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Smoking associated with increased risk for RA among women; cessation decreased risk
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Even women who were considered light smokers had an increased risk for developing rheumatoid arthritis compared with never smokers, although that risk decreased over time among those who quit, according to recent study results.
In a population-based, prospective study, Daniela Di Giuseppe, a PhD student in the Division of Nutritional Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, and colleagues reviewed the Swedish Mammography Cohort, which included 34,101 women aged 54 to 89 years who were followed from 2003 to 2010. Researchers identified 219 cases of rheumatoid arthritis (RA) by linking the cohort to three Swedish registers. Cox proportional hazard model was used to estimate association between smoking and RA. Data from a 1997 questionnaire sent to the cohort, which included smoking status, number of cigarettes smoked per day at different ages, age of starting and years since stopping smoking, were used.
Daniela Di Giuseppe
Of the RA patients, 36% were never smokers, 27% were former smokers and 37% currently smoked. RA risk had a statistically significant association with smoking intensity (comparing one to seven cigarettes a day [light smoking] vs. never smoking (RR=2.31; 95% CI, 1.59-3.36) and smoking duration (1 to 25 years vs. never smoking, RR=1.60; 95% CI, 1.07-2.38).
Women who had stopped smoking 15 years earlier still had an elevated risk for RA (RR=1.99; 95% CI, 1.23-3.20) compared with never smokers, but among former smokers the risk for RA appeared to decrease after cessation. There was a 30% reduced risk for developing RA among those who quit smoking 15 years before the start of follow-up vs. those who stopped 1 year before follow-up (RR=0.70; 95% CI, 0.24-2.02).
“Our study indicated that even light smoking is associated with increased risk of RA for women,” the researchers concluded. “In extension to this, we showed that the risk of RA was decreasing over time after smoking cessation, but compared to never smokers the risk was still statistically significantly higher. The clearly increased risk of RA development even among former smokers is another reason to persuade women not to start smoking.”
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