Arundathi Jayatilleke, MD
Cigarette smoking is a well-known modifiable risk factor for the development of rheumatoid arthritis (RA). Studies have suggested not only an elevated risk but possible pathogenetic role in the development of autoantibodies, as well as effects on disease outcomes. Passive cigarette smoking has also been proposed as a potential risk factor for RA, though studies are harder to evaluate. This review of prospective data from the Nurses Health Study (NHS) by Yoshida et al looks at incident RA among women enrolled in the study and the influence of in utero , childhood, and adulthood exposure to cigarettes. Childhood exposure to parental smoking was associated with seropositive RA (hazard ratio 1.75) even after controlling for adult personal smoking, and maternal smoking during pregnancy was associated with RA, though the latter effect was not seen after controlling for subsequent smoking exposure. As the authors point out, verifiable prospective data is difficult to obtain regarding exposure to smoking in utero or in childhood and recall bias is possible in obtaining historical information in this prospective study given the use of questionnaires, though it remains plausible given prior studies on the association of personal smoking with RA.
The involvement of gut microbiota in development of autoimmunity has also been postulated but not well-explained. Several recent studies have examined the impact of antibiotic use on the development of RA, including a recent large UK-based case-control study suggesting an increase in RA incidence in people with antibiotic exposure. While a systematic review is ongoing, this prospective cohort study by Liu et al also examines data from NHSI and NHSII and RA risk in patients exposed to antibiotics, stratified by duration of use (none, ≤14 days, ≥15 days). It is reassuring that in this study neither short term (≤14 days) nor long term (≥15 days) antibiotic use was associated with RA risk. Comparison with prior studies with prescription data, however, is limited given the use of questionnaires to establish duration of recent antibiotic exposure.
Fatigue is a common symptom of RA and has a high impact on quality of life in terms of function. The study by Holten et al examines data from the ARCTIC trial in terms of associations between disease activity and fatigue in early RA, as well as change in fatigue with therapy for RA. Fatigue was measured via a visual analog scale (VAS) and did decrease with therapy from baseline; 80% of patients in the study had moderate or high disease activity based on disease activity score (DAS) at baseline and 69% of patients reported fatigue, while 9% of patients had moderate or high disease activity based on DAS at 24 months and 38% reported fatigue. Interestingly, patients who were in remission (per DAS) at 6 months had a reduced risk of fatigue at 24 months. It is hard to interpret this information in a granular way as fatigue is not measured in a standardized way across clinical studies and the only instrument of measure in the ARCTIC trial was the VAS. An alternate view, for example examining the impact of baseline fatigue on response to therapy, may also be reasonable, or fatigue may be a residual symptom similar to chronic myofascial or “non-inflammatory” pain not responsive to treatment in RA.
Finally, another associated extra-articular manifestation of RA is bronchiectasis. Martin et al performed a systematic review and meta-analysis of the literature and found that the prevalence of bronchiectasis was about 18% in RA patients, suggesting that it is more common than previously thought. However, inclusion of CT imaging may detect subclinical bronchiectasis and other secondary causes were not determined. Still, given the effects on quality of life and mortality, further research into causes and risk factors for bronchiectasis in RA is warranted.