Smoking associated with reduced odds of Sjögren's syndrome among rheumatoid arthritis patients

The objective of this medical record review study is to define the association between smoking and Sjӧgren's syndrome (SS) in a large rheumatoid arthritis (RA) cohort.

Electronic health records from a population-based cohort were screened for RA eligibility between 2005 and 2018. Inclusion criteria were age ≥ 18 years, two or more RA diagnoses, including two diagnoses by a rheumatologist, or positive rheumatoid factor or anti-cyclic citrullinated peptide (anti-CCP) antibody. The independent variable, smoking status, was defined as never, current, or past. The outcome, SS, was defined by two or more ICD-9 codes. Multivariable logistic regression was performed to determine odds ratios (ORs) of SS adjusted for age, sex, and race.

Among 1861 patients with RA identified for cohort inclusion, 1296 had a reported smoking status. Current smokers were younger and less likely to be female than never smokers. The adjusted OR of current compared to never smokers was negatively associated with SS [OR 0.20, 95% confidence interval (CI) 0.06-0.65]. Female sex and age were associated with SS (OR 2.70, 95% CI 1.18-6.14; OR 3.75, 95% CI 1.23-11.4).

We report that RA patients who currently smoke had 80% lower odds of SS. Age had a 3.7-fold association and female sex a 2.7-fold association with SS among RA patients. Our data suggest a negative correlation between current smoking and prevalent SS among RA patients. Prospective studies examining pack-year relationships or smoking cessation could further examine risk reduction and causality to follow-up our cross-sectional observational study.