Association of beta-2-microglobulin with cardiovascular and all-cause mortality in the general and non-CKD population

β-2 microglobulin, a light chain in the major histocompatibility complex Class 1 molecule, is associated with mortality in dialysis or uremic patients. Current evidence on the relationship between beta-2-microglobulin (B2M) and mortality in the general and non-chronic kidney disease (CKD) population are limited and controversial. Data from the nutrition and health examination survey database and the nutrition and health examination survey linked mortality file were used. In total, 10,388 adults who had complete data for B2M were included. Weighted multivariable Cox proportional hazards regression models and regression splines were employed to evaluate the relationship between B2M with mortality. Moreover, subgroup and sensitivity analyses were performed. During a median follow up of 17.9 years (interquartile range 15.2–18.7), 2780 people died, 902 (32%) from cardiovascular disease. Restricted cubic splines showed that B2M is J-shaped nonlinear positively associated with all-cause mortality and cardiovascular disease mortality in the non-CKD and general population. Based on the multivariable adjustment model, the adjusted hazard ratios comparing the highest versus lowest quartile of the distribution of B2M were 2.50 (95% confidence interval: 1.90, 3.28) for all-cause mortality in the general population, 2.58 (95% confidence interval: 1.52, 4.37) for cardiovascular disease mortality in the general population, 2.58 (1.91, 3.49) for all-cause mortality in the non-CKD population and 2.62 (1.52, 4.53) for cardiovascular disease mortality in the non-CKD population. The positive associations between B2M and outcomes remained broadly significant across subgroups and sensitivity analyses. Higher B2M levels were associated with cardiovascular and all-cause mortality in the general and non-CKD population.