Alcohol Use, Thiamine Deficiency, and Cognitive Impairment

To the Editor: In his Clinical Crossroads article, Dr Brust¹ discussed the patient Mr E, an older, moderate to heavy alcohol drinker experiencing memory difficulty and an apparently unrelated polyneuropathy. Mild cognitive impairment (MCI), early Alzheimer disease (AD), Wernicke-Korsakoff syndrome, and “alcoholic dementia” were considered as possible diagnoses. Appropriate management of the suggested diagnosis of MCI or early AD for this patient included measures to reduce alcohol dependence and to delay progression of the cognitive impairment. However, many epidemiological studies have failed to identify a positive relationship between moderate alcohol intake (usually up to 1 or 2 drinks daily) and risk of dementia, and they have also found such amounts to be protective.^{2 - 3}

We evaluated the association of alcohol consumption and the incidence of MCI in 1445 non–cognitively impaired individuals and on its progression to dementia in 121 patients with MCI aged 65 to 84 years participating in the Italian Longitudinal Study on Aging, with a 3.5-year follow-up.³ Patients with MCI who consumed up to 1 drink per day had a lower rate of progression to dementia in comparison with patients with MCI who never consumed alcohol. Overall, compared with nondrinkers, patients with MCI who consumed 1.0 to 14.9 g of alcohol per day derived mostly from wine had an 85% lower rate of progression to dementia. No significant associations were found between any levels of drinking and the incidence of MCI in non–cognitively impaired individuals vs abstainers. To the best of our knowledge, only 2 other studies have examined the association of alcohol consumption and the risk of MCI.^{4 - 5}

It is possible that moderate lifestyles in general, which will vary according to different cultural environments, protect from cognitive impairment. Thus, it may not be the direct effect of alcohol or specific substances in alcoholic drinks that might provide protection, but moderate alcohol drinking may be an indicator of a complex set of favorable social and lifestyle factors. A protective effect of alcohol on cognitive function in moderate drinkers could be due to a relatively poor health status among abstainers or because cognitive status influences alcohol consumption and overall health status.

Among management options, Dr Brust included total abstinence from alcohol, but given the observational evidence that moderate alcohol intake may be linked to a protective effect against MCI and dementia,^{2 - 4} the uncertain role of alcohol in contributing to either polyneuropathy or cognitive impairment, and the challenge in achieving total abstinence, a viable alternative option for this patient could also be moderate drinking (1.0 to 14.9 g of alcohol per day).