Researchers say drinking is the number one preventable risk for dementia. However, there’s conflicting research on how much alcohol is too much.

Alcohol and dementia may have a stronger connection than previously thought.

The majority of early onset dementia cases are associated with alcohol use disorders or are alcohol-related, according to research recently published in The Lancet Public Health.

The study examined information from more than 1 million adults with dementia discharged from French hospitals from 2008 to 2013.

Researchers said more than a third of the 57,000 cases of early onset dementia they documented were directly alcohol-related. Another 18 percent of those people had been diagnosed with an alcohol use disorder.

Researchers said the findings indicate that alcohol use disorders are associated with three times greater risk for all types of dementia.

Dr. Michaël Schwarzinger, a scientist at the French Translational Health Economics Network and lead study author, told Healthline, “We concluded that alcohol use disorders were the most significant modifiable risk factor for dementia onset and remained so after controlling for 30 possible or potential risk factors. In addition to their direct neurotoxic effect, alcohol use disorders were associated with all other modifiable risk factors like smoking, high blood pressure, diabetes, less education, and hearing loss. This suggests that the overall contribution of alcohol use disorders to dementia onset is even higher.”

The results came as a surprise to some researchers.

“We hypothesized that alcohol would play some role, but I don’t think anyone expected the size of the effect to be so large,” Dr. Jürgen Rehm, director of the University of Toronto’s Center for Addiction and Mental Health’s Institute for Mental Health Policy Research and a lead study author, told Time magazine.

Schwarzinger said there’s “conflicting evidence” on the benefits and harms of light to moderate alcohol use on dementia risk.

But, he said, “the strength of the association” uncovered in this study leads him to conclude the thresholds for “heavy drinking” should be lowered.

The Centers for Disease Control and Prevention defines heavy drinking as 15 or more drinks per week for men and 8 or more drinks per week for women.

Dr. Joseph Garbely, vice president of medical services and medical director at Caron Treatment Centers, is of the belief that alcohol affects the brain, especially in older adults.

“Alcohol consumption causes cognitive abnormalities because alcohol has amnesia-like effects,” Garbely told Healthline. “It impairs your ability to encode new memories, which is where the term ‘black out’ comes into play. Although the effects of alcohol use include reduced short-term memory, it can affect other areas of memory in the brain as well, mimicking the symptoms of dementia, and because it targets higher-executive functioning of the brain, the impairment to an older adult’s cognitive capability is much higher.”

Schwarzinger said that while “the neurotoxic effects of heavy drinking have been known for decades, this study confirms both the major neurotoxic effect of heavy drinking on the brain as well as the strong associations of heavy drinking with all other independent risk factors for dementia onset.”

“A growing body of neuroimaging studies support that alcohol use is directly correlated with brain damage,” added Schwarzinger.

Dr. Ming Wang, a staff physician at Caron Treatment Centers, notes that drinking can spiral out of control, making a bad situation even more serious.

“Alcohol’s effect on the prefrontal cortex leads to cravings and a preoccupation with drinking,” Wang told Healthline. “Alcohol-induced conditioning then causes increased alcohol use that further erodes a person’s decision-making abilities. Alcohol also reduces serotonin levels in the cerebral spinal fluid. This has been linked to a loss of behavioral control that can lead to uncontrolled drinking.”

Keith Fargo, PhD, director of scientific programs and outreach for the Alzheimer’s Association, said the latest research is another confirmation of what he considers to be a “known link” between heavy drinking and dementia risk.

“It’s a confirmation of what people have long suspected,” he told Healthline.

Fargo noted that drinking is linked to “all-cause dementia,” but so far there isn’t a proven connection between heavier drinking and Alzheimer’s, the most common form of dementia.

Fargo also said there’s conflicting research on whether light or moderate drinking increases the risk of dementia.

He said there are studies that show a drink or two a day can be good for cardiovascular health and that, in turn, can be good for the brain because of its need for blood flow and oxygen.

“Something that is good for your cardiovascular health is good for your brain as you age,” Fargo said.

Fargo added there’s also conflicting research on whether light or moderate drinking is harmful to someone who has developed dementia.

However, family members who are concerned about the drinking habits of someone with dementia may have a difficult time convincing that person to stop.

Dementia, Fargo noted, is more than just a loss of memory. It can also involve a loss of judgment and decision-making abilities.

He compared drinking issues with forcing a person with dementia to give up driving.

The Alzheimer’s Association does have a 24-hour hotline staffed with social workers that can help family members with these and other issues.

The toll-free hotline number is 800-272-3900.