The relationships between the SDI and the RA burdens related to smoking among the 21 GBD regions. (A) The association between the age-standardized DALY rates of RA related to smoking and SDI among 21 GBD regions. (B) The association between age-standardized death rates of RA related to smoking and SDI among 21 GBD regions. DALY: disability-adjusted life-year; GBD: global burden of disease; SDI: socio-demographic index