Hotter nights could increase mortality rates, a study warns

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A man wearing a face mask walks along a shopping street on March 25, 2022 in Tokyo, Japan. Carl Court/Getty Images hide caption

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Carl Court/Getty Images

A man wearing a face mask walks along a shopping street on March 25, 2022 in Tokyo, Japan.

Carl Court/Getty Images

Rising nighttime temperatures may increase the mortality rate up to 60% across three countries by the end of the century, according to a study whose authors say is the first research to estimate the impact of hotter nights on climate change-related mortality risks.

That mortality rate focuses on deaths from excessively hot nights. More heat at night can disrupt sleep patterns as the body attempts to cool down, leading to adverse effects on the immune system. This could contribute to the probability of developing cardiovascular disease, chronic illnesses, inflammation and mental health challenges, the authors of the study concluded.

By 2090, the hot night excess — which measures the excess night temperature above a typical threshold — could double across 28 cities across China, Japan and South Korea, according to the research.

"To combat the health risk raised by the temperature increases from climate change, we should design efficient ways to help people adapt," said Dr. Yuqiang Zhang, a climate scientist at the University of North Carolina-Chapel Hill and an author of the study. "Locally, heat during the night should be taken into account 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."

However, Zhang warns against applying the study's results to the rest of Asia and other regions across the globe as he and other authors of the study have not yet analyzed global data.

The study was co-authored by a group of researchers in China, South Korea, Japan, Germany and the United States.