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Research Christmas 2017: Natural Phenomena

Stormy weather: a retrospective analysis of demand for emergency medical services during epidemic thunderstorm asthma

BMJ 2017; 359 doi: (Published 13 December 2017) Cite this as: BMJ 2017;359:j5636
  1. Emily Andrew, research governance manager12,
  2. Ziad Nehme, senior research fellow123,
  3. Stephen Bernard, medical director124,
  4. Michael J Abramson, deputy head2,
  5. Ed Newbigin, associate professor5,
  6. Ben Piper, chief operating officer6,
  7. Justin Dunlop, manager7,
  8. Paul Holman, director7,
  9. Karen Smith, director123
  1. 1Centre for Research and Evaluation, Ambulance Victoria, Doncaster, VIC 3108, Australia 3108
  2. 2Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC 3004, Australia
  3. 3Department of Community Emergency Health and Paramedic Practice, Frankston, VIC 3199, Australia
  4. 4Intensive Care Unit, The Alfred Hospital, Melbourne, VIC 3004, Australia
  5. 5School of BioSciences, University of Melbourne, Melbourne, VIC 3052, Australia
  6. 6Emergency Services Telecommunications Authority, Burwood East, VIC 3151, Australia 3151
  7. 7Emergency Management Unit, Ambulance Victoria, Melbourne, VIC 3000, Australia
  1. Correspondence to: Emily Andrew emily.andrew{at}
  • Accepted 27 November 2017


Objectives To describe the demand for emergency medical assistance during the largest outbreak of thunderstorm asthma reported globally, which occurred on 21 November 2016.

Design A time series analysis was conducted of emergency medical service caseload between 1 January 2015 and 31 December 2016. Demand during the thunderstorm asthma event was compared to historical trends for the overall population and across specific subgroups.

Setting Victoria, Australia.

Main outcome measures Number of overall cases attended by emergency medical services, and within patient subgroups.

Results On 21 November 2016, the emergency medical service received calls for 2954 cases, which was 1014 more cases than the average over the historical period. Between 6 pm and midnight, calls for 1326 cases were received, which was 2.5 times higher than expected. A total of 332 patients were assessed by paramedics as having acute respiratory distress on 21 November, compared with a daily average of 52 during the historical period. After adjustment for temporal trends, thunderstorm asthma was associated with a 42% (95% confidence interval 40% to 44%) increase in overall caseload for the emergency medical service and a 432% increase in emergency medical attendances for acute respiratory distress symptoms. Emergency transports to hospital increased by 17% (16% to 19%) and time critical referrals from general practitioners increased by 47% (21% to 80%). Large increases in demand were seen among patients with a history of asthma and bronchodilator use. The incidence of out-of-hospital cardiac arrest increased by 82% (67% to 99%) and pre-hospital deaths by 41% (29% to 55%).

Conclusions An unprecedented outbreak of thunderstorm asthma was associated with substantial increase in demand for emergency medical services and pre-hospital cardiac arrest. The health impact of future events may be minimised through use of preventive measures by patients and predictive early warning systems.


  • Contributors: EA, KS, and MJA conceived the study. EA conducted the initial literature search and drafted the manuscript. EA, EN, and BP collected the data. EA and ZN performed the statistical analyses; EA, ZN, KS, SB, MJA, EN, and BP contributed to data interpretation. All other authors reviewed the manuscript and made critical revisions for intellectual property.

  • Funding: None.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at and declare: MJA holds investigator initiated grants from Pfizer and Boehringer-Ingelheim for unrelated research; other authors had no support from any organisation for the submitted work; all authors had no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could have influenced the submitted work.

  • Ethical approval: This study was approved by Monash University Human Research Ethics Committee (#7739).

  • Data sharing: Case and patient level datasets are available from the corresponding author on request.

  • Transparency: All authors take responsibility for the integrity of the data and the accuracy of the data analysis. The manuscript is an honest, accurate and transparent account of the study; no aspects of the study have been omitted.

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