Association of Trimethylamine-N-Oxide Levels with Risk of Cardiovascular Disease and Mortality among Elderly Subjects: A Systematic Review and Meta-Analysis

Background: Trimethylamine-N-Oxide (TMAO) is a microbiome-related metabolite that has been linked to cardiovascular and renal function. This study has reviewed and analyzed the relationship between TMAO and all-cause mortality and adverse cardiovascular events in elderly subjects. Methods: We determined whether this association was modified in the presence of chronic kidney disease (CKD), heart failure (HF), and diabetes. Based on the criteria, systematic review and meta-analysis were conducted and performed. Results: A total of 27 prospective cohort studies were retrieved finally to examine the associations. The high TMAO was positively associated with all-cause mortality (hazard ratio (HR): 1.38 [95% confidence interval (CI): 1.306–1.460]) as well as adverse cardiovascular events (HR: 1.032 [95% CI: 1.014–1.051]). The association remained upon subgroup analysis for patients with CKD and HF but no association found for the patients with diabetes (HR: 1.15 [95% CI, 0.81–1.64]). Conclusions: The findings of this review revealed that the TMAO level is associated with all-cause mortality and adverse cardiovascular events.