Dose-Response Association Between Bilirubin and Cardiovascular Disease: A Systematic Review and Meta-analysis

The association between bilirubin (BIL) and cardiovascular disease (CVD) remains controversial. We performed a meta-analysis of prospective studies to evaluate this association in the general population. We searched PubMed, EMBASE, Web of Science, Cochrane, and Scopus databases through to September 2021. The Newcastle-Ottawa Quality Assessment Scale was used to assess study quality. The pooled effect estimate was calculated by the fixed-effect model or random-effect model. We included 12 prospective studies (368 567 participants). The pooled risk ratio of CVD for the lowest vs highest groups of BIL levels was .75 (95% CI: .58-.97) with high heterogeneity (I2 = 87.5%, P < .001). Similar associations were observed for coronary heart disease and stroke. We further performed a "dose-response" meta-analysis, and a significant U-shaped relationship between circulating (most values were serum bilirubin, but a few were plasma bilirubin) BIL and CVD (P < .01) was observed. The lowest risk of CVD events was observed in participants with a BIL of 17-20 µmol/L in serum and/or plasma. In conclusion, there was a U-shaped dose-response relationship between BIL and CVD, especially for men. Further studies are needed to confirm our findings and identify the mechanisms involved as well as any prognostic or therapeutic potential.