Effects of short-term changes in ambient carbon monoxide on sickle cell disease hospital encounters

Symptoms of sickle cell disease (SCD) may be worsened by environmental factors. Although outdoor air pollution has been proposed as a potential trigger, the specific role of carbon monoxide (CO) among traffic-related pollutants, remains understudied in those with SCD. Based on South Carolina hospital encounter records (2002-2019) for SCD patients, we estimated daily 8-h maximum outdoor CO concentrations at patients' residential zip codes using a newly-developed spatio-temporal model. We also estimated daily particulate matter<2.5 μm (PM₂.₅), ozone (O₃), and elemental carbon (EC) concentrations using previously-developed spatio-temporal models. Using a bi-directional case-crossover design, we evaluated whether CO concentrations over 1-, 3-, 5-, 9-, and 14-day periods were associated with acute SCD hospitalizations. We also evaluated two-pollutant models adjusting for co-pollutants. We studied 8410 patients with 144,129 hospital encounters. We observed significant positive associations between EC, CO, PM_2.5, O₃ over various short-term periods with SCD hospital encounters and, among all patients and especially among children. Two-pollutant model results among children suggest CO and EC exert separate and independent effects on SCD. Exposure to short-term elevations in outdoor air pollution, especially traffic-related pollutants, may be associated with acute SCD hospitalization. These results underscore the potential health risks posed by air pollution and highlight the need for targeted interventions to reduce exposure, especially among children.