There is no safe amount of alcohol when it comes to dementia, study finds

When you drink may impact how alcohol affects your body, according to neurologist Dr. Richard Isaacson. (skynesher/E+/Getty Images via CNN Newsource)

Drinking any amount of alcohol increases your risk of dementia later in life, according to a new study that challenges prior research findings.

Some research has suggested light drinking — such as fewer than seven drinks a week — may be more neuroprotective than no alcohol at all. Those studies, however, focused on older people and didn’t differentiate between former drinkers and lifelong nondrinkers, thus potentially skewing the results, study authors said.

In the new study, published Tuesday in the journal BMJ Evidence-Based Medicine, researchers analyzed how certain genes linked to alcohol might impact how liquor consumption affects the brain.

“The genetic analyses results (showed) that even small amounts of alcohol could increase dementia risk,” said lead study author Anya Topiwala, a senior clinical researcher in the department of psychiatry at the University of Oxford in the United Kingdom.

“This is the largest study on the topic, and the combination of observational and genetic analyses was key,” Topiwala said via email.

The genetic analysis, called Mendelian randomization, has less risk of introducing a confounding or “spurious” variable to explain the alcohol-dementia relationship, Topiwala said.

Mendelian randomization also reduces the chance of reverse causation, such as dementia processes influencing drinking rather than the reverse, and it can also estimate the cumulative impact of alcohol consumption over a person’s entire life, Topiwala said. Observational studies, however, tend to capture a snapshot of mid- to late-life drinking habits, and depend on subject recall, which may not be accurate.

“This is a fairly complicated study that provides some, but not definitive evidence, that alcohol can harm the brain regardless of how much is consumed,” said neurologist Dr. Richard Isaacson, director of research at the Institute for Neurodegenerative Diseases in Florida. Isaacson, who conducts studies on cognitive improvement in people who are genetically at risk for Alzheimer’s disease, was not involved in the new study.

“In my clinic, we tell people with the APOE4 genetic variant, which is the most common genetic risk factor for Alzheimer’s, that drinking zero alcohol is best based on the available evidence,” he said in an email.

However, for people with less genetic risk for Alzheimer’s it often depends on “when” and “how” people drink, Isaacson added. For example, he said, two drinks before bed on an empty stomach several nights will have a more harmful effect on brain health compared with one drink a few times a week with an early dinner.

An emerging link between alcohol and dementia

The new study looked at data from nearly 560,000 people who participated in the U.K. Biobank, a longitudinal study that included participants from England, Scotland and Wales, and the US Million Veteran Program, or MVP, which includes people of European, African and Latin American ancestry.

In that observational part of the study, people provided self-reports of how much they drank, and researchers compared alcohol consumption with their risk of developing dementia over time.

“In the self-reporting study, people who reported consuming small amounts of alcohol (less than 7 drinks per week) had lower risk than heavy drinkers (more than 40 drinks per week),” said Tara Spires-Jones, professor of neurodegeneration and director of the Centre for Discovery Brain Sciences at the University of Edinburgh in Scotland, in a statement.

“Interestingly, in this part of the study, non-drinkers and people who reported never drinking actually had similar risk of dementia to people who drank heavily,” said Spires-Jones, who is also a group leader in the UK Dementia Research Institute in London. She was not involved in the study.

The study then examined genetics from 45 studies of dementia in 2.4 million people and compared genetic markers associated with alcohol use over a lifetime.

Higher genetic risk was associated with an increased risk of dementia, with a linear increase in dementia risk the higher the alcohol consumption, according to the study.

“There is a 15% higher dementia risk for 3 drinks per week compared to 1 drink per week across life,” Topiwala said.

In addition, a doubling in the genetic risk of alcohol dependency was associated with a 16% increase in dementia risk, according to the study.

“Neither part of the study can conclusively prove that alcohol use directly causes dementia,” Spires-Jones said. “But this adds to a large amount of similar data showing associations between alcohol intake and increased dementia risk, and fundamental neuroscience work has shown that alcohol is directly toxic to neurons in the brain.”