Hourly associations between heat and ambulance calls.
BACKGROUND
The response speed of ambulance calls is very crucial to rescue patients suffering immediately life threatening conditions. The serious health outcomes might be caused by exposing to extreme heat only several hours before. However, limited evidence is available on this topic. This study aims to examine the hourly association between heat and ambulance calls, to improve the ambulance services and to better protect health.


METHODS
Hourly data on ambulance calls for non-accidental causes, temperature and air pollutants (PM10, NO2, and O3) were collected from Brisbane, Australia, during 2001 and 2007. A time-stratified case-crossover design was used to examine the associations between hourly ambulance calls and temperature during warm season (Nov, Dec, Jan, Feb, and Mar), while adjusting for potential confounders. Stratified analyses were performed for sex and age groups.


RESULTS
Ambulance calls peaked at 10am for all groups, except those aged <15 years at 19pm, while temperature was hottest at 13pm. The hourly heat-ambulance calls relationships were non-linear for all groups, with thresholds between 27 °C and 31 °C. The associations appeared immediately, and lasted for about 24 h. There were no significant modification effect by sex and age.


CONCLUSIONS
The findings suggest that hot hourly temperatures (>27 °C) increase the demands of ambulance. This information is helpful to increase the efficiency of ambulance service then save lives, for example, preparing more ambulance before appearance of extremely hot temperature in combination with weather forecast. Also, people should better arrange their time for outdoor activities to avoid exposing to extreme hot temperatures.
Division of Epidemiology and Biostatistics, School of Public Health, University of Queensland, Brisbane, Australia. Electronic address: y.guo1@uq.edu.au.
Yuming
Y
Guo
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000393:Air Pollutants / Q000032:analysis*; D000552:Ambulances; D018592:Cross-Over Studies; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D017711:Nonlinear Dynamics; D011793:Queensland; D012621:Seasons; D012737:Sex Factors; D013696:Temperature; D014887:Weather
D000393:Air Pollutants
Ambulance calls; Case-crossover design; Hourly heat effect