Elsevier

The Lancet

Volume 375, Issue 9717, 6–12 March 2010, Pages 856-863
The Lancet

Review
Health effects of hot weather: from awareness of risk factors to effective health protection

https://doi.org/10.1016/S0140-6736(09)61711-6Get rights and content

Summary

Because of the increasing concerns about climate change and deadly heatwaves in the past, the health effects of hot weather are fast becoming a global public health challenge for the 21st century. Some cities across the world have introduced public health protection measures, with the timely provision of appropriate home-based prevention advice to the general public being the most crucial point of intervention. In this Review, we report current epidemiological and physiological evidence about the range of health effects associated with hot weather, and draw attention to the interplay between climate factors, human susceptibility, and adaptation measures that contribute to heat burdens. We focus on the evidence base for the most commonly provided heat-protection advice, and make recommendations about the optimum clinical and public health practice that are expected to reduce health problems associated with current and future hot weather.

Introduction

One of the most direct health effects arising from climate change is expected to be increased rates of mortality and morbidity associated with exposure to high ambient temperatures.1 Many countries already have a burden of heat-related mortality that manifests during heatwaves but is insidious throughout the summer.2 Additionally, with future susceptibility likely to be increased with ageing populations in high-income countries and rapid urbanisation in many low-income countries, the health effects of hot weather are fast becoming a global public health challenge for the 21st century.3, 4

In recognition of this likely increase, cities in North America and Europe, and parts of Asia and Australia, have introduced public health protection measures. Prominent among these are heat health warning systems that trigger community alerts and emergency actions in response to forecasts of adverse weather conditions.5 Because heat-related illness is largely avoidable, the most crucial point of intervention concerns the use of appropriate prevention strategies by susceptible individuals and their carers.6 Although such home-based prevention advice already forms an integral part of many heat health warning systems, the extent to which the advice is based on medical evidence is unclear. Knowledge of effective prevention and first-aid treatment, besides an awareness of potential side-effects of prescription drugs during hot weather, is crucial for physicians and pharmacists.

We review the reported effects of ambient heat exposure on individuals and communities, and add to evidence from previous epidemiological3 and public health reviews7, 8, 9 to draw attention to the latest knowledge about heat-related health. Additionally, we provide information about the most commonly offered advice to the public about heat protection, and the evidence base for such guidance.

Section snippets

Physiological effects of heat

Whereas human adaptation to cold environments is greatly assisted by behavioural responses (eg, wearing additional layers of clothing), adaptation to heat is dependent on the body's ability to act as a natural cooling system. Human beings maintain an internal temperature within a narrow range around 37°C, independently of ambient temperature fluctuations.10 Heat homoeostasis is achieved through thermoregulatory functions, controlling the gain or loss of heat. The processes are conduction

Online heat-related health advice

The table shows the websites of 44 health-related or weather-related organisations retrieved in our internet search for public guidance about heat protection. The most commonly offered advice is shown in panel 1. Aspects of protection emphasised on the websites did not always indicate clearly which issues were of greatest concern, and recommendations were rarely supported by reference citations. The amount and quality of information provided was not necessarily greater in jurisdictions that had

Evidence base for commonly offered advice

Alcohol has a diuretic effect that varies according to the alcohol content of drinks. Although increases in urinary output of 10 mL/g of alcohol consumed69 might not be a cause for concern with drinks that have a large fluid-to-alcohol content (such as beer), the bioavailability of fluid content can be attenuated by nearly 50% with drinks containing a high proportion of alcohol (eg, whisky). In addition to impairment of judgment, consumption of large amounts of alcohol diminishes heart

Evidence and recommendations

Effects of heat on morbidity are generally smaller in magnitude and less consistent than those on mortality, supporting evidence that the effects of heat happen quickly and often before people come to medical attention.25 Although in most plans for protection against hot weather, this situation is taken into consideration by use of outreach strategies to protect people within the community, the advice given to the general public might not always be based on clear evidence.

Drug use is often

Conclusion

With rises in temperatures expected in the coming decades, use of evidence-based health protection during hot weather by the general public and public health practitioners will have a key role in determining future heat burdens.

Search strategy and selection criteria

The search strategy consisted of:

  • 1

    A literature search to provide an overview of the health effects of hot weather and risk factors.

  • 2

    An internet search to establish what heat-protection advice is provided by public health authorities and other agencies.

  • 3

    A literature search to review the evidence base of the guidance identified in (2).

For (1) and (3), we searched PubMed, Embase, Geobase, and Desastres for reports in English or French using the combinations of MeSH terms “weather”

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