Table 2.

List of the seven studies with the confounders that were included in the adjusted analysis.

Author	Confounders assessed
Chung WS, Lin CL	Sex, age, comorbidities (hypertension, diabetes, CVA, heart failure, all cancer, pregnancy, atrial fibrillation, lower leg fracture of surgery, asthma, CAD, COPD, RA, obesity)
Ahlehoff O, Gislason GH, Lindhardsen J, et al.	Age, malignancy, surgery, rheumatological disease
Lutsey PL, Prizment AE, Folsom AR	Age, education, smoking status, BMI, DM, HRT use
Ogdie A, McGill NK, Shin DB, et al.	joint replacement surgery, malignancy, heart of respiratory failure, pregnancy, hormone therapy, smoking, alcohol intake, BMI, hospitalization during the baseline period, year of cohort entry, socioeconomic status, urban versus rural living environment, Charlson comorbidity score, chronic kidney disease, myocardial infarction, atrial fibrillation, diabetes, hypertension, COPD, liver disease, disability status, start year in the cohort and interaction between disease status and DMARD use
Ramagopalan SV, Wotton CJ, Handel AE, et al.	Age, sex, region of residence
Zöller B, Li X, Sundquist J, et al.	Sex, age, hospitalization, COPD, obesity, alcohol use, CAD, stroke, hypertension, varicose vein, sepsis, CHF, PVD
Yen YC, Weng SF, Lai FJ, et al.	Sex, age, comorbidities (DM, HTN, CHD, hyperlipidaemia, obesity and COPD)