Largest study of its kind finds alcohol use biggest risk factor for dementia. Alcohol use disorders are the most important preventable risk factors for the onset of all types of dementia, especially early-onset dementia. This according to a nationwide observational study of over one million adults diagnosed with dementia in France. Source 3n.
Maybe when people drink and usually forget what happen the next day is a sign that their is some truth to this. It makes sense to me.
Alcohol, due to its neurotoxic effect, produces brain and neuronal damage that is internal at the level of the Hippocampus, Hypothalamus and Cerebellum. This has a direct impact on memory and learning ability. Another affected area would be the Prefrontal Cortex, which is directly related to executive dysfunction.