LAUSR

OBJECTIVE We aimed to examine the relationship between serum 25-hydroxyvitamin D (25(OH)D) and all-cause, cause-specific mortality of patients with rheumatoid arthritis (RA). METHODS This cohort study included 1466 patients with RA from The National Health and Nutrition Examination Survey (NHANES) 2001-2014. Mortality status were obtained according to death certificate records from the National Death Index (NDI). Cox proportional risk models were used to estimate hazard ratios (HR) and 95% confidence interval (CI) for mortality. A generalized additive model, smooth curve fitting and 2-piecewise Cox proportional hazards models were established to address the nonlinearity between serum 25(OH)D and mortality. RESULTS A total of 1466 patients (59.89 ± 14.14 years old; 58.94% female) were enrolled. The weighted mean level of 25(OH)D was 59.26 ± 24.99 nmol/l and 38.95% were found with deficient (or severe deficient) vitamin D (<50.00 nmol/l). During 10453 person-years of follow-up, 268 patients were documented all-cause death, including 52 CVD deaths and 48 cancer deaths. Compared with patients with serum 25(OH)D < 25.00 nmol/l, patients with higher serum 25(OH)D were more likely to have lower rate of all-cause mortality. Nonlinear and L-shaped association between serum 25(OH)D and all-cause mortality was found, and decreased serum 25(OH)D was significantly associated with increased risk of all-cause mortality in patients with serum 25(OH)D < 37.30 nmol/l (HR 0.95 (0.92, 0.98); p < 0.01). CONCLUSION L-shaped association between serum 25(OH)D and all-cause mortality was found among patients with RA, indicating that serum 25(OH)D should be improved to a certain level for the prevention of premature death.