How alcohol increases Alzheimer's risk
A cell-culture study using rodent microglia found that some of the genes affected by alcohol and inflammation are also implicated in processes that clear amyloid beta, suggesting that alcohol may impede the clearance of amyloid beta in the brain.
In the study, rat microglial cells were exposed either to alcohol, pro-inflammatory chemicals called cytokines, or alcohol and cytokines, for 24 hours. Gene expression was altered for 312 genes under the alcohol condition; for 3,082 for the pro-inflammatory condition, and 3,552 for the alcohol and pro-inflammatory condition. Changes in gene expression ranged from a 50% decrease to a 72% increase. Many of the genes were involved in phagocytosis; just a handful of genes were involved in both phagocytosis and inflammation.
Chronic heavy drinking trebles dementia risk
Data from the French National Hospital Discharge database, involving over a million people diagnosed with dementia between 2008 and 2013, found that 38% of the 57,000 cases of early-onset dementia were directly alcohol-related and 18% had an additional diagnosis of alcohol use disorders.
Overall, alcohol use disorders were associated with a three times greater risk of all types of dementia.
The study only looked at people admitted to hospital due to chronic heavy drinking, so it will understate the link between alcohol use and dementia risk.
Moreover, heavy drinkers who had given up alcohol for a time did not reduce their dementia risk (although they were less likely to die early).
(2018). Transcriptome analysis of alcohol-treated microglia reveals downregulation of beta amyloid phagocytosis.
Journal of Neuroinflammation. 15(1), 141.
(2018). Contribution of alcohol use disorders to the burden of dementia in France 2008–13: a nationwide retrospective cohort study.
The Lancet Public Health. 3(3), e124 - e132.