A new study examines the damaging impact of global warming on sleep.
Climate change could affect your sleep - and not just because you’re lying awake worrying about it.
A new study shows that warmer temperatures heighten the risk of insufficient sleep.
As global warming worsens, so will our ability to get a good night’s sleep, according to researchers - adding to the mental health toll of our heating planet.
How does climate change impact sleep?
You’ve probably experienced trouble sleeping when it’s too hot. Now there’s data that shows you're not alone.
Comparing local weather with sleep tracking data from wristbands, researchers led by Kelton Minor at the University of Copenhagen, Denmark found that warmer nighttime temperatures do indeed harm sleep.
Researchers gathered over 7 million nighttime sleep records from more than 47,000 people in 68 countries between 2015 and 2017.
Controlling for individual factors, seasonal and time trends, they found that elevated temperatures shorten sleep - primarily by lengthening the time it takes to get to sleep.
On very warm nights - with temperatures over 30°C - they found that people sleep an average of 14 minutes less. The probability of sleeping less than seven hours increases gradually up to 10°C, before increasing at an elevated rate.
If we keep emitting greenhouse gases at the current rate, by 2100 each person could each face an average of two weeks of temperature-related short sleep - or between 50 and 58 hours of sleep loss - per year, researchers found.
People are already losing around 44 hours of sleep per year due to higher temperatures this century, they estimate.
The study was published this month in peer-reviewed science journal One Earth.
Why is sleep deprivation dangerous?
A lack of shuteye can make you moody - but prolonged periods of sleep deprivation carry far more sinister consequences.
Previous studies have shown that insufficient sleep can impact you both mentally and physically. It has been linked to reduced cognitive performance and productivity as well as depression and anger.
A lack of sleep could also reduce your immune function, cause hypertension and heart problems, increase the risk of accidents and accelerate ageing.
Who is most at risk of climate-related sleep deprivation?
Not everyone is impacted equally by the effects of warmer temperatures on sleep.
Researchers found that the elderly, residents of lower-income countries, women, and those already living in hotter climates are disproportionately impacted. This is likely to widen existing global inequalities.
Temperatures are increasing worldwide, with the greatest increases recorded at night. Climate change and the expansion of urban heat islands are both contributing to this.
Those in hotter regions were found to experience more sleep loss per degree of warming. This suggests that human ability to adapt to hotter weather is limited.
Comparing sleep loss data with NASA global climate projections, they created a world map of risk. It shows that those in Asia, Australia and the Middle East will be most affected by climate-related sleep loss in the coming years.
What is the ideal temperature for sleep?
The ideal temperature for sleep is around 16 to 20°C. Your body regulates your internal temperature as you sleep, but higher external temperatures make this more difficult - especially for elderly people.
Those in wealthier countries are more likely to have air conditioning to help them obtain an optimal sleeping temperature - but this is a vicious cycle.
Air conditioners use more electricity than any other appliance in the home, producing emissions and leaking planet-warming chemicals. While in some countries air con is a life saving essential, in milder climates it is often more of a luxury.
As we edge ever closer to critical warming limits, it has never been more important to curb emissions.
Placing stricter regulatory standards on air con units, maximising trees and green space, and positioning buildings to maximise shade and ventilation can all help lower the impact and use of air con.