92 year old Ali Haydar Cilasun (R) holds the hand of carer Guven Asmacik (L) in his room at an Aliacare home for the elderly in Berlin on October 8, 2013. The Aliacare home offers bilingual services for German and Turkish elderly people. AFP PHOTO / ODD ANDERSEN        (Photo credit should read ODD ANDERSEN/AFP/Getty Images)
92 year old Ali Haydar Cilasun (R) holds the hand of carer Guven Asmacik (L) in his room at an Aliacare home for the elderly in Berlin on October 8, 2013. The Aliacare home offers bilingual services for German and Turkish elderly people. AFP PHOTO / ODD ANDERSEN (Photo credit should read ODD ANDERSEN/AFP/Getty Images)
PHOTO: ODD ANDERSEN/AFP/AFP/Getty Images
Now playing
01:16
What is dementia?
PHOTO: CNN
Now playing
02:13
Why losing weight might protect you from Covid-19
A selection of fruit ready to eat are displayed at a fruit and vegetable shop on April 12, 2016 in Lille, northern France. / AFP / DENIS CHARLET        (Photo credit should read DENIS CHARLET/AFP/Getty Images)
A selection of fruit ready to eat are displayed at a fruit and vegetable shop on April 12, 2016 in Lille, northern France. / AFP / DENIS CHARLET (Photo credit should read DENIS CHARLET/AFP/Getty Images)
PHOTO: DENIS CHARLET/AFP/AFP/Getty Images
Now playing
01:27
New diet can save lives and the planet, study says
this is your brain on pain health orig_00001025.jpg
this is your brain on pain health orig_00001025.jpg
PHOTO: CNN
Now playing
01:39
This is your brain on pain
Now playing
01:42
Here's why you can't stop eating pizza, ice cream and chocolate chip cookies
Now playing
01:10
Trouble sleeping? This may be why
PHOTO: CNN
Now playing
02:40
The reality of wine's health benefits
PHOTO: shutterstock
Now playing
01:49
These foods aren't as healthy as you think
Americans are still too fat according to a new study from JAMA. Two in three of Americans are registering as overweight or obese.
Americans are still too fat according to a new study from JAMA. Two in three of Americans are registering as overweight or obese.
PHOTO: Shutterstock
Now playing
01:15
What is obesity?
PHOTO: CNN
Now playing
01:17
Why your BMI matters
LONDON - MAY 16:  In this photo illustration a cigarette is seen burning on May 16, 2007 in London. Businesses and shops are gearing up for the introduction of the smoking ban on July 1 in England after similar bans have been introduced in Ireland, Scotland and Wales.  (Photo Illustration by Bruno Vincent/Getty Images)
LONDON - MAY 16: In this photo illustration a cigarette is seen burning on May 16, 2007 in London. Businesses and shops are gearing up for the introduction of the smoking ban on July 1 in England after similar bans have been introduced in Ireland, Scotland and Wales. (Photo Illustration by Bruno Vincent/Getty Images)
PHOTO: Bruno Vincent/Getty Images Europe/Getty Images
Now playing
01:07
What tobacco does to your health (2017)
PHOTO: Photo Illustration/Thinkstock
Now playing
01:12
World blood pressure rises (2016)
Woman pointing to area on mammogram x-ray, close-up
Woman pointing to area on mammogram x-ray, close-up
PHOTO: Getty Images/File
Now playing
01:19
Breast cancer: Know the facts
A surgeon sitting in front of screens of a Focal One device performs a robot-assisted prostate tumorectomy using ultrasound imaging on April 10, 2014 at the Edouard Herriot hospital in Lyon, center France. Focal One is the first robotic HIFU (high intensity focused ultrasound) device dedicated to the focal approach for prostate cancer therapy. According to EDAP TMS SA, a leader in therapeutic ultrasound, it combines the three essential components to efficiently perform a focal treatment: state-of-the-art imaging to localized tumors with the use of magnetic resonance imaging (MRI) combined with real-time ultrasound, utmost precision of robotic HIFU treatment focused only on identified targeted cancer areas, and immediate feedback on treatment efficacy utilizing Contrast-Enhanced Ultrasound Imaging. AFP PHOTO / JEFF PACHOUD        (Photo credit should read JEFF PACHOUD/AFP/Getty Images)
A surgeon sitting in front of screens of a Focal One device performs a robot-assisted prostate tumorectomy using ultrasound imaging on April 10, 2014 at the Edouard Herriot hospital in Lyon, center France. Focal One is the first robotic HIFU (high intensity focused ultrasound) device dedicated to the focal approach for prostate cancer therapy. According to EDAP TMS SA, a leader in therapeutic ultrasound, it combines the three essential components to efficiently perform a focal treatment: state-of-the-art imaging to localized tumors with the use of magnetic resonance imaging (MRI) combined with real-time ultrasound, utmost precision of robotic HIFU treatment focused only on identified targeted cancer areas, and immediate feedback on treatment efficacy utilizing Contrast-Enhanced Ultrasound Imaging. AFP PHOTO / JEFF PACHOUD (Photo credit should read JEFF PACHOUD/AFP/Getty Images)
PHOTO: JEFF PACHOUD/AFP/AFP/Getty Images
Now playing
01:21
What is prostate cancer?
PHOTO: Argosy
Now playing
00:53
What is Parkinson's disease?
Now playing
01:38
How Alzheimer's destroys the brain

Story highlights

Research involved more than 1 million adult patients released from hospitals in France

Alcohol abuse was also associated with vascular risk factors, including high blood pressure

(CNN) —  

Excessive alcohol use could increase your risk for all types of dementia, particularly early-onset dementia, according to a new study.

The study, published Tuesday in the journal Lancet Public Health, looked at over 1 million adults released from French hospitals between 2008 and 2013 who were diagnosed with dementia, a clinical syndrome characterized by a progressive deterioration in cognitive ability.

Using data from the French National Hospital Discharge database, the researchers found that alcohol-use disorders were diagnosed in 16.5% of the men with dementia and 4% of the women with dementia – over twice as much as in those without dementia for both sexes.

Alcohol-use disorders refer to “the chronic harmful use of alcohol or alcohol dependence,” the researchers wrote.

In order to isolate the role of alcohol use, patients with neurological disorders such as Parkinson’s and Huntington’s, which can also lead to dementia, were excluded from the study.

“The most novel result is the large contribution of alcohol-use disorders to the burden of dementia over the lifespan,” said Dr. Michael Schwarzinger, a researcher at the Transitional Health Economics Network in Paris and a leading author of the study.

The association was particularly strong for those with early-onset dementia, diagnosed when the patient is younger than 65. Over half of the individuals in the early-onset group had alcohol-related dementia or an additional diagnosis of alcohol-use disorder.

“Given the strength of the association, what is the most surprising to me is that alcohol-use disorders had received so little interest in dementia research and public health policies,” Schwarzinger said.

How alcohol might damage the brain

Although many studies have shown a strong association between excessive alcohol use and dementia, this study is unique in its findings about early-onset dementia, according to Dr. Kostas Lyketsos, a neuropsychiatry professor and director of the Johns Hopkins Memory and Alzheimer’s Treatment Center who was not involved in the study.

“That is rather unique,” Lyketsos said. “It does remind us that alcoholics have shorter life expectancies.”

The study was also among the largest of its kind. But, according to Lyketsos, the large size could leave the study open to selection bias.

“There’s a tradeoff between size and precision of the variables,” he said. “The more people you have, the less confidence you have in the elements that go into the diagnosis of dementia.

“I also want to point out that this was really a sample of hospitalized individuals. It’s very unusual for people with dementia, at least in the milder stages, to be hospitalized,” he added.

Research suggests multiple ways heavy alcohol use can lead to dementia. First, ethanol and its byproduct acetaldehyde are known to have a toxic effect on the brain that can lead to long-term structural and functional brain damage, Schwarzinger says.

Heavy alcohol use can also lead to a condition called hepatic encephalopathy, characterized by a loss in brain function due to increases of ammonia in the blood caused by liver damage.

“Heavy drinking is also strongly associated with vascular risk factors such as high blood pressure or diabetes mellitus as well as cardiovascular diseases,” Schwarzinger added.

“Lastly, heavy drinking clusters (in) people with less education, smoking habits, and/or depression. All of these factors were found to be independent risk factors for dementia onset.”

Though heavy alcohol use increased the risk of dementia in general, the association was shown to be stronger in men.

When other factors were not controlled for, heavy drinking was associated with a higher risk of dementia among both men and women. In men, the risk was increased by a factor of 4.7, while in women, it increased by a factor of 4.3.

But even when the researchers controlled for factors like high blood pressure, obesity and tobacco smoking, heavy alcohol use was still associated with a more than threefold increase in dementia among both sexes.

Results differed by sex

The study also showed that the average age of dementia onset differed between men and women. Men were more likely to develop it a younger age and women at an older age.

“Gender differences on dementia onset have been puzzling for decades,” Schwarzinger said. “Men have a poorer lifestyle than women on average, in particular heavier alcohol consumption. Therefore, it is somewhat unsurprising that early-onset dementia identifies a cluster of men with alcohol use disorders.”

The gender difference could also result from the study’s methodology, according to Lyketsos.

“That was one of the reasons I’m a little concerned about selection bias,” he said. “There could be a gender effect on who goes to the hospital with dementia.”

Alcohol use was also not objectively measured in the participants, one of the study’s main limitations.

“We have no idea what is the level of drinks they were actually drinking,” Schwarzinger added. “That kind of information you can only get in a cohort study with a questionnaire.”

Follow CNN Health on Facebook and Twitter

  • See the latest news and share your comments with CNN Health on Facebook and Twitter.

Though the study had a very large sample size, it looked at individuals in only one country, making it difficult to generalize across cultures. According to a 2014 report from the World Health Organization, each person consumes an average of 12.2 liters of pure alcohol in France versus 9.2 liters in the United States.

But Schwarzinger cautioned that people outside France should still take the findings seriously: “While the rate of alcohol use disorders is lower in the USA, it remains substantial enough to be considered major risk factor for dementia onset.”

Correction: A previous version of this story misstated the title of Dr. Kostas Lyketsos. He is a professor of neuropsychiatry.