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Extreme temperatures are known to have negative consequences on the environment and the ecosystem. Already more frequent and intense heat waves are likely to increase in the future due to a projected 0.1–0.2-degree Celsius rise in temperature by 2100. Extreme heat can lead to a spectrum of health-related conditions that range from mild to severe and include, but are not limited to, heat dehydration, cramps, exhaustion syncope and stroke; these are referred to as heat-related illnesses (HRIs).
Extreme temperatures are known to have negative consequences on the environment and the ecosystem . Already more frequent and intense heat waves are likely to increase in the future due to a projected 0.1–0.2-degree Celsius rise in temperature by 2100 . Extreme heat can lead to a spectrum of health-related conditions that range from mild to severe and include, but are not limited to, heat dehydration, cramps, exhaustion syncope and stroke; these are referred to as heat-related illnesses (HRIs) . Without appropriate cooling strategies, extreme heat overextends the body’s capability to regulate its temperature, which can then lead to cardiovascular and/or respiratory compromise, multi-organ failure, impaired coagulation, loss of consciousness, stroke and even death .
The World Health Organization (WHO) estimates that 166,000 deaths have occurred from 1998–2017 due to heat-related illnesses . The 2003 heat wave in Europe increased this number alone with an estimate of 70,000 deaths, while Russia saw 56,000 deaths in the heat wave of 2010 . Other parts of the world have seen similar trends due to heat waves, especially in countries closer to the equator. These countries already experience higher temperatures at baseline, making them more likely to bear the impacts of even small increases in average temperature . Countries in South Asia such as India and Pakistan have experienced heat waves that resulted in thousands of excess deaths .
The WHO and World Meteorological Organization (WMO) collaborated to produce a technical guide as an aid for governments to set up an early warning system for heat waves . While governments in some HICs were able to implement these, other countries, especially those in low resource settings, have not been able to set up systems to mitigate the impacts of extreme heat. In areas where governments do not have resources to drive heat response, communities must make changes to their environment and behaviors to reduce the impact of extreme heat exposure.
Of the 17 articles that were included in the final review, 14 articles were based in HICs, while three were based in LMIC settings. Most (10 out of 17) articles covered community-based interventions in the form of heat action plans and six were from Europe, which had been established by respective local and national governments in response to the 2003 heat wave. The studies ranged from randomized trials ( n = 2), non-randomized or quasi-experimental analyses ( n = 6) to observation or secondary data analyses. Variations in health outcomes reported, the assessment of knowledge, attitude and practices, sample populations, and data sources were observed ( Table 1).
|Author||Location||Study Design||Sample Population||Sample Size||Intervention Type||Primary Outcome||Comparator (If Any)||Quality||Results|
|Mattern 2000||United States||Cross-sectional study||Elderly above 65 years of age||34||Health education, culturally sensitive and age-specific heat-related manual||Risk factors for heat-related mortality||Same population before intervention||Good||67% (pre-test) versus 94% (post-test) knew of a contact for assistance during hot weather|
|Sheridan 2007||United States||Survey||Adults 65 years and above in four North American cities||908||Heat Mitigation Plan||Knowledge||NA||Good||Post-survey, knowledge—90% Behavior modification—46%|
|Fouillet 2008||France||Cohort study||Whole population of France||NA||Awareness; National Heat Wave Action Plan||Excess mortality||Same population before intervention||Good||Expected excess mortality ratio was +27% whereas observed excess mortality ratio was +9%, with an estimated mortality deficit of 2065 deaths|
|Oakman 2010||Australia||Observational study||All individuals above 18 years of age living in the area||328||Media awareness||Knowledge, attitude and practice||NA||Good||54% changed their summer behavior Self-rated understanding of the heat health risks at 7.9 on a 10-point scale, higher than same time last year|
|Morabito 2012||Italy||Cross-sectional study||Elderly above 65 years of age||21,092||Heat Health Warning System (HHWS)||Heat-related mortality||Same population before intervention||Good||Reduction in mortality rate observed only for 75 years and above, only when the maximum temperature time period was considered|
|Schifano 2012||Italy||Pre-post intervention study||Elderly above 65 years of age||50,000 to 2.5 million in the different cities||National heat health prevention program||Heat-related mortality||Same population before intervention||Good||Reduction in elderly mortality from +36.7% to +13.3% with increase in temperature from 9 °C to 12 °C above the 25th percentile|
|Pascal 2012||France||Statistical modeling||NA||~11 million||Heat warning system||Relative risk of mortality||NA||Good||Implementation of heat-action days was associated with a combined loss of relative risk of mortality by −3.3% (95% CI −10.3–4.4)|
|Takahashi 2015||Japan||Randomized controlled trial||Elderly 65 to 84 years of age||1072||Heat health warnings and distribution of water bottles||Knowledge, attitude and practice||No intervention group||Fair||Improvement in the frequency of water intake (p = 0.003) Improvement in frequency of cooling body (p = 0.002) Improvement in the frequency of taking a break (p = 0.088), Reduced activities in the heat (p = 0.093) Increase in hat or parasol use (p = 0.008)|
|de’Donato 2015||Europe||Quasi-Experimental||Deaths that occurred in 9 European cities||1,322,844||Heat Action Plan||Attributable number of deaths||Same population before intervention||Good||In terms of heat attributable mortality, 985, 787 and 623 fewer deaths estimated in Athens, Rome and Paris, respectively. A reduction in mortality risk associated with heat observed only in the three aforementioned cities.|
|Benmarhnia 2016||Canada||Quasi-Experimental||All residents of the island of Montreal||NA||Advisories and emergency public health measures||Heat-related mortality||NA||Good||Daily deaths reduced by an average of 2.52 deaths per day after implementation of the heat action plan|
|Nitschke 2017||Australia||Randomized controlled trial||Elderly above 65 years of age||637||Awareness; Evidence-based information leaflets||Behavior||No intervention group||Good||Intervention group had significant increases in: air conditioner use during hot weather (74.4% versus 63.4%) the use of a wet cloth on face, neck or body to cool down during heat waves (16% vs. 8%) the belief that they had enough information to beat the heat (94% vs. 88%)|
|Hess 2018||India||Time series analysis||People living in Ahmedabad city||Entire population||Awareness and Health Intervention, Heat Action Plan (HAP)||Risk ratio||Pre intervention period, same population||Good||Post-to-pre-HAP non-lagged mortality IRR for maximum temperature over 40C was 0.95 (0.73–1.22) and 0.73 (0.29–1.81) for maximum temperature over 45C. An estimated 2380 deaths post-intervention were avoided|
|Xu 2018||China||Quasi experimental||All individuals above 14 years of age living in the area||2400||Health care networks||Knowledge, attitude and practice||No intervention group||Fair||Intervention groups had 0.387, 0.166 and 0.037 higher knowledge, attitude and practice scores, respectively|
|de’ Donato 2018||Italy||Time series analysis||People residing in 23 Italian cities||NA||Awareness and Health Intervention;Italian National Heat Plan||Attributable number of deaths||NA||Fair||For extreme temperatures. The attributable fraction of heat-related deaths declined from 6.3% in the period 1999–2002 to 4.1% in 2013–2016. More than 1500 heat attributable deaths spared|
|Liotta 2018||Italy||Non-randomized experimental study||Elderly above 75 years of age||12,207||Social Intervention:The Long Live the Elderly (LLE) program to counteract social isolation||Heat-related mortality||No LLE urban areas||Good||Cumulative mortality rates of 25% (Cl 95%: 23–29) and 29% (Cl 95%: 17–43) in LLE versus non LLE urban areas, respectively|
|Martinez-Solanas 2019||Spain||Time series analysis||People living in Spain||NA||Prevention Plan;Spain’s National Heat-Health Prevention Plan (HHPP)||Attributable number of deaths||Same population, pre-intervention||Good||There was a small decrease in mortality attributable to extreme heat (from 0.67% to 0.56%), which was offset by an increase in mortality attributable to moderate heat (from 0.38% to 1.21%). Most significant reduction seen among older individuals.|
|Scortichini 2018||Italy||Time series analysis||Residents in 23 Italian cities||NA||National heat health warning system. Time mortality surveillance systemIdentification of susceptible individuals and treatment||Mortality rateAttributable number of deaths||Same population, pre-intervention||Fair||The effect of extreme temperature reduced after all cities implemented the heat action plan (RR 1.23, 95% 1.15–1.32). Attributable number of deaths reduced from 6.3% to 4.1% (1200 units) during periods of extreme temperature|
The chosen articles elaborate on (1) the establishment of heat action plans and (2) education and awareness campaigns while accommodating age and need-appropriate dissemination of heat-specific preventive actions as effective interventions in reducing the burden of heat-related illnesses.
Heat action plans were implemented mostly in high-income countries across Europe, in Canada and in Japan, and comprised of activities including, but not limited to, establishing a heat monitoring system, also known as the heat health watch warning system, informative campaigns for the general population, the mobilization of health care professionals, volunteers, social workers and trained caregivers in the surveillance and management of individuals with known vulnerabilities, as well as the provision of required infrastructure to cope with extreme temperatures. One study reported the implementation and evaluation of a heat action plan in a low- and middle-income country, India .
Some studies conducted awareness sessions within the community settings that contained guidelines on preventing heat stress, providing information on high-risk population groups (vulnerable groups such as children and the elderly) and provisions for resources to use to prevent heat illness, among other topics, aiming to improve the community’s knowledge, attitudes and perceptions towards the prevention of heat stress. Like heat action plans, these studies were also administered in high- and middle-income countries such as China, the United States and Australia, but the medium used to disseminate the information differed from study to study, as highlighted below, with varying efficacy.
Heat prevention programs were seen to focus on the development and implementation of heat action plans that required multi-sectoral engagement. The studies highlight the fact that local, regional, and national governmental agencies need to take ownership of heat action plans and lead other relevant institutions such as health care facilities, community homes, volunteer and social networks, among others, to manage multiple components of a multi-pronged heat action plan.
Another important aspect in the prevention of HRIs and successful heat prevention plans is the regular surveillance of variable temperatures throughout the year. Prior knowledge of impending extreme temperatures can facilitate the initiation of prevention strategies as well as early installment of programs such as relief camps. We encourage more collaboration of governments with the World Meteorological Organization to determine appropriate heat health warning systems to better classify and forecast heat emergencies on a more consistent and reliable basis .
While this entry provides a menu of sorts on the packages of interventions that can be created to have a mitigating effect on the impact of extreme heat on human health, the lack of evidence around the effectiveness of these interventions in low-resource settings cannot be undermined. It is worthwhile to investigate the real-time impact of such interventions in low-resource settings as well as conduct studies to tease out the most beneficial package of interventions that are most effective, both in health outcomes and cost structures.