Study data published in Arthritis Care & Research demonstrated that sustained smoking cessation could delay or even prevent the onset of seropositive rheumatoid arthritis (RA).
Investigators abstracted data from the Nurses’ Health Study (NHS; 1976-2014) and the NHSII (1989-2015), prospective cohort studies of registered female nurses in the United States. The NHS enrolled 121,700 nurses aged 30 to 55 years; the NHSII enrolled 116,430 nurses aged 25 to42 years. Participants completed baseline and biennial questionnaires on lifestyle and health behaviors during the study course; each cohort had a >90% response rate over the study course. Detailed information on smoking exposures and covariates were extracted from the self-report questionnaires.
Additionally, self-reported RA was confirmed by medical record review by 2 rheumatologists. Patients who met the 1987 American College of Rheumatology (ACR) or 2010 ACR/European League Against Rheumatism RA classification criteria were considered RA cases. Data from the NHS and NHSII were pooled into a single analysis, and Cox proportional hazards models were used to test the association between RA risk by phenotype and smoking status. The final analyses excluded participants who did not provide smoking data and those who reported RA or other connective tissue diseases at baseline.
The final cohort comprised 117,182 women in the NHS (1976-2014) and 113,550 women in the NHSII (1989-2015) for 6,037,151 person-years of follow-up. A total of 1528 incident RA cases were identified during follow-up, among which 969 (63.4%) were seropositive and 559 (36.6%) were seronegative. The NHS had a greater proportion of smokers (18.8% current smokers, 35.8% past smokers) compared with the NHSII (13.4% current smokers, 21.3% past smokers).
RA was more likely to develop in both past smokers (adjusted hazard ratio [aHR], 1.36; 95% CI, 1.22-1.53) and current smokers (aHR, 1.46; 95% CI, 1.26-1.70) compared with women who never smoked, even after adjustments for age, questionnaire period, cohort, oral contraceptive use, parity/breastfeeding, menopausal status, body mass index, sedentary physical activity, median household income, and alcohol intake.
According to cubic spline curves comparing RA and smoking cessation, risk for RA developing decreased with increasing years since smoking cessation for both all RA (P =.009) and seropositive RA (P =.002). The same trend was not observed for seronegative RA, however (P =.78). Women who quit smoking ≥30 years ago had a suggestive reduced risk for all RA (HR, 0.78; 95% CI, 0.58-1.05) and a significantly reduced risk for seropositive RA (HR, 0.63; 95% CI, 0.44-0.90) compared with those who quit 0 to <5 years ago.
These data underscore a significant association between smoking and risk for RA, particularly in current smokers with high intensity or past smokers with many pack-years. The risk for seropositive RA was significantly reduced in past smokers by time since smoking cessation, suggesting that smoking cessation may decrease or even prevent the onset of RA. Further research is necessary to elucidate the precise mechanisms behind this relationship.
Liu X, Tedeschi SK, Barbhaiya M, et al. Impact and timing of smoking cessation on reducing risk for rheumatoid arthritis among women in the Nurses’ Health Studies [published online February 21, 2019]. Arthritis Care Res. doi:10.1002/acr.23837