Objective The aim of this study was to determine whether pollutants such as fire smoke–related particulate matter <2.5 μm (PM 2.5 ) are associated with incident rheumatoid arthritis (RA) and RA‐associated interstitial lung disease (RA‐ILD). Methods This patient–control study used Veterans Affairs (VA) data from October 1, 2009, to December 31, 2018. We identified patients with incident RA and RA‐ILD using validated algorithms, matching each patient to ≤10 controls on age, sex, and VA enrollment year. We obtained pollutants including fire smoke PM 2.5 , carbon monoxide, nitrogen oxides (NOx), ozone, overall PM 2.5 , PM 10 , and sulfur dioxide (SO 2 ) at least one year before the index date. We fit conditional logistic regression models to estimate adjusted odds ratios (aORs) with 95% confidence intervals (CIs) for incident RA and RA‐ILD, adjusted for confounders. Results We identified 9,701 patients with incident RA (mean age 65 years, 86% male), including 531 patients with RA‐ILD (mean age 69 years, 91% male), and 68,852 matched controls. Fire smoke PM 2.5 was not associated with RA (aOR 1.07, 95% CI 0.92–1.23) but was associated with RA‐ILD (aOR 1.98, 95% CI 1.08–3.62, per 1 μg/m 3 ). Increased levels of NOx were associated with RA (aOR 1.16, 95% CI 1.06–1.27, highest vs lowest quartile). The highest quartiles of ozone (aOR 1.19, 95% CI 1.06–1.34) and PM 10 (aOR 1.25, 95% CI 1.10–1.43) were associated with seronegative RA. Carbon monoxide, overall PM 2.5 , and SO 2 were not, or negatively, associated with RA and RA‐ILD. Conclusion Increased fire smoke PM 2.5 was associated with RA‐ILD, whereas NOx, ozone, and PM 10 were associated with RA risk. Thus, air pollution may increase the risk of RA and RA‐ILD. image
The Risk of Lung Cancer in Rheumatoid Arthritis and Rheumatoid Arthritis–Associated Interstitial Lung Disease
ObjectiveWe aimed to evaluate lung cancer risk in patients with rheumatoid arthritis (RA) and RA‐interstitial lung disease (ILD).MethodsWe performed a retrospective, matched cohort study of RA and RA‐ILD within the Veterans Health Administration (VA) between 2000 and 2019. Patients with RA and RA‐ILD were identified with validated administrative‐based algorithms, then matched (up to 1:10) on age, gender, and VA enrollment year to individuals without RA. Lung cancers were identified from a VA oncology database and the National Death Index. Conditional Cox regression models assessed lung cancer risk adjusting for race, ethnicity, smoking status, Agent Orange exposure, and comorbidity burden among matched individuals. Several sensitivity analyses were performed.ResultsWe matched 72,795 patients with RA with 633,937 patients without RA (mean age 63 years; 88% male). Over 4,481,323 patient‐years, 17,099 incident lung cancers occurred. RA was independently associated with an increased lung cancer risk (adjusted hazard ratio [aHR] 1.58 [95% confidence interval (CI) 1.52–1.64]), which persisted in never smokers (aHR 1.65 [95% CI 1.22–2.24]) and in those with incident RA (aHR 1.54 [95% CI 1.44–1.65]). Compared to non‐RA controls, prevalent RA‐ILD (n = 757) was more strongly associated with lung cancer risk (aHR 3.25 [95% CI 2.13–4.95]) than RA without ILD (aHR 1.57 [95% CI 1.51–1.64]). Analyses of both prevalent and incident RA‐ILD produced similar results (RA‐ILD vs non‐RA aHR 2.88 [95% CI 2.45–3.40]).ConclusionRA was associated with a >50% increased risk of lung cancer, and those with RA‐ILD represented a particularly high‐risk group with an approximate three‐fold increased risk. Increased lung cancer surveillance in RA, and especially RA‐ILD, may be a useful strategy for reducing the burden posed by the leading cause of cancer death.