What is the impact of thiamine deficiency on cognitive function in patients with alcohol use disorder? - A systematic review

Cognitive impairments are frequently observed in patients with Alcohol Use Disorder (AUD). Thiamine deficiency is often found in AUD patients and has been suggested as a possible cause of cognitive impairments. While thiamine deficiency is not consistently present in all AUD patients with cognitive deficits, thiamine is traditionally prescribed to patients with AUD to treat or prevent cognitive impairment. To better understand the relationship between thiamine levels and cognitive impairments in AUD patients, we conducted a systematic literature review following the Cochrane guidelines and adhering to the PRISMA-P framework. Additionally, this review is registered in PROSPERO under the reference CRD42024522058. Our research question was: "what is the impact of thiamine deficiency on cognitive function in patients with AUD?". The studies included in this review assessed thiamine levels in AUD patients and found values at or above the threshold for many measures of thiamine deficiency. Despite baseline thiamine levels being above the cutoff for deficiency in these studies, many still identified a correlation between thiamine levels and cognitive function with lower thiamine levels associated with cognitive impairments in AUD patients. This review indicates that there is a relationship between thiamine levels and cognitive function in AUD patients, even in the absence of thiamine deficit. The cognitive domains particularly affected are visuospatial/ executive ability, abstraction, attention, verbal fluency, and memory scores, notably delayed memory. Additionally, studies have demonstrated that thiamine supplementation in AUD patients, even in the absence of thiamine deficit, leads to improvements in cognitive function.