High temperatures
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The Impact of High Temperatures on Health and Environment
High Temperatures and Pregnancy Outcomes
Preterm Birth, Low Birth Weight, and Stillbirths
Exposure to high temperatures during pregnancy has been linked to adverse birth outcomes. A systematic review and meta-analysis found that preterm births were more common at higher temperatures in 40 out of 47 studies. Specifically, the odds of preterm birth increased by 1.05-fold per 1°C rise in temperature and 1.16-fold during heatwaves. Additionally, higher temperatures were associated with reduced birth weight in 18 out of 28 studies and increased stillbirths in all eight studies reviewed, with stillbirths rising by 1.05-fold per 1°C increase in temperature. These effects were more pronounced among women in lower socioeconomic groups and at age extremes1.
Global Trends in High Temperatures
Accelerating Temperature Increases
Recent analyses of global temperature data indicate that the highest temperatures of the year have been increasing at an accelerating rate. Over the past 50 years, the global increase was 0.19°C per decade, which accelerated to 0.25°C per decade in the last 30 years. This trend is particularly pronounced in large regions of Eurasia and Australia, where rates exceed 0.60°C per decade. In megacities with populations over 5 million, the average increase is 0.33°C per decade, with some cities experiencing changes higher than 0.60°C per decade2.
Indoor Temperatures and Health
Respiratory and Mental Health
High indoor temperatures have significant health impacts, particularly on respiratory and mental health. Studies have shown that respiratory symptoms worsen in warm indoor environments, with increased respiratory distress calls at temperatures above 26°C. Mental health conditions such as schizophrenia and dementia are also exacerbated by high indoor temperatures. Additionally, the absorption of insulin in people with type 1 diabetes is accelerated in hot indoor environments. Despite these findings, there is insufficient data to establish a precise maximum indoor temperature threshold, though 26°C is suggested as a suitable limit for at-risk groups4.
Mental Health and High Ambient Temperatures
Increased Suicide Risk and Hospital Admissions
High ambient temperatures and heatwaves have been linked to various mental health outcomes. A systematic review identified increased risks of suicide, mental health-related hospital admissions, and emergency department visits at higher temperatures. Specifically, 15 studies reported an increased suicide risk with heat, with relative risks ranging from 1.014 to 1.37 per 1°C increase. However, evidence on the impact of heat on other mental health outcomes remains mixed, highlighting the need for further research5.
Broader Health Risks of Hot Weather
Mortality, Morbidity, and Occupational Health
Hot weather and heat extremes pose significant health risks, including increased mortality and morbidity, adverse pregnancy outcomes, and negative effects on mental health. High heat stress can also reduce physical work capacity and motor-cognitive performance, impacting productivity and increasing the risk of occupational health problems. Nearly half of the global population and over 1 billion workers are exposed to high heat episodes, with about a third experiencing negative health effects. As climate change progresses, heat-related morbidity and mortality are expected to rise, particularly in tropical regions where physiological heat tolerance limits may be regularly exceeded10.
Conclusion
High temperatures have far-reaching impacts on health and the environment, affecting pregnancy outcomes, respiratory and mental health, and increasing the risks of mortality and morbidity. The accelerating trend of rising temperatures, particularly in urban areas, underscores the urgent need for effective heat action plans and further research to mitigate these risks. Addressing the health impacts of high temperatures is crucial for public health, especially in the context of ongoing climate change.
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Most relevant research papers on this topic
Associations between high temperatures in pregnancy and risk of preterm birth, low birth weight, and stillbirths: systematic review and meta-analysis
High temperatures in pregnancy are associated with increased risks of preterm birth, low birth weight, and stillbirths, with larger risks in low and middle income countries.
Meta-Analysis
Rigorous Journal
Highly CitedGlobal, Regional, and Megacity Trends in the Highest Temperature of the Year: Diagnostics and Evidence for Accelerating Trends
The highest temperature of the year has accelerated globally, reaching 0.25°C per decade in the last 30 years, with strong positive trends in Eurasia and Australia, and megacities experiencing higher rates.
Observational StudyHighly CitedHigh temperature reactors
High temperature reactors can enable the production of hydrogen, electricity, and drinking water, offering potential for a sustainable energy source.
Highly CitedIndoor temperature and health: a global systematic review.
High indoor temperatures worsen respiratory health, diabetes management, and core schizophrenia and dementia symptoms, with 26°C being the most suitable temperature for at-risk groups.
Systematic ReviewHighly CitedAssociations between high ambient temperatures and heat waves with mental health outcomes: a systematic review.
High ambient temperatures increase suicide risk, but limited evidence shows an increase in heat-related morbidity and mortality among people with known mental health problems.
Systematic ReviewHighly CitedExtremely High Temperatures
Conference on Extremely High TemperaturesBoston, Massachusetts, March 18–19, 1958. Edited by Dr. Heinz Fischer and Lawrence C. Mansur. (Sponsored by Electronics Research Directorate, Air Force Cambridge Research Center.) Pp. xi + 258. (New York: John Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1958.) 78s. net.
Production and measurement of high temperatures
This paper presents reliable methods for measuring high temperatures in thermally excited plasmas, with potential applications in temperatures exceeding 105 deg K with minor modifications.
The Measurement of High Temperatures
The relationship between temperature and resistance in platinum wire cannot be accurately represented by the Callendar and Griffiths formula, but Heycock and Neville have determined melting points in good agreement using a thermo-couple standardised by direct comparison with the air-thermometer.
Life at High Temperatures
Hot springs provide ideal environments for studying the evolutionary, ecological, and molecular aspects of life at high temperatures, with organisms having evolved to meet environmental challenges.
Highly CitedHot weather and heat extremes: health risks
Heat-related health risks can be prevented with appropriate heat action plans, but climate change and other factors may increase their impact.
Rigorous JournalHighly Cited