June 9, 2021 — Secondhand smoke appears linked to a higher risk of rheumatoid arthritis in those who were exposed to it during childhood and adulthood, according to a new study. Though rheumatoid arthritis is not a common disease, the findings may be particularly relevant for those already at increased risk due to family history, according to the study’s lead researcher, Yann Nguyen, MD.
“Smoking is a risk factor of many diseases, including rheumatoid arthritis,” Nguyen tells WebMD. His findings, presented online June 2 at the annual European Alliance of Associations for Rheumatology (EULAR) meeting, suggest that “secondhand smoking, in childhood or in adulthood, also increases the risk of rheumatoid arthritis, and could trigger the disease at a younger age.”
Secondhand smoke has already been linked with several lung diseases and cancers, adds Nguyen, of the University of Paris-Saclay in Villejuif and
at Hospital Beaujon at the University of Paris in Clichy.
“We believe that it should be avoided as much as possible, especially among people who have an increased risk of rheumatoid arthritis, such as relatives of patients with rheumatoid arthritis,” Nguyen says.
The researchers relied on a French prospective cohort study designed to examine a/the possible link between environmental factors and chronic disease.
The study began to track 98,995 healthy French women in 1990. Most were about 49 years old.
A total of 698 women developed rheumatoid arthritis at an average 12 years after the study began.
The scientists defined exposure to secondhand smoke in childhood as spending several hours a day in a smoky room.
Secondhand smoke exposure in adulthood was defined as spending at least 1 hour per day around actively smoking adults.
About 1 in 7 of the women (13.5%) reported exposure to cigarette smoke as children, and just over half (53.6%) reported being exposed to smoking as adults. An overall 58.9% had secondhand exposure in adulthood or childhood, and 8.25% had both.
After taking into account differences between the women’s body mass index (BMI) and educational level, risk of rheumatoid arthritis was 1.4 times greater for women who never smoked but had childhood secondhand smoke exposure. Their risk was 1.3 times greater for women who never smoked but reported regularly being around secondhand smoke as adults.
Participants who currently smoke or used to smoke did not have a greater rheumatoid arthritis risk based on their secondhand smoke exposure. However, the risk of developing the disease was greater for these women based on their history of smoking alone.“Secondhand smoking in childhood, as well as active smoking, seem to increase the odds of having rheumatoid arthritis later in life,” says Loreto Carmona, professor and chair of the European Alliance of Associations for Rheumatology scientific program committee and scientific director of the Institute for Musculoskeletal Health in Madrid. “Preventive measures for rheumatoid arthritis should include avoiding smoking and also doing it in front of children. This study supports advocacy for smoke-free environments.”
Hendrik Schulze-Koops, MD, head of the Division of Rheumatology at Ludwig-Maximilians-University of Munich in Germany, agrees that these findings send an important message to those who currently smoke around children.
“Children should be spared from passive smoking,” Schulze-Koops says. “This is necessary with respect to many aspects of their health, the latest now being the risk for developing rheumatoid arthritis.”
Though the study was unable to show that secondhand smoke played a role in causing rheumatoid arthritis in the women who developed it, previous research has determined “a direct effect of active cigarette smoking on the development of autoimmunity leading to rheumatoid arthritis,” says Nguyen, noting a direct link in this case is possible.
That said, rheumatoid arthritis is a rare disease, affecting approximately 30 out of 100,000 people per year, Nguyen says.
This study was unable to show that secondhand smoke played a role in causing rheumatoid arthritis in the women who developed it, but previous research has shown “a direct effect of active cigarette smoking on the development of autoimmunity leading to rheumatoid arthritis,” Nguyen says, so they believe a direct link in this case is possible as well.
That said, he noted that rheumatoid arthritis is a rare disease, affecting approximately 30 out of 100,000 people per year.
“Very few nonsmokers exposed to passive smoking will develop rheumatoid arthritis,” Nguyen says. “This is why we believe that such exposure should be limited, especially among people at risk of rheumatoid arthritis.”
Still, limiting secondhand smoke exposure to everyone, particularly children, could help to prevent other diseases, he adds.
“Rheumatoid arthritis is not the only consequence of passive smoking and — as severe as it might be — probably not the most dramatic, but it is bad enough to avoid risks wherever possible,” Schulze-Koops says. “Passive smoking is avoidable. Do not get your children in a situation where they are exposed.”