Among patients with systemic lupus erythematosus, rash, joint involvement and flares are positively linked with fine particulate matter pollution, according to a spatial-time cluster analysis published in Arthritis & Rheumatology.
“Fine particulate matter pollution (PM2.5) averaged for up to 10 days prior to the patient visit was associated with anti-dsDNA and cellular casts but not with global disease activity in a Montreal lupus cohort,” George Stojan, MD, of Johns Hopkins University, and colleagues wrote. “A population-based cohort study from Taiwan showed a positive association between a 10.2g/m3 increase in fine particulate matter concentration and new diagnoses of SLE. Similarly, population-based studies from Alberta and Quebec showed that PM2.5 exposure may be associated with an increased risk of systemic autoimmune diseases, including SLE.”
To identify potential clusters of organ-specific flares, and their relations to temperature changes and PM2.5, among patients with SLE, Stojan and colleagues conducted a space-time cluster analysis of participants in the Hopkins Lupus Cohort. Stojan and colleagues included 1,261 patients who fulfilled the Systemic Lupus Erythematosus International Collaborating Clinics (SLICC) criteria for SLE and a recorded home address.
The researchers expressed disease activity using the Lupus Activity Index. In addition, they assessed rashes and joint involvement and serositis, as well as neurologic, pulmonary, renal, and hematologic activity using a 0 to 3 visual analogue scale. Organ-specific flares were defined as an increase of 1 or more on the visual analogue scale, compared with the previous visit. SaTScan software was used to detect spatialtime clusters, and regression models were performed for cluster adjustment for individual, county-level and environmental variables.
Among patients with SLE, rash, joint involvement and flares are positively linked with fine particulate matter pollution, according to a spatial-time cluster analysis.
According to the researchers, the univariate regression analysis demonstrated that rash and joint flares were positively associated (P < .05) with PM2.5, while serositis was marginally associated (P = .053). Rash (OR = 1.065), joint (OR = 1.047) and hematologic (OR = 1.095) flares were significantly positively associated with temperature changes, while renal flares (OR = 0.96) demonstrated a marginally (P = .072) negative link.
In addition, ozone concentration was associated (P < .05) with rash (OR = 1.013), but negatively associated with renal flares (OR = 0.992). Resultant wind was positively associated (P < .05) with joint (OR = 1.039), neurologic (OR=1.099), renal (OR = 1.028) and pulmonary (OR = 1.135) flares. Relative humidity was associated (P < .05) with joint involvement (OR = 1.163), and marginally (P = .077) linked with neurologic (OR = 1.099) flares.
In addition, the researchers found three statistically significant (P < .05) special-time clusters — all unadjusted for environmental variables — for joint flares, as well as four rash flare clusters (P < .05), three hematologic flare clusters (P < .05), two neurologic flare clusters (P < .05), four renal flare clusters (p < .001), two serositis clusters (P < .001) and two pulmonary flare clusters (P < .001). Most of these clusters changed in significance, or in temporal or spatial extent, after adjusting for environmental variables, including fine particulate matter pollution, temperature, ozone, resultant wind, barometric pressure and relative humidity.
“Seasonal, as well as multi-year cluster patterns were identified, differing in extent and location for the various organ-specific flare types,” Stojan told Healio Rheumatology. “The large-scale, multi-year clusters we defined did not conform to any known pattern of infectious disease or environmental exposure.”
“Spatial and temporal clustering of organ-specific lupus flares raises the concern for potential environmental hazards as triggering factors and raises hope that we might be able to identify these factors in the future, and even predict when and where flare clusters will occur,” he added. “The proposed spatial temporal analytical methods could thus lay the foundation for a new approach in the discovery of potential environmental and atmospheric factors and their role in lupus.” – by Jason Laday
Disclosure: The researchers report no relevant financial disclosures.