Chronic heavy drinkers may have an increased risk of developing dementia, particularly early-onset dementia, a new study involving over one million adults has found.

French researchers set out to investigate the impact of alcohol use disorder on cognitive health. Alcohol use disorder, also referred to as alcoholism, describes a pattern of drinking which has become uncontrolled and problematic.

Symptoms can include continuing to drink even though it has having an adverse effect on family, friends and/or work, experiencing cravings for alcohol, having to drink more to get the effect you want and suffering withdrawal symptoms when not drinking.

Chronic heavy drinking is defined by the World Health Organization as consuming more than 60g of pure alcohol per day for men (around six or more standard drinks), and more than 40g per day for women (around four or more standard drinks).

The researchers looked at over 1.1 million adults who had been diagnosed with dementia between 2008 and 2013. Of these, around 5% (over 57,000 people) had been diagnosed with early-onset dementia - that is dementia before the age of 65.

The study found an increased risk of dementia among chronic heavy drinkers overall, but this risk was particularly strong when it came to early-onset dementia, with 39% of cases attributable to alcohol-related brain damage, and 18% related to other alcohol use disorders.

Overall, alcohol use disorders were linked with a three times greater risk of all types of dementia and were the strongest modifiable risk factor for dementia onset.

"Our findings suggest that the burden of dementia attributable to alcohol use disorders is much larger than previously thought, suggesting that heavy drinking should be recognised as a major risk factor for all types of dementia.

"A variety of measures are needed such as reducing availability, increasing taxation, and banning advertising and marketing of alcohol, alongside early detection and treatment of alcohol use disorders," commented the study's lead author, Dr Michaël Schwarzinger, of the Translational Health Economics Network in France.

He said that this area needs more research but suggested that the link between heavy alcohol use and dementia is ‘likely a result of alcohol leading to permanent structural and functional brain damage'.

"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. Lastly, heavy drinking is associated with tobacco smoking, depression, and low educational attainment, which are also risk factors for dementia," Dr Schwarzinger noted.

Details of these findings are published in the journal, The Lancet Public Health. In a linked comment, Prof Clive Ballard of the University of Exeter Medical School in the UK, said that this study is ‘immensely important'.

"It highlights the potential of alcohol use disorders, and possibly alcohol consumption, as modifiable risk factors for dementia prevention...In our view, this evidence is robust and we should move forward with clear public health messages about the relationship between both alcohol use disorders and alcohol consumption, respectively, and dementia," he said.