MedicalResearch.com: What is the background for this study? What are the main findings?
Response: The association of heavy drinking with dementia has been known for decades. For instance, there is about no Wernicke–Korsakoff syndrome without heavy drinking and the syndrome was described in 1890. But this type of dementia is very rare. Also, heavy drinking is knowingly associated with multiple risk factors for dementia onset such as hypertension or diabetes. But heavy drinkers generally refuse to participate to cohort studies and declaration of alcohol use among participants is generally biased downward… So the study rationale is very strong, but supporting empirical evidence is quite scarce.
This nationwide study included all 31+ million adults discharged from hospitals over 6 years, i.e., 50% of the French population before 65 years old and 80% above that age. Of 1.1+ million adults diagnosed with dementia, one in twenty had an early-onset (before 65 years old). Heavy drinking was recorded in most (56%) early-onset dementia cases: two-third in men; one-third in women. In addition, the association of heavy drinking with dementia goes far beyond 65 years old, both directly (>3 times higher risk for dementia onset after controlling for more than 30 known risk factors for dementia) and indirectly as heavy drinking was associated with all other independent risk factors for dementia onset. Accordingly, heavy drinking had the largest effect on dementia risk of all independent modifiable risk factors such as hypertension or diabetes.
The effects were found whatever dementia case definition or population studies.
MedicalResearch.com: What should readers take away from your report?
Response: Healthcare providers should be aware that heavy drinking is not only associated with multiple life-threatening conditions but also dementia. Screening and treatment of alcohol problems are effective and cost-effective.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: Future studies are clearly needed to clarify the alcohol threshold where people significantly become at higher risk for dementia. Given the strength of the association found in our study, this threshold is certainly below 60g/day for men and 40g/day for women that defines heavy drinking and most likely below 30g/day for men and 20g/day for women that defines at risk consumption.
There is conflicting evidence out there on the benefits/harms of light/moderate alcohol use on dementia risk. Several cohort studies reported that the association follows a J-shape curve, with light/moderate consumption associated with benefits. Though, a growing body of neuroimaging studies support that alcohol use is directly correlated with brain damage which does not fit with a J-shape curve.
MedicalResearch.com: Is there anything else you would like to add?
Response: This study received no funding. It was conducted by researchers from Translational Health Economics Network (THEN); UMR 1137 INSERM–Université Paris Diderot, Sorbonne Paris Cité; INSERM U1219-Bordeaux Population Health, ISPED-Bordeaux School of Public Health; and Centre for Addiction and Mental Health, University of Toronto.
Michaël Schwarzinger, Bruce G Pollock, Omer S M Hasan, Carole Dufouil, Prof Jürgen Rehm, QalyDays Study Group. Contribution of alcohol use disorders to the burden of dementia in France 2008–13: a nationwide retrospective cohort study. The Lancet Public Health, 2018 DOI: 10.1016/S2468-2667(18)30022-7
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