Loss of consciousness due to alcohol consumption is strongly associated with an increased risk for dementia irrespective of overall alcohol consumption, according to results of a study published in JAMA Network.
Studies have suggested an association of alcohol use with an increased risk for dementia, but the role of drinking patterns in the development of dementia in the general population has not yet been determined.
To determine the association between dementia occurrence and average alcohol consumption and alcohol-induced loss of consciousness, questionnaire data from 131,415 (61.1% women) were analyzed. The mean age of participants was 43.0±10.4. Two definitions of heavy and moderate drinking were used in the analysis. UK Chief Medical offices define heavy drinking as the weekly consumption of >112g (>14 units [U]) of ethanol and moderate drinking as the weekly consumption of 1-14 U. The United States National Institute of Alcohol Abuse and Alcoholism defines heavy drinking as the weekly consumption of >21 U of alcohol and moderate drinking as the weekly consumption of 1-21 U of alcohol.
According to UK guidelines, 78.6% of participants were moderate drinkers and 21.4% were heavy drinkers at baseline. Of the heavy drinkers, 64.1% were men. A moderate association between heavy alcohol consumption and the development of dementia (hazard ratio [HR], 1.16; 95% CI, 0.98-1.37) compared with moderate drinking was observed. When using the US threshold for heavy drinking, a greater association was observed (HR, 1.22; 95% CI, 1.01-1.48). Of the 96,951 individuals who lost consciousness after drinking, 79.8% had moderate alcohol consumption and 20.2% had heavy alcohol consumption, according to UK guidelines. When controlling for overall alcohol consumption, an increase in incidence of dementia was associated with losing consciousness once (HR, 2.10; 95% CI, 1.42-3.11) and more than once (HR, 2.19; 95% CI, 1.40-3.42) compared with individuals who did not lose consciousness.
The results of this study indicated that loss of consciousness due to alcohol consumption is associated with a 2-fold increase in risk for dementia, irrespective of overall alcohol consumption. Ethanol is neurotoxic and may directly cause brain damage through its metabolite acetaldehyde.
Limitations to the study include the difficulty in delineating going to sleep after excessive alcohol intake and true alcohol-related loss of consciousness, resulting in a likely overestimation of alcohol-related loss of consciousness. Another limitation is the reliance on self-reported data, which is not always accurate. Further studies investigating the association of alcohol-related loss of consciousness and dementia in other cultures is warranted.
Kivimäki M, Sing-Manoux A, Batt GD, et al. Association of alcohol-induced loss of consciousness and overall alcohol consumption with risk for dementia [published online September 9, 2020]. JAMA Network. doi: 10.1001/jamanetworkopen.2020.16084