What they found was the 57 per cent of these cases were related to chronic heavy drinking.
But there is also agreement that more research is needed to work out the role played by the volume of alcohol consumed against how often alcohol is drunk - and how this affects the risk of early-onset dementia.
Image for representational purposes only.
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).
According to the World Health Organisation (WHO), "heavy drinking" is defined as consuming more than 60 grams of pure alcohol a day for men and more than 40 grams per day for women.
Research shows that heavy drinking can increase the risk of developing dementia.
Women are more likely than men to be diagnosed with dementia, but men made up almost two thirds of patients diagnosed with early-onset dementia.
The authors also mentioned that on average, alcohol use disorders could reduce life expectancy by about 20 years, and dementia among the prominent causes of death for these people.
Researchers studied a French national database to examine the effect of alcohol disorders, including those diagnosed with mental and behavioural conditions or chronic disease attributable to drink abuse.
The NHS estimates that just under one in 10 men in the United Kingdom and one in 20 women show signs of alcohol dependence. It suggests that alcohol use disorders may contribute in many ways to the risk of dementia.
However, there is a big difference between low-to-moderate drinking and people who drink in a way that is harmful - those who are binge-drinkers or alcohol-dependent. "Alcohol use disorders also increase the risk of high blood pressure, diabetes, stroke, atrial fibrillation, and heart failure, which may in turn increase the risk of vascular dementia".
"Heavy drinking is linked to structural and functional changes in the brain which can be identified via imaging", Rehm explains.
The authors say their study adds to the mounting evidence that excessive alcohol poses serious health risks, and that many people drink regularly at levels that are hazardous to their physical and mental health. They excluded those at risk of developing rare forms of dementia, such as those brought on by infectious diseases like HIV or other neurological disorders. In men, the risk was increased by a factor of 4.7, while in women, it increased by a factor of 4.3. "Alcohol use disorders are probably associated with poor diet and lifestyle, smoking, cardiovascular comorbidity, lower adherence to medical treatments, depression, and potentially social isolation", they wrote.
More than 80% of French adults older than age 65 - and 50% before that age - were admitted to hospitals over the 6-year study period, which supports a high generalizability of this research, Schwarzinger's group noted. But the latest study emphasizes that escalating to heavy drinking habits can have detrimental consequences.
Chronic heavy drinking is more than four drinks a day for a man, and more than three for a woman.