WEDNESDAY, Aug. 18, 2021 (HealthDay News) — Childhood exposure to parental smoking is associated with a greater risk for adult-onset incident rheumatoid arthritis (RA) even after controlling for a personal smoking habit as an adult, according to a study published online Aug. 18 in Arthritis & Rheumatology.

Kazuki Yoshida, M.D., Sc.D., from Brigham and Women’s Hospital in Boston, and colleagues used data from the Nurses’ Health Study II prospective cohort to examine passive smoking throughout the life course and the risk for RA among 90,923 women.

The researchers identified 532 incident RA cases during 27.7 years of follow-up. After adjustment for confounding variables, maternal smoking during pregnancy was associated with RA (hazard ratio, 1.25), but not after accounting for subsequent smoking exposures. After adjustment for confounders, childhood parental smoking was associated with seropositive RA (hazard ratio, 1.41). Childhood parental smoking was associated with seropositive RA in the controlled direct effect analyses (hazard ratio, 1.75) after controlling for adult personal smoking, with a stronger association noted among ever smokers (hazard ratio, 2.18). No significant association was seen for adult passive smoking with RA.

“Our observations are most compatible with the ‘cumulative exposure’ model in life-course epidemiology, in which both childhood parental smoking and later-life personal smoking increase the risk of adult incident seropositive RA,” the authors write. “In particular, childhood passive smoking may be a risk factor that further amplifies the influence of adult personal smoking.”

Two authors disclosed financial ties to the biopharmaceutical industry.

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