A history of alcohol-induced loss of consciousness is associated with a significant increase in the risk for dementia, irrespective of the overall alcohol consumption, according to study results published in JAMA Network Open.

Previous studies have established that alcohol use disorder is associated with an increased risk for dementia. However, the role of overall alcohol consumption and alcohol-induced loss of consciousness is not clearly defined. The objective of this study was to determine the association of alcohol consumption and alcohol-induced loss of consciousness with the risk of future dementia.

Using data from the individual-participant data meta-analysis in working populations’ consortium, study researchers collected data on alcohol consumption of 131,415 (mean age, 43.0 years; 61.1% women) current drinkers from the UK, France, Sweden, and Finland. All participants were aged 18 to 77 years at baseline, did not have a baseline diagnosis of dementia, and were linked to electronic health records for incident dementia follow-up.


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During a mean follow-up of 14.4 years, 1081 (0.8%) of the current drinkers developed all-cause dementia. 

Across the 7 cohorts, the risk for dementia was increased by 16% among heavy drinkers (>14 Units/week), compared with moderate alcohol consumption (1-14 Units/week) (hazard ratio [HR], 1.16; 95% CI, 0.98-1.37). Among those who consumed more than 21 weekly units of alcohol, the risk was increased by 22% (HR, 1.22; 95% CI, 1.01-1.48), compared with consumption of 1-21 weekly units.

Additional data on loss of consciousness was available for 96,591 subjects from 2 studies. Of these, 10,004 participants (10.4%) reported a history of alcohol-induced loss of consciousness within the last 12 months. This group included 5223 moderate drinkers and 4781 heavy drinkers.

Statistical analyses indicated that alcohol-induced loss of consciousness was associated with an increased risk for dementia in both men (HR, 2.86; 95% CI, 1.77-4.63) and women (HR, 2.09; 95% CI, 1.34-3.25).

Alcohol-induced loss of consciousness was also associated with increased risk for early-onset (<65 years) and late-onset (≥65 years) all-cause dementia. While the risk for Alzheimer disease was 2-fold greater for patients with a history of alcohol-induced loss of consciousness (HR, 1.98; 95% CI, 1.28-3.07), the risk for dementia with features of atherosclerotic cardiovascular disease was 4-fold greater, compared to patients without a history of alcohol-induced loss of consciousness (HR, 4.18; 95% CI, 1.86-9.37).

The risk for dementia was increased in individuals with a history of alcohol-induced loss of consciousness, whether they reported moderate (HR, 2.19; 95% CI, 1.42-3.37) or heavy (HR, 2.36; 95% CI, 1.57-3.54) average alcohol consumption.

To minimize reverse causation, assessment of the risk for dementia was completed in the first 10 years of follow-up (HR, 2.72; 95% CI, 1.78-4.15) and after exclusion of the first 10 years of follow-up (HR, 1.86; 95% CI, 1.16-2.99).

The study had several limitations, including those related to obtaining data from electronic health records; potential unmeasured confounders such as falls and repeated head injury, which may contribute to increased risk for dementia; and data limited to high-income countries, limiting its generalizability to countries with different drinking habits.

“This increased risk suggests that the drinking pattern is important vs just the overall weekly quantity consumed. These findings add to the knowledge base about the implications of alcohol misuse on the brain,” concluded the study researchers.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Kivimäki M, Singh-Manoux A, Batty GD, et al. Association of alcohol-induced loss of consciousness and overall alcohol consumption with risk for dementia. JAMA Netw Open. 2020;3(9):e2016084. doi:10.1001/jamanetworkopen.2020.16084