TNFSF10 and rheumatoid arthritis: TRAIL partially mediated the effects of smoking initiation on RA overall, seropositive RA, and seronegative RA, with mediation effects of −0.005 (p = 0.033), −0.007 (p = 0.033), and −0.008 (p = 0.039), and mediated proportions of 1.41%, 1.80%, and 1.84% in the total effect, respectively.