Adam Vaughan is a writer.
Many people have trouble sleeping.
Stock-Asso.
People are losing sleep over climate change. A global study has found that a warming planet is affecting how long people sleep, and the problem will get worse this century even if humanity manages to rein in its carbon emissions.
The impact of night temperatures on sleep has previously been limited by being limited to single countries, lab studies or unreliable self-reporting.
Kelton Minor at the University of Copenhagen took data from sleep-tracking wristbands used by 48,000 people in 69 countries between 2015 and 2017.
He and his colleagues found out that hot nights are causing people to fall asleep later, rise earlier and sleep less. Evidence shows that people lose 44 hours of sleep each year. If emissions go unaddressed, people will lose 58 hours of sleep a year. The figure drops to 50 hours in a lower-emissions future.
Minor and his team measured the level of sleep loss on hot nights by comparing the data with a baseline of how much an individual sleeps normally. The weather and the season are possible explanations for sleep erosion.
This is the first evidence that warmer-than-average temperatures erode sleep. Minor says they show that sleep erosion occurs when people fall asleep.
Some groups are hit worse than others. People in lower-income countries have a larger impact on sleep loss at night because of the heat. The effect on sleep of an increase in the minimum overnight temperature was twice that of younger age groups.
The researchers found that people didn't change their behavior to cope with the lack of sleep. People didn't adapt by finding it easier to sleep on a warm night at the end of summer than on a warm night early in summer.
It is possible that people living in higher-income countries are more likely to install air conditioning, which is seen as a form of adaptation, but Minor says the findings in the study don't allow him to make a conclusive link. Air conditioning's cost makes it out of reach for many and it can drive up emissions due to fossil fuel energy use.
The study's methodology is sound and includes a thorough examination of other explanations. She says that since we know that lack of sleep can negatively impact mood, behavior, health and cognitive functioning, this is concerning.
The study shows the power of big data and is in line with previous work showing the better people sleep. The measured effect is small, just minutes of sleep per night, or less than 3% of total sleep time.
Minor believes that the type of person who chooses to wear a sleep-tracker may be more likely to have access to other technologies that can help them sleep. The team's estimates of climate change's impact on sleep are likely to be low.
One Earth is a journal.
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