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Three Part Question

What are the impacts of [extreme heat] on [climate sensitive emergency health conditions] and [emergency departments]?

Clinical Scenario

Climate change is the biggest global health threat of the 21st century. According to the recent Intergovernmental Panel on Climate Change, the global mean temperature is projected to rise by 1.4 to 5.8 degrees by the end of the century. Extreme temperatures overwhelm the body's heat regulatory mechanism, and multi-system organ dysfunction results.

In light of recent global heatwaves, it is imperative that emergency care clinicians appreciate the diversity of climate sensitive emergency health conditions and their impacts on emergency care systems.

Search Strategy

Literature search was conducted from Medline, Embase, Global Health and grey literature databases. Articles were limited to English language published between 1990 and August 2020.
[exp Emergency Medicine/ OR exp Emergency Medical Services/ OR exp Emergency Service, Hospital/ OR exp Resuscitation/ OR exp Disaster Medicine/ OR exp Emergency Treatment/ OR exp Emergencies/ OR (emergency adj2 (system* or care or service*)).mp. OR (emergency adj1 (medicine or care or room or department* or unit* or service* or practice or treatment*)).mp.] AND

[exp Climate Change/ OR exp Greenhouse Effect/ OR exp Greenhouse Gases/ OR exp Global Warming/ OR (global adj1 (warming or heating)).mp. OR Greenhouse Gases/ OR ((weather or environment) adj1 change*).mp.] AND

[exp Cardiovascular Diseases/ OR exp Respiratory Tract Diseases/ OR exp Respiratory Tract Infections/ OR exp Asthma/ OR exp Pulmonary Disease, Chronic Obstructive/ OR exp Cerebrovascular Disorders/ OR
exp Kidney Diseases/ OR exp Heat Stroke/ OR exp Communicable Diseases/ OR exp Bacterial Infections/ OR exp Virus Diseases/ OR exp Parasitic Diseases/ OR exp Mycoses/ OR exp Zoonoses/ OR exp Pandemics/ OR exp Diarrhea/ OR exp Mental Health/ OR exp "Wounds and Injuries"/ OR exp Death ]

Limit to English

Search Outcome

The search yielded a total of 192 articles after the removal of duplicates. 21 articles addressed heatwaves and their impacts on emergency health and emergency care systems.
These were all peer reviewed original research articles.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Basu R et al 2012 California, USA	All age patients visiting EDs in California state between 1 May to 30 September 2005-8. Over 1.2 million ED visits were included.	Time-stratified case crossover	Association between mean daily temperatures and cause-specific ED visits (ICD-9)	Increased ED visits for following conditions: hypotension 12.7 (95% CI 8.3 to 17.4), diabetes 4.3 (95% CI 2.8 to 5.9), intestinal infection 6.1 (95% CI 3.3 to 9.0), dehydration 25.6 (95% CI 21.9 to 29.4), Acute Renal Failure 15.9 (95% CI 12.7 to 19.3), and heat illness 393.3 (95% CI 331.2 to 464.5).	Quality of ED records determined overall study data, limiting some subgroup analysis for individual vulnerable groups
Hess JJ et al 2014 USA	All age ED visits 2006-2010 from May -September 2006-2010 with any acute heat illness (ICD-9) using a nationally representative sample derived from the Nationwide Emergency Department Sample (NEDS)	Retrospective data analysis	Population-based rates for acute heat illness ED visits.	326,497 heat illness ED visits were recorded in the sample during 2006-2010.	Exposures of other natural and man-made aetiology accounting for outcomes cannot be excluded. No information is given regarding inter-rater reliability of ED diagnoses
			Demographic and comorbid conditions associated with ED visits or death in EDs with acute heat illness	Adjusted odds of ED visits and deaths in EDs were higher among males OR 1.64 (95% CI 1.59 to 1.7), urban OR 1.36 (95% CI 1.29, 1.44), and many chronic conditions; hematological OR 9.05 (95% CI 8.45 to 9.69), genitourinary OR 3.48 (95% CI 3.25 to 3.72) , nervous OR 3.22 (95% CI 3.05 to 3.39), endocrine OR 2.85 (95% CI 2.76 to 2.95), mental OR 2.75 (95% CI 2.66 to 2.84), cancer OR 2.66 (95% CI 2.3 to 3.07), circulatory OR 2.44 (95% CI 2.36 to 2.53) and respiratory OR 1.92 (95% CI 1.83 to 2.02).
Knowlton K et al 2009 California, USA	All age ED visits across the California state during the 2006 heatwave (15 July- 1 Aug 2006) with all cause and cause-specific illnesses (ICD-9)	Cross-sectional study	ED visits during the 2006 heatwave vs the reference period rates (8-14 July and 12-22 Aug 2006)	All-cause ED visits increased (RR 1.03 95% CI 1.02-1.04) corresponding to 16,166 additional ED visits across the state. More than 6-fold increase in heat related ED visits was reported across the state (RR 6.3 95% CI 5.67-7.0). Increases in ED visits were also seen with cardiovascular diseases RR 1.02 (95% CI 1.01–1.03), diabetes RR 1.03 (95% CI 1.01–1.04), and nephritis RR 1.06 (95% CI 1.04–1.09). ED visits increased across all age categories (< 5, 5-64, > 64), but the greatest increase was observed among young chlldren (< 5) RR 1.05 (95% CI 1.04-1.07). Significant increases in ED visits were reported for most of the race groups but the greatest increase was seen for the Latino/ Hispanic group RR 1.04 (95%CI 1.03-1.05)	Potential effect modification by other factors e.g. air pollution was not addressed.
Wang U et al 2020 China	All age ED visits in 18 provinces with different climatic characteristics in China from June-August 2014-2017 for all-cause and cause-specific illnesses (ICD-10)	Time-stratified case crossover	Association between mean daily temperatures and ED visits	1 °C increase in daily mean temperature was associated with 1.07% (95% CI, 0.46– 1.67) increase in ED visits across all study regions. Attributable fraction due to high temperatures was 8.64% (95% CI -1.16 - 17.16) for overall ED visits, 11.7% (95%CI 1.90–20.30%) for people living in southern China, 10.80% (95%CI, 2.10–18.50%) for people living in subtropical monsoon zone and 12.65% (95%CI, 1.77–22.11%) for county population. 1°C increase in temperature resulted in 2.68% (95% CI, 0.45– 4.96) increased ED visits with endocrine disease, 2.52% (95% CI, 1.35–3.70%) increase with respiratory disease, 1.54% (95% CI, 0.67–2.43%) increase in digestive disease, and 1.35% (95% CI, 0.39–2.32%) increase in injury. People under 18 were most vulnerable to high temperatures 1.91% (95% CI 0.69-3.15)	ED visits for children are likely to be an underestimate as many children bypass EDs and attend specialised children's hospitals directly. Data from fixed meteorological and air monitoring stations were used, introducing potential errors in exposure measurement
Watson KE et al 2020 Australia	All age all-cause ED admissions in Tasmania between Jan 2003 to Dec 2010.	Retrospective data analysis	Association between ED admissions and mean ambient temperatures	Relative risk of ED admissions between 2003–2010 was significantly higher for temperatures above 27°C RR 1.18 (95% CI: 1.07–1.31)	ED admission data rather than attendance data were analysed. This is likely to be a significant underestimate of the extreme heat burden on emergency department. Types of admissions and vulnerable groups were not analysed
				A lag effect exists, increasing the likelihood of ED admissions for further 14 days.
Schaffer A et al 2012 Australia	All age ED visits and EMS calls during 2011 heatwave between 30 January to 6 February in New South Wales, Australia	Interrupted time series	Excess all-cause ED visits, EMS call outs and all-cause mortality during 2011 heatwave compared to referent periods	All cause ED visits increased by 2% (95% CI 1.01-1.03), all cause EMS calls increased by 14% (95% CI 1.11-1.16), and all-cause mortality increased by 13% (95% CI 1.06-1.22). Elders > 75 years had the highest excess rates of all outcomes, 8% excess ED visits (95% CI 1.04-1.11), 17% excess EMS calls (95% CI 1.12-1.23), and 12% excess deaths (95% CI 1.03-1.23).	Potential effect modification by other factors such as air pollution was not addressed
Wang YC et al 2014 Taiwan	All age patients attending EDs between 2000 and 2009 in Taipei	Interrupted time series	Association between cause-specific (ICD-9) ED visits and ambient temperature	At 32 ºC, cumulative 4-day relative risk (RR) for ED visits increased for Chronic Renal Failure (RR = 2.36; 95% CI 1.33-4.19), Diabetes Mellitus (RR = 1.69; 95% CI: 1.09-2.61) and accidents (RR = 1.23; 95% CI 1.14-1.33)	Incomplete ED data recording limited subgroup analysis of individual vulnerable groups
Cheng J et al 2019 Australia/ China	54 studies from 20 countries	Systematic review and Meta-analysis	Heatwave effects on cardiovascular and respiratory mortality and morbidity. Categories of morbidity included hospital admissions, ED visits, and EMS callouts.	Significant associations reported between heatwaves and cardiovascular mortality (risk estimates (RE): 1.149, 95% CI 1.090- 1.210) and respiratory mortality (RE: 1.183, 95%CI 1.092-1.282). For disease specific causes, positive associations reported for IHD (RE:1.23, 95%CI: 1.07-1.42), stroke (RE:1.19, 95%CI: 1.04-1.36), and heart failure (RE: 1.10, 95%CI: 1.04-1.18) mortality. Heatwaves not statistically associated with cardiovascular and respiratory morbidities (RE: 0.999, 95%CI: 0.996-1.002 for cardiovascular morbidity; RE: 1.043, 95%CI: 0.995-1.093 for respiratory morbidity)	High heterogeneity among studies limit a clearer picture of how extreme heat affects cardiovascular and respiratory morbidities in different settings.
Lavigne E et al 2014 Canada	All age ED visits in Toronto between April 2002 to March 2010 with cardiovascular or respiratory diseases (ICD-10)	Interrupted time series	Effects of extreme heat and cold on cardio-respiratory ED visits among persons with comorbiditites vs persons with no comorbidities	There was an increased risk of cardiovascular ED visits among persons with comorbid diabetes (Relative effect modification (REM) = 1.12; 95% CI: 1.01 – 1.27) when exposed to cumulative short-term effect of extreme heat. Associations were also found for persons with comorbid respiratory disease (REM= 1.17; 95% CI: 1.02 – 1.44)) and cancer (REM= 1.20; 95% CI: 1.02 –1.49) on respiratory ED visits compared with persons without these comorbid conditions	Data were obtained from fixed site monitoring stations for ambient temperatures rather than measuring individual exposures, possibly leading to measurement errors
Mullins and White 2019 USA	All age ED visits with mental health related issues in California 2005-2016	Interrupted time series	Impacts of ambient temperatures on mental health related ED visits and suicide rates	One day < 40 F and one day > 80 F led to 0.43 fewer and 0.33 more mental health related ED visits per 100,000 residents, respectively. One day <30F and one day >80F led to 0.0044 fewer and 0.0025 more suicides per 100,000 residents, respectively.	Other potential effect modifiers were not considered in the analysis
Toloo GS et al 2015 Australia	All age heat-related presentations (ICD 10) to 11 EDs in Queensland, Australia during summer seasons 2000-2012	Interrupted time series	Impacts of heatwaves on ED visits	All-cause ED visits increased significantly (RR) = 4.9, 95% CI: 3.8,-6.3 and (RR) = 18.5, 95% CI 12.0- 28.4, when two or more successive days with daily max temperature > 34 C (HWD1) and >37 C (HWD2) , respectively	Some incomplete data precluded subgroup analyses addressing vulnerable groups.
				Heat-related visits increased significantly among older group (>75 years) RR = 9.17, 95% CI: 5.45- 15.44 (HDW1) and RR 37.55, 95% CI: 18.34-76.86 (HWD2)
				Average length of stay in ED significantly increased by >1 hour (HWD1) and >2 hours (HWD2).
Imai N et al 2018 Japan	Adults > 18 years attending ED between Jan 2015 to Dec 2016	Retrospective study of ED case notes	Impact of age on the seasonal prevalence of hyponatremia	Prevalence of hyponatremia was significantly higher in the elderly group (>65 years) than in the adult group (17.0% vs. 5.7%, p < 0.001) in all seasons. Significant correlation reported between high ambient temperature and prevalence of hyponatremia (r = 0.510, p = 0.011).	Retrospective and single centred study
Xu Z et al 2019 Australia	All age ED visits across Queensland, Australia January 2013 to December 2015	Interrupted time series	Heatwave impacts on cause-specific ED visits (ICD-10 coding) in urban and rural communities of Queensland	ED visits increased for endocrine, nutritional and metabolic diseases (RR: 1.18, 95% CI: 1.04–1.34), diseases of the nervous system (RR: 1.09, 95% CI: 1.02–1.17), and diseases of the genitourinary system (RR: 1.05, 95% CI: 1.00–1.09) during heatwave days. The effect of heatwaves on total ED visits was similar for rural (RR: 1.04, 95% CI: 1.01–1.07) and urban regions (RR: 1.04, 95% CI: 1.00–1.07)	Air pollutants were only controlled in some communities. Relatively short study period limits analysis of temporal change in people's vulnerability to heatwaves
Vicedo-Cabrera AM et al 2020 USA	All age ED visits with kidney stone presentations to 68 EDs in South Carolina between January 1997 and September 2015	Time-stratified case crossover design	Sex/ other characteristics influencing temperature dependent kidney stone presentations	Daily wet-bulb temperatures at the 99th percentile were associated with a greater increased relative risk (RR) of kidney stone presentations over 10 days for males (RR 1.73; 95% CI: 1.56- 1.91) than for females (RR 1.15; 95% CI: 1.01- 1.32; P<0.001)	Failure to consider effect modification by other influencing factors such as fluid intake, air conditioning, etc
Cervellin G et al 2012 Italy	All age patients presenting to University Hospital Parma ED, Italy between January 2002 to December 2010 with confirmed renal colic	Retrospective study of ED data	Impacts of extreme heat on ED visits with renal colic	Renal colic peaked in July (4.1 cases of renal colic per day) and reached nadir during the winter (2.7 cases of renal colic per day in February). There was a significant correlation between the mean number of renal colic cases per day and both mean daily temperature (positive association, R = 0.93; p < 0.0001) and mean daily humidity (negative association, R = -0.82; p < 0.0001).	Retrospective and single centred study
McTavish RK et al 2018 Canada	Older adults (mean age, 80 years) in Ontario with acute kidney injury (inpatient admissions or ED visits) from April through September 2005 to 2012	Matched case control study	Impact of extreme heat on acute kidney injury	Heat periods were significantly associated with higher risk for AKI (adjusted OR, 1.11; 95% CI, 1.00-1.23).	Potential effect modification by other factors such as fluid intake and protection from heat were not considered.
Sherbakov T et al 2018 USA	All age cause-specific (ICD-9 coding) ED admissions across California from May - October 1999–2009	Interrupted time series	Association between heatwaves and hospitalizations across 16 climate zones of California	Positive associations with heatwaves reported for Acute Renal Failure RR 1.21 (95% CI 1.15–1.28), appendicitis RR 1.11 (95% CI 1.08–1.15), dehydration RR 1.20 (95% CI 1.16–1.24), Ischaemic stroke RR 1.03 (95% CI 1.01–1.05), mental health RR 1.04 (95% CI 1.01–1.07), non-infectious enteritis RR 1.05 (95% CI 1.02–1.08), and primary diabetes mellitus RR 1.06 (95% CI 1.03–1.09)	Incomplete hospital records limited individual vulnerable group analysis.
van Loenhout JAF et al 2018 The Netherlands	All age patients visiting EDs of all Dutch hospitals with heat-related illness, respiratory and circulatory disease and fractures of femur (ICD-9) between May- September 2002- 2007	Interrupted time series	Association between extreme heat and ED visits in the Netherlands	Positive association between increasing temperatures above 26 °C and relative risk for ED visits for heat related illness and Respiratory disease across all age groups. This relationship is strongest in the 85+ group, heat-related illness (RR 1.16 95% CI 1.10- 1.22), and Respiratory disease (RR 1.11 95% CI 1.07- 1.15), respectively.	Other potential effect modifiers were not considered in the analysis
Newitt S et al 2016 UK	All age patients in England bitten by arthropods 2000-2013, captured by sentinel surveillance systems	Retrospective ecological study	Association between ambient temperature and arthropod bites	Arthropod bites were positively associated with temperature. Incidence rate ratios (IRRs) increased 1.24 (95% CI 1.23–1.25) for ED visits across England	The true incidence of arthropod bites is likely to be much higher as only those with the most severe reaction is likely to have sought healthcare services Broad diagnostic coding means that the study is unable to differentiate between different species of arthropods.
Kingsley SL et al 2016 USA	All age ED visits during 2005- 2012 in Rhode Island, USA	Interrupted time series	Association between extreme heat and all cause and heat-related ED visits	Increase maximum daily temperature from 75 to 85 F associated with 1.3% (95% CI 0.4- 2.2) and 23.9 % (95% CI 18.9- 29.2) higher rates of all-cause and heat-specific ED visits, respectively	The study did not explore other potential determinants of temporal variation in rates of ED admissions
van der Linden N et al 2019 Australia, Botswana, Netherlands, Pakistan, USA	All age patients attending EDs in 18 hospitals in five countries for variable duration between 2009-2016.	Interrupted time series	Association between heatwaves and ED visits	During heatwaves, biggest increase in ED visits were children ages 5–11 years in California, elders 65–74 years in Karachi, and 75–84 years in the Netherlands	The study did not consider delayed effects or influences of other environmental factors

Comment(s)

There is no standardised definition of a heatwave. The accepted definition refers to the elevation of an ambient temperature above an average threshold sustained for a defined period of time. This threshold varies geographically. The heterogeneous nature of existing data, combined with the inherent diversity of climate-specific epidemiological and socio-economic variables of each locality present a significant logistic challenge in conducting systematic reviews on this topic. Extreme heat is one of the many climate change driven effects, along with increased air pollutants, climatic disasters and altered infectious disease epidemiology, inter alia. This review focused on the impacts of extreme heat on emergency departments. Both increased all-cause and heat-related (heat exhaustion, heat stroke, dehydration, acute renal failure, electrolyte imbalances) ED visits are reported with increased ambient temperatures around the world. The highest relative increase is observed among the elderly (> 65 years), the young (< 5 years), males, and those with non-communicable disease. Increased ED visits are also reported for the following conditions; cardiovascular disease, diabetes, renal colic, appendicitis, gastrointestinal infectious disease, arthropod bites, chronic renal failure, respiratory disease, injury, and mental health disorders. The elderly are disproportionately vulnerable to the effects of extreme heat due to their sensory, cognitive and physical disabilities, compounded by limited social support and financial means. The bigger surface to body ratio of young children increases their vulnerability to heat stress and dehydration. The magnitude of heatwave influence on ED visits varies across studies, and is dependent on the geographical, demographic, and socioeconomic characteristics of the community. Most studies did not control for individual and community adaptation behaviors, for example the installation of air conditioning, fluid intake, existing community health system infrastructure and support networks, etc. Absence of measures to control for effect modifiers precludes meaningful comparison of outcomes between areas with different geographical, demographic and health infrastructure variables. Public health response could support targeted interventions at a local level, for example public education to vulnerable groups to avoid exposure to risk factors, and avoidance of prescribing high-risk medications (e.g. diuretics, antipsychotics, anticholinergics) which interfere with the body’s thermoregulation and increase vulnerability to extreme heat among the elderly. Finally, most included studies were conducted in high income countries which have the resources to build climate resilient emergency care pathways. Further research is urgently needed to develop empirical examples that inform adaptation measures across a range of low- and middle-income countries where the impact of climate change is likely to be most profound.

Clinical Bottom Line

The review demonstrates that heatwaves are placing increasing demands on the emergency care systems. Extreme heat results in excess ED visits in many countries with multi-organ impacts resulting in excess morbidity.

References

1. Basu R et al The effect of high ambient temperature on emergency room visits Epidemiology 2012; 23(6): 813-20
2. Hess JJ et al Summertime acute heat illness in U.S. emergency departments from 2006 through 2010: analysis of a nationally representative sample Environ Health Perspect 122(11): 1209-15
3. Knowlton K et al The 2006 California heat wave: impacts on hospitalizations and emergency department visits Environ Health Perspect 2009; 117(1): 61-7
4. Wang Y et al High temperatures and emergency department visits in 18 sites with different climatic characteristics in China: Risk assessment and attributable fraction identification Environ Int 2020; 136: 105486
5. Watson KE et al The impact of extreme heat events on hospital admissions to the Royal Hobart Hospital J Public Health (Oxf 2020; 42(2): 333-339
6. Schaffer A et al Emergency department visits, ambulance calls, and mortality associated with an exceptional heat wave in Sydney, Australia, 2011: a time-series analysis. Environ Health 2012; 11(1):3
7. Wang YC et al Association between temperature and emergency room visits for cardiorespiratory diseases, metabolic syndrome-related diseases, and accidents in metropolitan Taipei PLoS ONE 2014; 9(6): e99599.
8. Cheng J et al Cardiorespiratory effects of heatwaves: A systematic review and meta-analysis of global epidemiological evidence Environ Res 2019; 177:108610
9. Lavigne E et al Extreme ambient temperatures and cardiorespiratory emergency room visits: assessing risk by comorbid health conditions in a time series study Environ Health 2014; 13(1): 5
10. Mullins and Whitenjkkm Temperature and mental health: Evidence from the spectrum of mental health outcomes J Health Econ 2019; ; 68: 102240
11. Toloo GS et al The impact of heatwaves on emergency department visits in Brisbane, Australia: a time series study Crit Care 2014; 18: R69
12. Imai N et al Seasonal prevalence of hyponatremia in the emergency department: impact of age BMC Emerg Med 2018; 18(1): 41
13. Xu Z et al Assessing heatwave impacts on cause-specific emergency department visits in urban and rural communities of Queensland, Australia Environ Res 2019 ;168: 414-419
14. Vicedo-Cabrera AM et al Sex differences in the temperature dependence of kidney stone presentations: a population-based aggregated case-crossover study Urolithiasis 2020; 48(1): 37-46
15. Cervellin G et al Mean temperature and humidity variations, along with patient age, predict the number of visits for renal colic in a large urban Emergency Department: results of a 9-year survey J Epidemiol Glob Health 2012; 2(1): 31-8
16. McTavish RK et al Association Between High Environmental Heat and Risk of Acute Kidney Injury Among Older Adults in a Northern Climate: A Matched Case-Control Study Am J Kidney Dis 2018; 71(2): 200-208
17. Sherbakov T et al Ambient temperature and added heat wave effects on hospitalizations in California from 1999 to 2009 Environ Res 2018; 160: 83-90
18. van Loenhout JAF et al Heat and emergency room admissions in the Netherlands BMC Public Health 2018; 18(1):108
19. Newitt S et al The use of syndromic surveillance to monitor the incidence of arthropod bites requiring healthcare in England, 2000–2013: a retrospective ecological study Epidemiol Infect 2016; 144(11): 2251-9
20. Kingsley SL et al Current and Projected Heat-Related Morbidity and Mortality in Rhode Island Environ Health Perspect 2016; 124(4): 460-7
21. van der Linden N et al The use of an 'acclimatization' heatwave measure to compare temperature-related demand for emergency services in Australia, Botswana, Netherlands, Pakistan, and USA PLoS One 2019 28;14(3)