Passive Smoking During Childhood Significantly Increases Risk of Rheumatoid Arthritis

For the first time, new data suggest a link between passive smoking in childhood and a significant increase in the risk of rheumatoid arthritis (RA).

Additionally, preliminary results of a meta-analysis showed an association between smoking and the increased progression of structural damage to the spine in patients with ankylosing spondylitis (AS).

“Our study highlights the importance of avoiding any tobacco environment in children, especially in those with a family history of RA,” said lead author Raphaèle Seror, said in a press release.

For the study, investigators sought to analyze the impact active and passive smoking has on the risk of developing RA.

Included in the study were a large population of female volunteers born between 1925 and 1950, who were prospectively followed since 1990. The results of the study showed that passive smoking exposure during childhood increased the association between RA risk and active smoking as adults.

Smokers exposed to childhood passive smoking had a hazard ratio of 1.73 compared with non-smokers who were not exposed during childhood. The hazard ratio in active smokers not exposed to passive smoke during childhood was 1.37.

The investigators also conducted a separate analysis to evaluate the potential association between the development of RA and a history of disrupted bowel function. The results of the analysis showed that prior chronic diarrhea was associated with more than double the risk of RA, whereas chronic constipation or alternating between diarrhea and constipation had no impact on risk.

“An association between a history of chronic diarrhea and the risk of developing RA supports the hypothesis of dysbiosis as a risk factor for the emergence of immune-mediated inflammatory disease,” Seror said in a release. “These data fit perfectly with the preclinical scheme of RA where an external event occurs at an early stage to promote emergence of so-called autoimmunity, followed years later by clinical RA.”

The study included 70,598 women, of whom 1239 self-reported developing RA. There were 350 cases eligible to analyze the link to active and passive smoking, and 280 in the analysis to a history of an intestinal transit disorder. The mean age of participants was 49 years and the mean duration of follow-up was 21.2 years.

Between 1990 and 2014, 11 self-administered questionnaires were sent to the study participants to obtain medical, demographic, environmental, and hormonal data, as well as dietary habits. Two successive questionnaires collected RA diagnoses.

According to the release, passive smoking was assessed by the question: “when you were children, did you stay in a smoky room?” Patients were considered exposed if they answered, “yes a few hours,” or “yes, several hours a day.”

Intestinal transit reported by women prior to their RA diagnosis was classified as normal transit, chronic diarrhea, chronic constipation, and alternating between diarrhea and constipation.

The authors also examined whether smoking was associated with an increase in spinal damage and disease progression observed through X-rays of patients with AS.

The investigators combined data from 8 eligible studies, and found a significant association between smoking and cumulative spinal structural damage. Furthermore, studies examining the association between smoking and disease progression on spinal X-rays was reflected in new growths of syndesmophytes and/or an increase in the size of the syndesmophytes.

“Smoking constitutes a major risk factor not only for disease susceptibility but also disease severity in patients with AS,” lead author Servet Akar, said in a release. “Rheumatologist should work hard to encourage their AS patients to quit smoking as this could have a major impact on future quality of life.”

The findings were presented at the Annual European Congress of Rheumatology 2017.