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A recent study published in the journal Alcohol provides evidence that even low-level drinking may have negative consequences for brain health over a person’s lifespan. The findings suggest that the total amount of alcohol consumed over a lifetime, especially as a person ages, tends to be linked to reduced blood flow and thinner tissue in certain areas of the brain. These structural and functional brain differences indicate that the concept of low-risk drinking guidelines might need to be reevaluated.
For many years, public health guidelines suggested that consuming small amounts of alcohol carried minimal health risks. Today, more recent large-scale research provides evidence that the risks for various diseases begin to rise with any level of alcohol intake.
“There is increasing evidence that any alcohol consumption, even for what is currently considered ‘light drinking’ elevates risk for at least six different types of cancer, according to the World Health Organization,” said study author Timothy C. Durazzo, a professor at the Stanford University School of Medicine and a clinical neuropsychologist at the VA Palo Alto Health Care System.
“However, there has been little research devoted to studying the effect of low-level alcohol consumption on the human brain,” Durazzo explained. “We believed it was important to investigate the potential associations of low-level drink and measures of regional brain structure and blood flow (perfusion) in human adults.”
To explore these relationships, the researchers recruited healthy adults between the ages of 22 and 70. “Study participants were healthy, non-smoking adults, with no history of major medical or psychological conditions, who consumed less than or equal to 60 standard drink equivalents per month over the 1 year preceding study,” Durazzo noted. In the United States, a standard drink is defined as containing 14 grams of pure alcohol, which is roughly equivalent to a typical beer or a single glass of wine.
The researchers analyzed a total of 45 participants for brain volume and thickness measurements. A smaller group of 27 participants from this same pool underwent specialized scans to measure brain perfusion, which is the active delivery of blood to the brain’s tissues.
The scientists used detailed questionnaires to calculate each person’s average drinks per month over the past year, the past three years, and their entire lifetime. The participants then underwent magnetic resonance imaging scans.
These brain scans allowed the scientists to measure the physical volume and thickness of the cerebral cortex, which is the outer layer of the brain involved in high-level thinking and processing. For the perfusion group, the scans also tracked how much blood was actively flowing through various brain regions.
“The main findings were that a greater number of drinks consumed over lifetime, in combination with a higher age, were associated with decreased blood flow across the cortex (the outermost, folded layer of gray matter) as well as decreased thickness across the cortex,” Durazzo explained. Greater lifetime average drinking was associated with lower blood flow in 68 percent of the brain regions measured. These regions were spread out across multiple lobes of the brain.
The scientists found that the mathematical combination of advancing age and the total number of lifetime drinks was strongly linked to lower blood flow. This interaction was seen in nearly half of the measured brain regions, particularly in the frontal, parietal, and occipital lobes. “We did not expect the strength of the associations between greater number of drinks consumed over lifetime and higher age with decreased cortical blood flow to be as high as we observed,” Durazzo said.
Similar patterns were observed in the physical structure of the brain. Higher numbers of lifetime drinks were linked to a thinner cerebral cortex in multiple brain regions. When looking at the combination of age and total lifetime drinks, the scientists observed a thinner cortex mostly in the frontal and parietal lobes.
The frontal and parietal lobes are responsible for executive functions and sensory processing. Executive functions include mental skills like planning, focusing attention, and regulating emotions. The researchers suggest that these specific brain regions might be particularly vulnerable to the cellular wear and tear caused by alcohol consumption over time.
Cortical thickness is thought to reflect the density of brain cells, meaning a thinner cortex could indicate subtle cellular changes. The researchers suggest that oxidative stress might play a role in these changes. Oxidative stress is an imbalance in the body where unstable molecules cause damage to cells and tissues.
Alcohol consumption increases oxidative stress, and aging also tends to increase this cellular burden. This combined increase in cellular stress might explain why the interaction of age and lifetime drinking is linked to reduced brain tissue and lower blood flow. While the study provides new insights into low-level drinking, it has some limitations.
“The number of participants, particularly for the blood flow measures, was very modest (number of participants = 27 for blood flow measures and 45 for brain structural measures),” Durazzo pointed out. Because there were few female participants, the researchers could not look for differences based on biological sex. In addition, the scientists did not measure the actual speed of the blood flowing through the arteries.
Unmeasured lifestyle factors, such as diet and exercise habits, might also influence brain health and could explain some of the differences seen among participants. “We need to emphasize that the results from our study must be considered preliminary until they are replicated in a study with a larger number of participants,” Durazzo said.
Future research will need to replicate these findings in larger, more diverse groups of people. The researchers also want to look at how this combination of age and lifetime drinking affects everyday functioning. “It is unclear how our findings for cortical blood flow and thickness relate to important functions like balance and coordination,” Durazzo noted.
“Next steps are to investigate the associations of low-level drinking with measures of balance, coordination and dexterity,” Durazzo said. Understanding these functional outcomes will help clarify the real-world consequences of low-risk drinking guidelines.
The study, “The interaction of age and total lifetime drinks is associated with regional cortical perfusion and thickness in healthy adults with low-level alcohol consumption,” was authored by Timothy C. Durazzo, Brian D.P. Joseff, M. Windy McNerney, Keith Humphreys, and Dieter J. Meyerhoff.
