title: Cigarette smoking and smoking cessation in relation to risk of rheumatoid arthritis in women.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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)).
  
  
  CONCLUSIONS
  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.
authors.forename: Daniela
authors.initials: D
authors.lastname: Di Giuseppe
authors.forename: Nicola
authors.initials: N
authors.lastname: Orsini
authors.forename: Lars
authors.initials: L
authors.lastname: Alfredsson
authors.forename: Johan
authors.initials: J
authors.lastname: Askling
authors.forename: Alicja
authors.initials: A
authors.lastname: Wolk
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000453:epidemiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D016016:Proportional Hazards Models; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D016540:Smoking Cessation; D011795:Surveys and Questionnaires