Alcohol is a psychoactive substance that is socially accepted and widely consumed in many, but not all, parts of the world. It is estimated that in 2013, 22 million Canadians drank alcohol in the previous year – that is nearly 80% of the population. In 2015 in the U.S., 70.1% of individuals aged 18 years old and over indicated that they consumed alcohol in the past year.
A PSYCHOACTIVE SUBSTANCE changes brain function, resulting in temporary alterations to perception, mood, consciousness and/or behaviour.
Despite how commonplace alcohol consumption is, it is not a risk-free activity. Drinking is associated with many health problems including increased risk of certain cancers, high blood pressure, heart disease, and diabetes. According to the World Health Organization, approximately 3.3 million deaths (or 5.9% of all global deaths) were attributable to alcohol consumption in 2012.
CONSUMING ALCOHOL ALSO IMPACTS BRAIN HEALTH SINCE THE BRAIN IS ESPECIALLY VULNERABLE TO ITS TOXIC EFFECTS.
However, the exact relationship between alcohol and brain health is complex – affected by the total quantity of alcohol consumed, consumption patterns, the age and sex of the drinker, and even possibly genetics – and the relationship is not yet fully understood.
THE EFFECTS OF LIGHT-TO-MODERATE ALCOHOL CONSUMPTION
There is almost universal agreement that heavy drinking is associated with cognitive impairment, but some studies have suggested that light-to-moderate alcohol consumption may protect against cognitive decline and help lower the risk of dementia. A recent study conducted by Dr. Iben Lundgaard and her colleagues found that low doses of alcohol have a positive effect on brain health.
As part of this study, the researchers gave mice low doses of alcohol – 0.5g/kg, the equivalent of 2.6 drinks for a 70kg person – and then observed the impact on their glymphatic pathway func- tion. The glymphatic pathway is a complex system in the brain (for humans, too) that clears wastes and other harmful substances, including amyloid beta and tau proteins, which are both hallmarks of Alzheimer’s disease.
The researchers discovered that the low dose of alcohol significantly improved the mice’s glymphatic activity, regardless of whether the mice received just one dose of alcohol or chronic expo- sure over 30 days. This boost in glymphatic function may explain the lowered risk of dementia that has been noted among light alcohol drinkers in other studies. These findings were shared in February 2018 in Scientific Reports.
IT IS IMPORTANT TO NOTE, THOUGH, THAT MANY STUDIES ABOUT THE BENEFITS OF LIGHT-TO-MODERATE DRINKING (LMD) HAD METHODOLOGICAL LIMITATIONS AND MANY OF THE RESEARCHERS WARNED THAT THEIR FINDINGS NEED TO BE INTERPRETED WITH CAUTION.
For example, Dr. Iben Lundgaard and her colleagues warn that their findings on mice “should not be viewed as a recommendation for alcohol consumption guidelines in humans.”
Moreover, research to date on the effects of light-to-moderate alcohol consumption is inconsistent. By way of contrast, a recent U.K. study conducted by Topiwala et al. – published in The BMJ in 2017 – casts doubt on any potential claims of a brain health boost from light-to- moderate drinking. The researchers found that moderate drinkers were three times more likely than those who do not drink at all to experience shrinking of the hippocampus, and very light drinking did not offer any protection compared to abstinence.
In an accompanying editorial, Dr. Killian A. Welch, a neuropsychiatrist from the U.K., discussed these findings in the context of the broader research base. In his view, as the intake of alcohol increases, so does the risk to one’s health.“ Heavy consumption is associated with potentially severe impairments in memory and executive function, but lower quantities in the range many people consider ‘normal’ can also have adverse consequences for brain health. Because of the uncertainty around any potential benefits, no one should ever start drinking alcohol, even in small amounts, in an attempt to improve brain health,” Dr. Welch emphasized.
One of the challenges with conducting research about alcohol consumption is the lack of universal definitions of a “standard” size for a single serving of alcohol and how many servings constitute “light,” “moderate” or “heavy” drinking. Consequently, it is difficult to compare results across studies. Yet, Jee Wook Kim and his colleagues attempted to do just that in their review article, published in Psychiatry Investigation in 2012. These researchers reviewed studies published between 1971 and 2011 related to alcohol and cognition, specifically in the elderly. They found that studies of the influence of LMD on cognition reported varying results and they referred to the outcomes of those studies as “controversial.”
It is possible that the reason why researchers are struggling to determine whether LMD has cognitive benefits or not is because the answer might differ based on certain characteristics or conditions. For example, one study found that alcohol improved cognitive function only in patients with cardiovascular disease or diabetes, while other studies have reported that elderly women experienced the benefits of alcohol, but not men.
THERE MAY EVEN BE A GENETIC EXPLANATION FOR WHY SOME INDIVIDUALS SEEM TO BE MORE SUSCEPTIBLE TO ALCOHOL-INDUCED NEUROTOXICITY.
It appears that people with the apolipoprotein E epsilon 4 allele (APOE e4) are more susceptible to the negative effects of alcohol. Dr. Brian Downer and his colleagues in the U.S. reported in Alcohol and Alcoholism, published online in September 2013, that “light and moderate alcohol consumption during late life was associated with greater decline in learning and memory among APOE e4 carriers, whereas light and moderate alcohol consumption was associated with an increase in learning and memory among non-APOE e4 carriers.”
- Apolipoprotein E (APOE) is the gene most commonly associated with late-onset Alzheimer’s disease (AD). It has three forms (called alleles):
- APOE e2 is the least common and appears to reduce the risk of AD;
- APOE e4 is slightly more common than e2 and appears to increase the risk of AD; and
- APOE e3 is the most common and does not appear to impact the risk of AD.
Age may also play a role in the impact of alcohol on the brain. Older individuals are less able to metabolize alcohol and their brains are more sensitive to it compared to younger individuals, possibly making the effect of alcohol more potent for seniors – especially with regard to cognition.
THE EFFECTS OF ALCOHOL MISUSE
Excessive drinking has an immediate neurotoxic effect that impairs cognitive performance and may lead to “blacking out” – a full or partial experience of memory impairment while intoxicated. The impact of high amounts of alcohol on cognitive performance extends well beyond the intoxication period, starting immediately after an episode of drinking during a hangover. Studies have found that people suffering from a hangover (but with alcohol levels at zero) experienced a decline in memory, attention, psychomotor performance and executive function when asked to complete complex tasks.
When a person consumes excessive amounts of alcohol – either through heavy drinking or binge drinking – particularly over a long period of time, the consequences to his or her brain health can be quite severe, affecting both the structure and function of the brain. The umbrella term widely used to describe the range of potential disorders caused by too much alcohol is “alcohol-related brain damage” or “ARBD.” It is estimated that ARBD may account for 10% of early-onset dementia and possibly 10%-24% of dementia cases in nursing homes.
Below is a summary of some of the ways excessive drinking has been found to affect brain health.
BINGE DRINKING BY ADULTS AGED 65 YEARS AND OLDER NEGATIVELY AFFECTS COGNITIVE FUNCTION AND MEMORY.
In a study that analyzed data from over 5,000 U.S. adults aged 65 years and older, researchers found that those who reported binge drinking at least twice each month were 2.5 times more likely to experience higher levels of decline in cognitive function and memory over the eight-year study period. Outcomes were similar in women and men. In this study, binge drinking was defined as consuming four or more drinks on one occasion. This research was led by Dr. Iain Lang from University of Exeter in the U.K., and the results were presented at the Alzheimer’s Association International Conference 2012 in Vancouver, Canada.
EXCESSIVE DRINKING IN MIDLIFE SUBSTANTIALLY INCREASES THE RISK OF DEMENTIA LATER IN LIFE.
Researchers in Finland – Tarja Jürvenpää and colleagues – examined data from 554 Finnish twins who provided information about their alcohol consumption at two different times (in 1975 and 1981) and were later assessed for dementia (once they were over the age of 65, between 1999 and 2001). The results indicated that those who reported binge drinking in 1975 (i.e. consumed more than five bottles of beer or a bottle of wine on one occasion at least monthly) were 3.2 times more likely to have dementia when they were over the age of 65. The researchers also found that participants who reported in 1981 that they had passed out at least twice from excessive alcohol in the previous year were 10.5 times more likely to develop dementia later in life. These results were reported in 2005 in Epidemiology.
EXCESSIVE DRINKING CAN LEAD TO A MEMORY DISORDER REFERRED TO AS “KORSAKOFF SYNDROME,” WHICH IS CAUSED BY A SEVERE DEFICIENCY OF THIAMINE (VITAMIN B-1).
Alcohol is known to contribute to thiamine deficiency and thiamine is an essential nutrient for brain function. Korsakoff Syndrome makes it difficult to learn new information and remember recent events, and can cause long-term memory gaps. Korsakoff Syndrome often, but not always, follows an episode of Wernicke Encephalopathy – a medical emergency involving a life-threatening brain reaction to severe thiamine deficiency. Sometimes the two conditions are referred to collectively as Wernicke-Korsakoff Syndrome. When Wernicke Encephalopathy goes untreated, it leads to death in as many as 20% of cases and progresses to Korsakoff Syndrome in 85% of survivors.
Thiamine deficiency is not the only mechanism through which excessive drinking can affect brain health. Alcohol misuse can also lead to brain damage through the direct neurotoxicity of alcohol, alcohol-related cerebrovascular disease, and head injuries that occur while drunk.
Sadly, alcohol misuse is quite common. Rates of alcohol use disorders vary significantly across the globe but are estimated to range up to a high of 16% of the population in some areas.
The good news is that people with alcohol-related disorders that affect the brain can sometimes partially recover if they stop drinking alcohol permanently. Older drinkers, however, are less likely to recover even when they stop drinking.
When someone consumes a high number of alcoholic beverages in a given week, it is considered HEAVY DRINKING. According to the Centers for Disease Control and Prevention (CDC) in the U.S., this is considered 8 or more drinks for women and 15 or more drinks for men. It is considered BINGE DRINKING when someone consumes a high number of alcoholic beverages on one occasion: 4 or more drinks for women, 5 or more drinks for men. **
“Standard” drink sizes vary from country to country. For instance, in the U.K. a “standard” drink contains 8 grams of alcohol, versus 10 grams in Australia, 13.6 grams in Canada, 14 grams in the U.S., and 19.75 grams in Japan. Additionally, definitions of “high” levels of alcohol consumption could range from 10 “standard” drinks a week to more than 9 “standard” drinks each day.
Click here to read original article in Mind Over Matter Volume 6, page 10.
** In January 2023, The Canadian Centre on Substance Use and Addiction issued Canada’s Guidance on Alcohol and Health, updating its 2011 Low Risk Drinking Guidelines. The new guidance states that no amount of alcohol is safe. It presents a continuum of risk and indicates that the risk of alcohol-related consequences begins to increase when consuming more than two standard drinks per week, which is considered low risk. Moderate risk is considered to be three to six standard drinks per week, where the risk of developing several cancers increases, while seven or more standard drinks — considered increasingly high risk — raises the risk of heart disease and stroke. – Dalhousie University
