The Effect of Heat Waves on Ambulance Attendances in Brisbane, Australia

Introduction: Heat waves have significant impacts on mortality and morbidity. However, little is known regarding effects on pre-admission health outcomes such as ambulance attendances, particularly in subtropical regions. Problem: This study investigated both main temperature effects and the added effects of heat waves on ambulance attendances in Brisbane, a subtropical city in Australia. Methods: Daily data relating to 783,935 ambulance attendances, along with data on meteorological variables and air pollutants, were collected for the period 2000-2007. Ambient temperature (main) effects were assessed using a distributed lag nonlinear approach that accounted for delayed effects of temperature, while added heat wave effects were incorporated separately using a local heat wave definition. Effect estimates were obtained for total, cardiovascular and respiratory attendances, and different age groups. Results: Main effects of temperature were found for total attendances, which increased by 50.6% (95% CI, 32.3%-71.4%) for a 9.5 degrees C increase above a reference temperature of 29 degrees C. An added heat wave effect on total attendances was observed (18.8%; 95% CI, 6.5%-32.5%). Significant effects were found for both respiratory and cardiovascular attendances, particularly for those aged 65 and above. Conclusion: Ambulance attendances can be significantly impacted by sustained periods of high temperatures, and are a valid source of early detection of the effects of extreme temperatures on the population. The planning of ambulance services may need to be adapted as a consequence of increasing numbers of heat waves in the future. Ambulance attendance data also should be utilized in the development of heat warning systems and climate change adaptation strategies.