Background/Purpose: Understanding the role of environmental exposures in the development of SLE and their association with SLE activity may help identify modifiable risk factors and potential etiological mechanisms. We hypothesized that changes in coarse particulate matter (PM10, < 10 micrometers in size), sulfur dioxide, carbon monoxide, lead, and nitrogen dioxide are predictive of organ specific flares in lupus.

Methods: 1628 patients who fulfill 4 of the 11 ACR or SLICC classification criteria for SLE were included in the analysis. The data ranged from 1999 to 2017. Maximum distance between visits was 110 days with 1-month time aggregation units. Disease activity was expressed as Physician Global Estimate (PGA), taken at every patient visit. A flare was defined as a PGA score increase of 1 point or more compared to the previous visit. Environmental and atmospheric data was obtained from the EPA, including PM10, sulfur dioxide, carbon monoxide, lead, and nitrogen dioxide. The average values of each factor 10 days prior to patient visit was calculated. Univariate and multivariate models were built in order to study the association of these variables with lupus disease activity. The models were adjusted for age, sex, income, county racial distribution, rural vs. urban patient residence, distance to highways, distance to airports, PM2.5, PM10, sulfur dioxide, carbon monoxide, lead, and nitrogen dioxide concentrations, temperature, humidity, barometric pressure, ozone concentration, and residual wind. Univariate and stepwise multivariate logistic regression was used to identify significant determinants associated with lupus flares. Regression was performed for each organ flare outcome. Regression inference was based on generalized estimating equations (GEE) to account for the time repeated outcomes.

Results: Increases in sulfur dioxide concentration were directly associated with rash (p< 0.01), joints (p< 0.001), and neurologic flares (p< 0.001), and inversely associated with renal flares (p< 0.001) in multivariate analyses. Lead concentration was directly associated with neurologic (p< 0.001) and pulmonary flares (p< 0.001), and indirectly associated with serositis (p< 0.001) and renal flares (p< 0.001) in multivariate analysis. Nitrogen dioxide was directly associated with rash (p< 0.001), joints (p< 0.001), serositis (p< 0.001), hematologic (p< 0.001), pulmonary (p< 0.001), and renal flares (p< 0.001) in multivariate analysis. PM10 and carbon monoxide had no significant associations in multivariate analysis.

Conclusion: There is a strong association between changes in nitrogen dioxide, sulfur dioxide, and lead concentrations 10 days prior to patient visit and organ specific lupus activity at the visit. Nitrogen dioxide is the only pollutant with a general association with all organ specific lupus flares.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/outdoor-air-pollution-and-systemic-lupus-erythematosus/