronic alcohol drinking.
While researchers weren’t able to determine why alcohol was the top risk factor, they were able to identify two major pathways as to why that may be.
“Heavy drinking is linked to structural and functional changes in the brain which can be identified via imaging,” Rehm explains. “These changes actually start already at moderate drinking, but there is a dose-response relationship, and heavy drinking is much more important for worsening cognitive functioning.”
Rehm says there are also indirect ways how alcohol impacts on dementia through other risk factors. For example, alcohol use increases the risk for hypertension, and it leads to liver damage, among other things.
Rehm and his team also found that there was a gender divide in the results. While the majority of dementia patients were women, almost two-third of all early-onset dementia patients were men (about 65 per cent).
According to the findings, alcohol use disorders were also associated with all other independent risk factors for dementia onset. They include tobacco smoking, high blood pressure, diabetes, lower education, depression and hearing loss – all of which are identified as “modifiable risk factors.”
“Dementia is one of the quickest increasing and most disabling disease clusters currently, and very important for public health,” Rehm says. “Many efforts are being started now to look into potential ways of prevention, and reduction of alcohol consumption is now a promising way to reduce incidence of dementia, or to postpone the onset.”
Non-modifiable risk factors for dementia include age, a family history and genetics and other medical conditions like Parkinson’s disease, multiple sclerosis, chronic kidney disease and HIV, the Alzheimer’s Society of Canada says.
As of 2016, it is estimated that about 564,000 Canadians live with dementia, and about 25,000 new cases are diagnosed every year. By 2031, that number is expected to jump to 937,000 – an increase of 66 per cent, the Alzheimer Society of Canada reports.