Associations between Ambient Fine Particulate Levels and Disease Activity in Patients with Systemic Lupus Erythematosus (SLE)

BACKGROUND: Systemic lupus erythematosus (SLE) is a chronic disease of unclear etiology, characterized by an overactive immune system and the production of antibodies that may target normal tissues of many organ systems, including the kidneys. It can arise at any age and occurs mainly in women. OBJECTIVE: Our aim was to evaluate the potential influence of particulate matter (PM) air pollution on clinical aspects of SLE. Methods: We studied a clinic cohort of SLE patients living on the island of Montreal, followed annually with a structured clinical assessment. We assessed the association between ambient levels of fine PM [median aerodynamic diameter <= 2.5 mu m (PM2.5)] measured at fixed-site monitoring stations and SLE disease activity measured with the SLE Disease Activity Index, version 2000 (SLEDAI-2K), which includes anti-double-stranded DNA (anti-dsDNA) serum-specific auto-antibodies and renal tubule cellular casts in urine, which reflects serious renal inflammation. We used mixed effects regression models that we adjusted for daily ambient temperatures and ozone levels. RESULTS: We assessed 237 patients (223 women) who together had 1,083 clinic visits from 2000 through 2007 (mean age at time of first visit, 41.2 years). PM2.5 levels were associated with anti-dsDNA and cellular casts. The crude and adjusted odds ratios (reflecting a 10-mu g/m(3) increase in PM2.5 averaged over the 48 hr prior to clinical assessment) were 1.26 [95% confidence interval (CI), 0.96-1.65] and 1.34 (95% CI, 1.02-1.77) for anti-dsDNA antibodies and 1.43 (95% CI, 1.05-1.95) and 1.28 (0.92-1.80) for cellular casts. The total SLEDAI-2K scores were not associated with PM2.5 levels. CONCLUSIONS: We provide novel data that suggest that short-term variations in air pollution may influence disease activity in established autoimmune rheumatic disease in humans. Our results add weight to concerns that pollution may be an important trigger of inflammation and autoimmunity.