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Childhood Secondhand Smoke Exposure may Increase Adult RA Risk
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Exposure to secondhand smoke during childhood may increase the risk for rheumatoid arthritis as an adult among patients who later become light smokers — and potentially those who never become smokers — according to findings published in Rheumatology.
“To date, smoking is the only conventional environmental factor that has reproducibly been linked to an increased risk of developing RA,” Marie-Christine Boutron-Ruault, PhD, of Institut Gustave Roussy in Villejuif, France, and colleagues wrote. “However, to date, limited data focus on the potential role of passive smoking in triggering RA, and no data exist on early exposure to tobacco (ie, during childhood) and the risk of developing RA.”
To determine the association between smoking — including secondhand exposure during childhood and as an adult — and the risk for RA, Boutron-Ruault and colleagues studied data from the French Etude Epidémiologique auprès de femmes de la Mutuelle Générale de l’Education Nationale (E3N) cohort. According to the researchers, E3N is a general-population cohort that was formed to analyze risk factors associated with cancer and other major non-communicable diseases in women, and includes 98,995 participants born between 1925 and 1950 who were insured under the national health system that largely covers teachers, co-workers and their partners.
All participants in the E3N cohort received self-administered questionnaires every 2 to 3 years, which collected data on medical events, general lifestyle and environmental characteristics. The researchers identified patients with RA through three successive questionnaires, and later confirmed the diagnoses via reimbursement data for RA-specific medication. After excluding prevalent cases, as well as those without a date, follow-up information or data on smoking status, Boutron-Ruault and colleagues focused their research on 71,258 women in the E3N. Risk for RA was calculated using an age-adjusted Cox model.
According to the researchers, there were 371 confirmed cases of RA. Among participants who never smoked, secondhand exposure during childhood was associated with a “borderline increased risk” for RA (HR = 1.43; 95% CI, 0.97-2.11). This placed them in the same range as adults who were active smokers, the researchers wrote. Participants who smoked at any point, but were not exposed to secondhand smoke, also demonstrated an increased risk for RA (HR = 1.38; 95% CI, 1.1-1.74).
Ever-smokers with childhood exposure to secondhand smoke had a higher risk for RA than smokers who were never exposed during childhood (HR = 1.67; 95% CI, 1.17-2.39), but without a significant difference (P = 0.3). Lastly, RA began earlier among smokers exposed to childhood secondhand smoke, the researchers wrote.
“Our findings perfectly fit with the preclinical scheme of RA where an external event occurs at an early stage to promote emergence of autoimmunity, followed years after by clinical RA,” Boutron-Ruault and colleagues wrote. “As demonstrated for many other risks, our results highlight the importance of protecting children from any environmental tobacco smoke exposure, especially in those with a family history of RA. If the current regulation of smoking has certainly reduced exposure in public places, passive exposure at home is under the responsibility of parents that must be aware of such a risk.” – by Jason Laday
Disclosure: Boutron-Ruault reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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