A Spatial-Temporal Analysis of Organ-Specific Lupus Flares in Relation to Fine Particulate Matter Pollution and Temperature

Abstract

Objectives: We performed a spatial-time cluster analysis of the Hopkins Lupus Cohort with the goal of identifying potential clusters of SLE organ specific flares and their relation to temperature changes and fine particulate matter pollution (PM2.5). Methods: 1261 patients who fulfilled the SLICC classification criteria for SLE and who had recorded home addresses were included in the analysis. Disease activity was expressed as the Lupus Activity Index. Assessment of rash, joint involvement, serositis, neurologic, pulmonary, renal, and hematologic activity was quantified on a 0-3 VAS. An organ specific flare was defined as an increase in visual analogue scale (VAS) of 1 point or more compared to the previous visit. Average temperature and PM2.5 exposure over a period of 10 days prior to patient visit were obtained. Spatiotemporal cluster detection was conducted using the SaTScan software. Regression models were used for adjustment and included age, sex, and race, as well as PM2.5 and temperature. Results: Three statistically significant (p<0.05) unadjusted clusters were identified for joint flares, four rash flare clusters, one hematologic flare cluster, four neurologic flare clusters, three serositis flare clusters, four renal flare clusters, and five pulmonary flare clusters. Most of the identified clusters changed in significance, temporal, or spatial extent after adjusting for temperature, PM2.5 concentration, and individual covariates. Conclusions: We describe the first space-time clusters of lupus organ-specific disease activity. Seasonal, as well as multi-year cluster patterns were identified, differing in extent and location for the various organ-specific flare types. Further study focusing on each individual lupus organ-specific activity will be required to better understand the driving forces behind these observed changes. Funding Statement: The Hopkins Lupus Cohort is supported by a grant from the National Institute of Health (NIH AR 43727 and 69572). This publication was also made possible by Grant Number UL1 RR 025005 from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH), and NIH Roadmap for Medical Research. Dr. George Stojan is a Jerome L. Greene Foundation Scholar. Dr. Frank Curriero is supported by NIH grant R01AI123931. Declaration of Interests: The authors state: None. Ethics Approval Statement: The Hopkins Lupus Cohort has been approved by the Johns Hopkins University School of Medicine Institutional Review Board and complies with the Health Insurance Portability and Accountability Act.