MADRID – Second-hand smoke exposure to children was about as potent a trigger for future rheumatoid arthritis as active smoking by an adult, based on an analysis of data collected from more than 70,000 French women followed for an average of more than 20 years
“This is the first demonstration of a rheumatoid arthritis risk associated with passive smoking,”
“This is an important finding because we can avoid passive smoke exposure,” Dr. Seror added in a . The imperative to eliminate second-hand smoke exposure to children is particularly acute for those with a genetic risk for developing rheumatoid arthritis (RA), specifically children with a parent diagnosed with RA, suggested Dr. Seror, a professor of rheumatology at the University of Paris–South.
She and her associates used data collected in the , a longitudinal French epidemiological study that enrolled nearly 100,000 women in 1990 when they were 40-65 years old and collected health data by questionnaire every 2-3 years for an average of 21 years. They identified from this cohort women with “confirmed” RA based on a self report of having incident RA during follow-up plus a coincident record of reimbursement for a prescription for an RA-specific treatment, such as methotrexate or a biological disease-modifying drug.
This identified 389 women with confirmed incident RA, including 350 with a complete smoking history that made the current analysis possible. The study also included 70,248 women who did not develop RA and who had provided a complete smoking history.
The analysis showed that women who reported a history of second-hand smoke exposure estimated at more than an hour daily as children but without a history of active smoking had a 43% higher rate of incident RA compared with never smoker women without a history of passive smoke exposure, Dr. Seror . This association just missed reaching statistical significance, a limitation that Dr. Seror attributed to a power issue as the analysis included only 30 women who had incident RA and a history of second-hand smoke exposure without adult smoke exposure. By comparison, women in the study with a history of active smoking without childhood exposure linked had a 37% increased incidence of RA, a finding that confirmed the well-known link between smoking and RA incidence.
The study also found that women with both second-hand smoke exposure as children and adult smoking linked with a 73% higher RA incidence, an indication that the contributions from second-hand smoke in children and active smoking by adults were not only similar in magnitude but also worked additively to promote RA development.