Background: People living with sickle cell disease (SCD), a rare genetic disorder, may be uniquely vulnerable and susceptible to inflammatory-mediated illnesses from exposure to wildfire smoke. Although the frequency and severity of wildfires are increasing, no studies to our knowledge have looked at associations between wildfire smoke and emergency department (ED) visits among people with SCD.

Methods: We conducted a time-stratified case-crossover study assessing the relationships between wildfire smoke and ED visits among children with SCD living in California from January 2006 to December 2019. Children with SCD and ED visits were identified using California’s Sickle Cell Data Collection population-based cohort. Daily mean wildfire and total fine particulate matter (PM2.5) and total ozone (O3) concentrations at lags1-3 were estimated using an ensemble machine learning model and assigned by children’s residential ZIP code at time of ED visit. Conditional logistic regression models, adjusted for meteorological factors, were used to quantify the exposure-outcome relationship.

Results: We identified 589 children, 276 children, and 31 children with at least one eligible ED visit for all-causes, pain, and acute chest syndrome (ACS), respectively. Consistent with prior literature, we found PM2.5 at lag3 most predictive of ED visits. A 1 μg/m3 increase in total PM2.5 was associated with higher odds of ED visits for ACS (OR=1.119; 95%CI=1.005, 1.245). Wildfire PM2.5 was also associated with higher odds of ED visits for ACS (OR=1.072; 95%CI=0.968, 1.187), pain (OR=1.004; 95%CI=0.982, 1.028), and all-causes (OR=1.002; 95%CI: 0.991, 1.013) per 1 μg/m3 increase, but these changes were not statistically significant.

Conclusion: Total PM2.5 was associated with increased odds of ED visits for ACS among children with SCD in California from 2006 to 2019. More research is needed to identify patterns of vulnerability and susceptibility to wildfire smoke among children with SCD.