Association between levels of trimethylamine N-oxide and cognitive dysfunction: a systematic review and meta-analysis

Previous studies have shown that the differential expression of trimethylamine N-oxide (TMAO) is closely related to the prognosis of cognitive dysfunction, but the conclusion is still controversial. Therefore, we conducted a meta-analysis to investigate the difference of TMAO levels between patients with and without cognitive dysfunction.

From the beginning to January 25, 2024, we search for correlational studies on PubMed, Embase, Scopus, the Cochrane Library, and Web of Science. We sought to evaluate the association between TMAO, a major gut microbial metabolite, and cognitive function.

To investigate the differences in TMAO values between patients with and without cognitive dysfunction. The database search identified 229 studies. After applying exclusion criteria, seven studies involving 1,675 people (352 patients with cognitive dysfunction and 1,323 controls) were finally included in the meta-analysis. Compared with the control group, patients with cognitive dysfunction had significantly higher TMAO (standard mean differences (SMD): 1.21, 95% confidence interval (CI) [0.53-1.89], p = 0.0005, I ²:96%).

Patients with cognitive dysfunction have elevated TMAO levels, and TMAO levels are correlated with cognitive dysfunction.