Alzheimer's disease (AD) is a common cause of dementia, with about half of all patients with dementia suffering from AD. The disease is incurable and irreversible and takes around 10 years to develop. Early symptoms are forgetfulness, difficulty in processing new information and minor deficits in physical coordination. At a later stage, speech, orientation and the power of abstract thought are disturbed, followed by behavioural disturbances and changes in personality. The final state is one of complete physical and mental deterioration.

Results of case-control studies give little reason to believe that alcohol use reduces the risk of any type of dementia, but prospective studies suggest that moderate drinking may protect against dementia in general and AD in particular.

However, it is premature to suggest that moderate drinking can protect against dementia and AD, and the results of studies may be confusing. Individuals presenting with clinical symptoms of dementia may already have reduced their alcohol consumption before being included in studies in which alcohol was found to have a protective effect. In contrast, individuals who noticed the first signs of forgetfulness could have changed their drinking habits. The other problem is that factors associated with dementia or AD may be mixed up. In some groups of individuals, smoking and drinking are often associated; it is not yet clear to what extent these factors counteract each other or whether their effects add to pre-existing risks of various forms of dementia. In summary, moderate alcohol consumption may have a beneficial effect on cognitive functioning and/or the risk of AD and dementia, but further prospective studies are required to confirm this hypothesis.