Large study is “robust” evidence of link between chronic heavy drinking and dementiaBMJ 2018; 360 doi: https://doi.org/10.1136/bmj.k814 (Published 21 February 2018) Cite this as: BMJ 2018;360:k814
Chronic heavy drinking should be recognised as a major risk factor for dementia, especially early onset dementia, say researchers. Doctors should screen patients for heaving drinking and offer brief interventions to help reduce alcohol consumption if necessary, they wrote in Lancet Public Health.1
The French retrospective cohort study, which included data from over 31 million people, found a strong association between alcohol use disorders and all types of dementia, even after they controlled for potential confounding risk factors.
The relation between alcohol and dementia has been widely studied, with some studies showing a possible benefit of light to moderate drinking, while others have found a detrimental effect of heavy drinking on dementia risk. The World Health Organization defines chronic heavy drinking as consuming more than 60 g of pure alcohol a day for men (six small glasses of wine) and more than 40 g a day for women (four small glasses of wine).
The study, which had no funding, used data from the French national hospital discharge database, which holds details on all hospital admissions. Between 2008 and 2013 a total of 31.6 million people aged 20 or over were discharged from hospital, of whom more than 1.1 million had a diagnosis of some form of dementia. One in 20 of these cases (57 353) were early onset dementia (before the age of 65).
Over the same time period 945 512 cases of alcohol use disorder were diagnosed, with alcohol dependency diagnosed in 86% of the cases, according to ICD-10 codes. The study found that around 3% of cases of dementia were attributable to alcohol related brain damage, and other alcohol use disorders were recorded in almost 5% of dementia cases. The association was even stronger in early onset dementia: 57% of people with this diagnosis also had an alcohol use disorder.
Overall, alcohol use disorders were the strongest modifiable risk factor for dementia, with an adjusted hazard ratio of 3.34 (95% confidence interval 3.28 to 3.41) for women and 3.36 (3.31 to 3.41) for men.
Once alcohol related brain damage had been excluded, alcohol use disorders were still associated with a twofold increased risk of vascular and other dementias. Alcohol use disorders were also associated with other independent risk factors for dementia, such as smoking, hypertension, diabetes, lower education, depression, and hearing loss.
The researchers said that their findings indicated that the burden of dementia attributable to alcohol was much larger than previously thought and greater than that of recognised risk factors such as smoking, depression, and hypertension.
One limitation of the study was that stigma associated with alcohol use disorders meant that they were likely to be underreported. Only the most serious cases resulting in admission to hospital would be included in the study. However, the authors said that this bias meant that the effect of alcohol use disorders on onset of dementia was likely to be underestimated.
The study’s lead author, Michaël Schwarzinger, from the Translational Health Economics Network, said, “The link between dementia and alcohol use disorders needs further research but is likely a result of alcohol leading to permanent structural and functional brain damage. Alcohol use disorders also increase the risk of high blood pressure, diabetes, stroke, atrial fibrillation, and heart failure, which may in turn increase the risk of vascular dementia. Lastly, heavy drinking is associated with tobacco smoking, depression, and low educational attainment, which are also risk factors for dementia.”
Writing in a linked commentary, Clive Ballard, from the University of Exeter Medical School, said that the study was “immensely important and highlights the potential of alcohol use disorders, and possibly alcohol consumption, as modifiable risk factors for dementia prevention . . . In our view, this evidence is robust and we should move forward with clear public health messages about the relationship between both alcohol use disorders and alcohol consumption, respectively, and dementia.”2