Medi-Cal Data Reveals the Public Health Impact of a Large Wildfire Event

BACKGROUND:  Wildfire-derived particulate matter has been linked to adverse respiratory outcomes and, in some studies, cardiovascular outcomes. Children, the elderly, and persons with chronic respiratory conditions are considered to be at increased risk. Impacts beyond mortality, hospitalization and emergency department visits have seldom been studied. This study characterizes the impact of the 2007 San Diego Firestorm, in which 500,000 residents evacuated and millions were exposed to smoke, on beneficiaries of Medi-Cal, the Medicaid program serving low-income Californians, including a high proportion of children.

METHODS:  Episodes of care and associated respiratory and cardiovascular ICD-9 codes were identified from Medi-Cal claims records. In addition to overall emergency department visits, inpatient hospitalizations, and outpatient visits to doctor’s offices and clinics, we analyzed visits by diagnosis. A respiratory index included asthma, acute bronchitis, COPD, pneumonia, upper respiratory infections, and respiratory symptoms; a cardiovascular index included ischemic heart disease, dysrhythmias, chronic heart failure, cerebrovascular disease, and peripheral vascular disease. A five-day county-wide exposed period was defined based on modeled air quality data. We calculated rate ratios (RR), comparing encounters in the exposed period to reference periods from preceding weeks.

RESULTS:  During the fire period, emergency department visits from all causes were equal to reference periods (RR=1.00, 95% CI 0.94-1.07), those for respiratory diagnoses increased by 28% (95% CI 13-44%), and those for asthma increased by 95% (95% CI 46-160%), while those for cardiovascular diagnoses were unchanged (RR=0.91, 95% CI 0.68-1.22). Office and clinic visits decreased by 31% (95% CI 30-33%), those for respiratory diagnoses were unchanged (RR=0.99, 95% CI 0.94-1.04), those for asthma increased by 21% (95% CI 8-34%), and those for cardiovascular diagnoses declined by 31% (95% CI 21-39%). Inpatient hospitalizations declined by 10% (95% CI 3-16%). Infants and young children aged 0-4 are well represented in the data, comprising 14.2% of emergency department visits and 21.8% of office and clinic visits.  In this group, emergency department visits overall increased 25% (95% CI 7-47%), while those for respiratory diagnoses increased 70% (95% CI 32-119%). Further, office and clinic visits with respiratory diagnoses increased by 11% (3-19%), despite an overall decrease of 32% (95% CI 29-35%) in office and clinic visits for this group.  

CONCLUSIONS:  Respiratory diagnoses, especially asthma, were elevated during the wildfire event. Patterns in use of care were altered, with fewer people obtaining care at doctor’s offices and clinics. Medi-Cal data was particularly useful for assessing impacts of wildfire among young children.