The risk of death from excessively hot nights could increase nearly six-fold by the end of the century, according to a new study published in The Lancet Planetary Health.
Sweltering nights may interrupt the normal physiology of sleep. A disrupted sleeping pattern can damage the immune system and lead to a higher risk of cardiovascular disease, chronic illnesses, inflammation and mental health conditions, findings of the study warned.
The study, published August 8, 2022, was co-authored by a group of researchers from China, South Korea, Japan, Germany and the United States.
The team estimated mortality due to excess heat in 28 cities in China, South Korea and Japan between 1980 and 2015 and applied it to the climate change models adapted by the respective national governments.
“The risks of increasing temperature at night were frequently neglected,” said Yuqiang Zhang, a climate scientist in the department of environmental sciences and engineering at the Gillings School of Global Public Health, University of North Carolina.
The risk of death from excessively hot nights will increase the mortality rate worldwide by up to 60 per cent by 2100, the scientists estimated. This prediction is much higher than the mortality risk from daily average warming suggested by current climate change models.
“While assessing the disease burden due to non-optimum temperature, governments and local policymakers should consider the extra health impacts of the disproportional intra-day temperature variations,” said Haidong Kan, a professor at Fudan University in China.
Regional differences in temperature accounted for many of the variations in nighttime temperature, the scientists noted.
Areas with the lowest average temperature are estimated to have the largest warming potential, they added.
“To combat the health risk raised by the temperature increases from climate change, we should design efficient ways to help people adapt,” Zhang added.
The scientists advocated for the adoption of more robust mitigation strategies, including global collaborations, to reduce future impacts of warming.
“Heat during the night should be considered when designing the future heatwave warning system, especially for vulnerable populations and low-income communities who may not be able to afford the additional expense of air conditioning,” Zhang added.