• New research finds that even moderate drinkers can double their risk of dementia, if they drink themselves unconscious — even rarely.
• Experts say there are long-term, irreversible effects of long-term alcohol exposure.
• Heavy drinking is considered eight or more drinks per week for women or greater than 14 drinks per week for men.

No one believes getting so drunk you pass out doesn’t have serious health consequences. However, a new study finds the price you pay involves much more than waking up with a hangover.

Researchers analyzed dementia diagnosis of over 130,000 people in Europe who had reported their drinking habits 14 years earlier. They found that those who reported losing consciousness after drinking had double the risk of dementia.

The risk was the same even if they were otherwise moderate drinkers, which is about a pint of beer or glass of wine per day.

According to the Centers for Disease Control and Prevention (CDC), Alzheimer’s disease is one of the top 10 leading causes of death in the United States.

Majority reported passing out from drinking

Scientists examined seven European cohort studies from the U.K., France, Sweden, and Finland to include 131,415 people.

The participants, aged between 18 and 77 years, weren’t diagnosed with dementia during the years when they reported their alcohol consumption (1986 to 2012).

At follow-up, an average of 14 years later, they were examined for symptoms of dementia.

Over 96,000 people in this group reported passing out due to alcohol. Of these, over 10,000 reported having lost consciousness from drinking in the past year.

“Binge drinking tends to be most problematic among college aged youth and young adults,” Dr. Scott Krakower, unit chief of psychiatry at Zucker Hillside Hospital, Glen Oaks, New York, told Healthline.

The moderate drinkers who hadn’t passed out while drinking were used as the reference group. Compared with other participants, those who reported alcohol-induced loss of consciousness were more likely to drink hard liquor and beer, rather than wine.

After excluding participants with early or late onset Alzheimer’s, and cardiovascular conditions to find risk of cognitive impairment, the study authors concluded, “The findings of this study suggest that alcohol-induced loss of consciousness, irrespective of overall alcohol consumption, is associated with a subsequent increase in the risk of dementia.”

How does drinking yourself unconscious affect the brain?

“It is felt that alcohol-induced blackouts are related to the effects of alcohol on the hippocampus,” said Dr. Kevin Conner, neurologist at Texas Health Arlington Memorial Hospital and Texas Health Physicians Group. “The hippocampus is the primary area of the brain that affects memory formation, storage, and retrieval.”

Conner explained that alcohol impairs an important part of the brain called glutamate receptors, which are necessary for brain cells to strengthen the transfer of information between neurons.

“This ultimately affects the retrieval of memory,” he said, adding that, “Additional brain injury can occur secondary to brain injuries related to falls, seizures, or asphyxiation from vomit, which may cause oxygen deprivation.”

Alcohol can cause irreversible damage

According to Conner, the brain may heal from alcohol-induced damage, “depending on the extent and duration of alcohol exposure.”

He explained that some memories may be recalled from a blackout if they’re “stimulated by outside influences, such as a smell, video, or auditory events that may trigger other pathways of memory.”

But he warned that there are long-term, irreversible effects of long-term alcohol exposure.

These include Wernicke-Korsakoff syndrome, “where there can be eye movement changes, balance difficulties, and confusion that may progress to full psychosis and dementia.”

Conner emphasized that irreversible brain shrinkage (atrophy) as well as nerve damage (peripheral neuropathy), are also related to long-term alcohol exposure. Also, “Liver failure can affect the brain, leading to somnolence, confusion, liver flap [tremors], coma, and death.”

What is excessive drinking?

According to the CDC, excessive drinking includes:

• Binge drinking, which is four or more drinks for women and five or more drinks for men during a single occasion.

• Heavy drinking, which is eight or more drinks per week for women or greater than 14 drinks per week for men.

Moderate drinking is defined as only one drink per day for women and two per day for men.

Alcohol and brain health, a complicated relationship

A 2018 study published in the British Medical Journal (BMJ) looked at over 9,000 people, aged 35 to 55 years when the study began, to find that both not drinking and excessive alcohol use in mid-life was associated with increased risk of dementia.

Researchers theorize that, since abstaining from alcohol increases the risk of diabetes and heart disease — two risk factors for cognitive decline — this may partly explain their findings.

“The long-term effects of moderate alcohol consumption defined as 14 drinks per week maximum, or two drinks max per day, have been shown to perhaps reduce the risk of dementia,” agreed Conner.

He pointed out that other studies have shown abstaining to have little to no effect, however: “Across almost all studies, though, higher levels of consumption have been shown to be detrimental to brain and cardiovascular health.”

The bottom line

New research finds that even moderate drinkers can double their risk of dementia, if they drink themselves unconscious — even rarely.

Experts say that alcohol impairs important parts of brain function, and while some alcohol-induced damage can heal, there is a significant risk of permanent injury.

The relationship between alcohol and health is complicated, with research also showing both abstaining from alcohol and excessive drinking in middle age may increase dementia risk.

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