Effect of weather on medical patient volume at Kansas Speedway mass gatherings.

INTRODUCTION Provision for the safety and health care of persons attending mass-gathering events presents unique challenges to organizers. This study was designed to determine the factors that contribute to patients seeking medical care during these events. METHODS We performed a retrospective review of patient care records for visits that occurred during race weekends at the Kansas Speedway from April 2007 to October 2010. Data were collected regarding the overall gathering size of each event to calculate the number of patient encounters per 10,000 attendees. Patients' final disposition was determined to calculate the transfer-to-hospital rate per 10,000 attendees. Weather data, including temperature, humidity, and precipitation, were documented for each event. Negative binomial regression was used to test the relationship between weather factors and the rate of patient encounters. RESULTS Twenty-two event days over 6 race weekends were evaluated, with a total of 1305 patients (58% male; mean age: 37 years), a mean patient encounter rate of 13 per 10,000 attendees, and a mean transfer-to-hospital rate of 0.24 per 10,000 attendees. Our regression model demonstrated that each 0.55°C (1°F) increase in daily mean temperature was associated with a 4% increase in the rate of total complaints (P = .03) and a 6% increase in major trauma presentations (P = .019). Major trauma events were 2.4 times more frequent at ambient temperatures >17.2°C (63°F) (P = .03). Each inch of precipitation was associated with a 61% decrease in total patient volume (P = .05). CONCLUSION Weather factors significantly and predictably affect the use of medical services at the Kansas Speedway. Such data regarding mass-gathering events can be used for resource planning.