Cigarette smoking and smoking cessation in relation to risk of rheumatoid arthritis in women
1 Division of Nutritional Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Nobels vag 13, Stockholm, 171 77, Sweden
2 Division of Cardiovascular Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Nobels vag 13, Stockholm, 171 77, Sweden
3 Clinical Epidemiology Unit, Department of Medicine, Rheumatology Unit d2:01, Karolinska University Hospital, Solna, 171 76, Sweden
Arthritis Research & Therapy 2013, 15:R56 doi:10.1186/ar4218Published: 22 April 2013
Whereas the overall association between smoking and rheumatoid arthritis (RA) must be regarded as established, considerably less is known about how much smoking is needed to increase the risk of RA, that is, the effect of smoking intensity, duration and cessation.
The Swedish Mammography Cohort, including 34,101 women aged 54 to 89 years, was followed up from January 1, 2003 through December 31, 2010 (219 RA cases identified). Relative risks (RR) and their 95% confidence intervals (CI) were estimated as rate ratios using Cox proportional hazards model.
There was a statistically significant association between smoking intensity (RR comparing 1 to 7 cigarettes/day vs never smoking 2.31 (95% CI: 1.59, 3.36)) as well as duration of smoking (comparing 1 to 25 years vs never smoking RR = 1.60 (95% CI: 1.07, 2.38)) and risk of RA. Compared to never smokers, the risk was still significantly elevated 15 years after smoking cessation (RR = 1.99 (95% CI: 1.23, 3.20)). However, among former smokers, the risk of RA seemed to be decreasing over time since stopping smoking: women who stopped smoking 15 years before the start of the follow-up had 30% lower risk of RA compared to those who stopped only a year before start of the follow-up (RR = 0.70 (95% CI: 0.24,2.02)).
This prospective study highlights that even light cigarette smoking is associated with increased risk of RA in women and that smoking cessation may reduce, though not remove, this risk.