Smoking tied to higher disease activity in RA
An association exists between smoking and higher levels of disease activity in rheumatoid arthritis (RA), suggests a new study.
Compared with nonsmoking, smoking correlated with a 0.64-unit increase in the patient global score (p=0.01) and with 2.58 more swollen joints (p<0.001). Smoking was also associated with a higher clinical disease activity score (2.11), but the difference was statistically nonsignificant (p=0.22).
On the other hand, there was no association between smoking and physician global score or C-reactive protein levels, but an inverse interaction was found between smoking and tender joint count (p=0.05). Furthermore, there was a null relationship for all outcomes in analyses using conventional methods.
“Causal methods may be useful for investigations of additional exposures on longitudinal outcome measures in rheumatologic disease,” the authors said.
This study examined the link between smoking and RA outcomes using statistical methods that accounted for time-varying confounding and loss to follow-up. Electronic health record data collected at a public hospital between 2013 and 2017 were used to identify 282 individuals with an RA diagnosis.
The authors evaluated current smoking status and disease activity at each visit, including sex, race/ethnicity, age, obesity and medication use as covariates. They calculated the causal effect of smoking on disease activity measures at 27 months using longitudinal targeted maximum likelihood estimation and compared results to conventional longitudinal methods.
“Prior studies around the relationship between smoking and RA disease activity have reported inconsistent findings, which may be ascribed to heterogeneous study designs or biases in statistical analyses,” the authors noted.