Serum branched amino acids and the risk of all-cause mortality: a meta-analysis and systematic review

Recently, the serum levels of branched-chain amino acids (BCAAs) have been considered as an indicator to evaluate health status and predict chronic diseases risk. This systematic review and meta-analysis aimed to assess the relationship between Serum BCAAs and the risk of all-cause mortality. We carried out a comprehensive and systematic search in various important databases, including PubMed, Scopus, and Web of Science databases to find the relevant studies published up to October 2022 with no language, design, or time limitation. We extracted the reported hazard ratio (HR) with 95% confidence interval (CI) and odds ratio (OR) with 95%CI in cohorts and case–control studies, respectively, and computed the log HR or OR and its standard error. Then, we used the random-effects model with inverse variance weighting method for the present meta-analysis, to calculate the pooled effect size. Ten observational studies, including nine cohort studies and one case–control study, were included in the present meta-analysis. The number of participants ranges from 53 to 26,711, with an age range of 18–99 years. During 6 months to 24 years of follow-up, 3599 deaths were ascertained. The pooled results indicated that there was no significant association between serum BCAAs (RR: 1.17; 95% CI 0.85–1.60), isoleucine (RR: 1.41; 95%CI 0.92–2.17), leucine (RR: 1.13; 95% CI 0.94–1.36), and valine (RR: 1.02; 95%CI 0.86–1.22) and all-cause mortality. Also, there was significant heterogeneity between studies for serum BCAAs (I² = 74.1% and P-heterogeneity = 0.021), isoleucine (I² = 89.4% and P-heterogeneity < 0.001), leucine (I² = 87.8% and P-heterogeneity < 0.001), and valine (I² = 86.6% and P-heterogeneity < 0.001). Our results suggested that the serum BCAAs and its components, including isoleucine, leucine, and valine, were not associated with the risk of all-cause mortality.