Active smoking, passive childhood exposure to smoking, and a history of chronic diarrhea may all significantly increase the risk of developing rheumatoid arthritis (RA), according to results from a study presented at the annual meeting of the European Congress of Rheumatology (EULAR 2017).
Researchers followed a large population of female volunteers, all born between 1925 and 1950, whom they prospectively followed since 1990 (mean duration of follow-up: 21.2 years). In all, there were 70,598 women (mean age: 49.0 years), of whom 1,239 self-reported developing RA. They included 350 cases for their analysis of the association between active and passive smoking.
Between 1990 and 2014, subjects were required to complete 11 self-administered questionnaires. The existence of RA was considered positive if women declaring RA had taken methotrexate, leflunomide, or a biologic since 2004.
In this same study, Professor Seror and colleagues also conducted a separate analysis to assess the potential association between the development of RA and a history of disrupted bowel function. For this analysis, they included 280 women.
They found that passive smoking exposure during childhood increased the association between RA risk and adult active smoking. Compared with non-smokers who were not exposed during childhood, women who were smokers and who had childhood passive exposure to smoke had a hazard ratio (HR) of 1.73. In active smokers who were not exposed to passive smoking during childhood, the HR was 1.37.
“Our study highlights the importance of avoiding any tobacco environment in children, especially in those with a family history of RA,” said lead author Professor Raphaèle Seror, University Hospitals of South Paris, France.
In addition, Dr. Seror and colleagues found that previous chronic diarrhea was associated with a more than 2-fold risk of RA (HR: 2.32), and chronic constipation or alternating between diarrhea and constipation had no impact on risk (HR: 1.16 and 1.07, respectively).
“An association between a history of chronic diarrhea and the risk of developing RA supports the hypothesis of dysbiosis (a bacterial imbalance in the gut) as a risk factor for the emergence of immune-mediated inflammatory disease,” explained Professor Seror. 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 auto-immunity, followed years later by clinical RA,” she concluded.