Probiotic Supplementation Improves the Clinical Measures of Cognition in Patients With Mild Cognitive Impairment

Mild cognitive impairment progresses slowly and may be reversible, providing a window of opportunity for intervention before it progresses to Alzheimer's disease, at which point treatments, at best, ameliorate symptoms with little efficacy towards delaying disease progression. The gut and brain communicate through the gut-brain axis, and derangement of the gut microbiome has been shown to promote neuroinflammation, a process intricately linked to pathological progression to mild cognitive impairment and subsequent neurocognitive diseases. In preclinical trials, probiotics modulated the gut microbiome in a way that was neuroprotective. We aim to test our hypothesis that probiotic supplementation can improve cognition in those with mild cognitive impairment. A literature search of electronic databases PubMed/MEDLINE using terms such as "Probiotics" and "Cognitive dysfunction" or "Alzheimer's disease" or "Mild Cognitive Impairment" was done to identify all randomized controlled trials that tested our hypothesis. The effects of daily doses of <i>Bifidobacterium</i>, <i>Lactobacillus</i>, or a mixture of both on clinical cognitive tests were assessed in five trials. All studies but one demonstrated a statistically significant improvement in total cognitive test scores, while all studies showed a significant improvement over the placebo in at least one cognitive subdomain. An overall trend suggested greater improvement in those more severely impaired at baseline. Thus, probiotics may be effective in improving cognition in those with mild cognitive impairment. However, larger-scale multicenter clinical trials should confirm the present findings using a standardized approach.