A recent study led by Dr. Louise Mewton at UNSW's Centre for Healthy Brain Aging (CHeBA) has reignited the debate about whether low levels of drinking could be positive for health.

The review, published in Addiction, has shown that abstaining from alcohol completely can actually increase the risk of dementia.

In recent decades, the estimated global prevalence of dementia has nearly tripled, from 20.2 million in 1990 to 57.4 million in 2019. By 2050, the projection is that there will be 152 million people globally living with dementia.

According to researchers, risk factor reduction is a fundamental strategy for prevention of dementia—particularly in light of the absence of disease-modifying treatments for dementia. A 2020 report from The Lancet Commission for Dementia Prevention, Intervention and Care estimated that 40% of global dementia cases could be prevented or delayed if 12 key modifiable risk factors for dementia were eliminated—with excessive or harmful alcohol use in midlife newly listed as one of those factors.

Dr. Mewton, who is Leader of the Risk Factors Group at CHeBA, said the inclusion of alcohol as a key risk factor for dementia was based on consistent and robust evidence indicating that chronic heavy alcohol use is associated with dementia and cognitive decline.

"There is controversy over the impact of more moderate levels of alcohol use on the incidence of dementia. Even low levels of alcohol use have been associated with poorer health outcomes, including increased cancer risk."

"They have also been associated with atrophy in key regions of the brain linked to dementia, like the hippocampus."

However, in this international study of nearly 25,000 community dwelling adults over the age of 65 including the United States, Australia, Europe, Brazil and the Republic of the Congo, it was consistently shown that abstaining from alcohol was associated with a higher risk of dementia.

"Our data came from 15 studies of healthy aging across six continents, and robust assessment of alcohol use and dementia," said Dr. Mewton. "Over the duration of the study 2,124 of the adults developed dementia. What we can conclude from our study is that there doesn't appear to be a need to intervene in those older adults currently drinking in a light to moderate pattern if dementia prevention is the ultimate goal."

The researchers found that individuals drinking up to four Australian standard drinks per day had a lower risk of dementia when compared with individuals who did not drink at all. The lower dementia risk associated with drinking alcohol was evident over and above the effects of demographic characteristics (such as age, sex and education), as well as clinical characteristics (such as history of stroke, diabetes and hypertension).

"It has been suggested that the increased risk of dementia associated with abstinence may be the result of including former drinkers who have ceased drinking due to other health conditions or the onset of cognitive problems."

"However, our study found an increased risk of dementia even after excluding former drinkers from the analysis and after adjusting for relevant demographic and clinical characteristics," said Dr. Mewton.

Despite this, there may be other characteristics such as social activity that could drive the apparent protective effect of alcohol against dementia, rather than alcohol use per se.

Senior author and Co-Director of CHeBA Professor Perminder Sachdev said that while light to moderate alcohol use may be associated with reduced dementia risk, even low levels of alcohol use have been associated with reduced brain volume, gray matter atrophy and increased white matter hyperintensities, indicating that even low level alcohol use is harmful to the brain.

--Heidi Douglass, CHeBA