A photo of a mother carrying a child, scolding a father who is holding a cigarette.
Credit: Jikaboom/iStock

Although doctors don’t know the exact cause of rheumatoid arthritis (RA), they do know certain risk factors — such as genetics and family history — can increase your chances of developing the disease. Smoking is also a known risk factor for developing RA — and the risk isn’t limited to active smokers (people who currently smoke at least on cigarette a day.)

According to a new study, being exposed to smoking as a child (passive smoking) can increase your chances of developing RA later in life.

For the study, which was published in the journal Arthritis & Rheumatology, researchers used data available from the Nurses’ Health Study II (NHSII) to examine the relationship between exposure to passive smoking and the development of RA. The data included information from 90,923 women, which was collected every two years from 1989 to 2017 via a questionnaire.

Researchers used medical records to determine which patients had a confirmed rheumatoid arthritis diagnosis. They also assessed whether patients had seronegative or seropositive RA, meaning their blood has antibodies that can attack the body and inflame the joints. Of the 90,923 participants, 532 had confirmed RA cases (352 were seropositive and 180 were seronegative).

Using a questionnaire, researchers gained insight into the smoking exposure of patients. There were three passive smoking exposures of interest:

  • Maternal smoking during pregnancy (in utero exposure)
  • Parental smoking during childhood (childhood exposure)
  • Adult passive smoking (adult exposure)

Maternal and parental smoking was determined based on a “yes” or “no” response. For adult passive smoking, patients were asked to determine the number of years they lived with a household smoker since turning 18. Researchers also asked patients about their personal smoking habits.

According to the study, childhood exposure to smoking increased a person’s risk of developing seropositive RA by 75 percent. The risk was even higher among patients who were exposed to smoking during childhood and then began smoking themselves later in life.

Researchers did not find a link between RA development and in utero exposure or adult exposure to smoking.

“Since maternal smoking during pregnancy affects the fetus through placental transfer and not through direct inhalation, this may also explain some of the differences of this passive smoking exposure compared to the others,” researchers wrote.

Though the study reveals some interesting initial insights into the link between smoke exposure and RA development, there were some limitations that need to be addressed in future studies. Some examples include the inability to assess early-life RA cases and male RA patients.

“Our findings give more depth and gravity to the negative health consequences of smoking in relation to RA,” says lead and co-corresponding author Kazuki Yoshida, MD, ScD, of the Brigham’s Division of Rheumatology, Inflammation, and Immunity. “This relationship between childhood parental smoking and adult-onset RA may go beyond rheumatology — future studies should investigate whether childhood exposure to inhalants may predispose individuals to general autoimmunity later in life.”

Although more research is needed, this study is an important reminder of the risks smoking exposure can have on children’s future health.

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Brigham and Women’s Hospital. Smoking exposure during childhood may increase risk of rheumatoid arthritis. Medical XPress. August 18, 2021. https://medicalxpress.com/news/2021-08-exposure-childhood-rheumatoid-arthritis.html.

Yoshida K, et al. Passive Smoking Throughout the Life Course and the Risk of Incident Rheumatoid Arthritis in Adulthood Among Women. Arthritis & Rheumatology. August 18, 20201. doi: https://doi.org/10.1002/art.41939.

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