By the end of this century, hotter nights could cost the average person roughly 16 hours of sleep a year, and the children set to lose the most rest are concentrated in the regions least able to cool down. That estimate comes from a new analysis in Nature Sustainability that traces an uncomfortable chain of cause and effect from a warm bedroom all the way to a smaller paycheck decades later.

Warmer nights shorten sleep. Less sleep in childhood blunts cognitive development. Weaker cognitive development drags on lifetime earnings. Tallied across the globe under a high-emissions scenario, the researchers put the price of all that lost sleep in the trillions of dollars, with the heaviest burden falling on countries that contributed least to the warming. The effect on any one child is small. The aggregate, and the way it widens the gap between rich and poor regions, is the story.

From a hot night to a smaller paycheck

The study, led by Bowen Chu and colleagues at Nanjing University, links together three relationships that other researchers had already documented separately: how temperature affects sleep duration, how childhood sleep affects measured IQ, and how IQ tracks with lifetime economic productivity. Chaining them together produces a single projection that describe what a warming climate could do to human capital in the aggregate and individual earning potential for future generations.

Measured against a 2001–2010 baseline, and assuming people make no effort to adapt, excess sleep loss reaches about 16.4 hours per person per year by the 2100s under the highest-emissions pathway, which could warm the world 2.4°C by 2060; the equivalent of erasing roughly two full nights of sleep over the course of a year. The largest projected impacts cluster in southern and eastern Africa and southern and eastern Asia.

From there, a commentary accompanying the study lays out the downstream impact. The average per-person loss of IQ could be about 0.026 points in high-income settings and 0.058 points in lower-income ones. While that may seem modest at the individual level, which considered alongside a global economic cost due to lost intelligence on the order of $2.86 trillion in the 2100s, the consequences of a warming world are dire.

The research is an attempt to quantify a cascading series of impacts that, if no effort to reduce global warming takes place, will come to pass; it is not a forecast set in stone.

Why heat robs you of rest

To fall asleep and stay there, your core body temperature has to drop, and it keeps falling to a low point in the early hours of the morning, in step with your circadian rhythm. A warm room blocks that decline, and the brain struggles to reach its deepest, most restorative stages. As Cleveland Clinic sleep specialist Michelle Drerup has put it, “Heat is a huge disruptor for REM sleep.”

The damage isn’t shared evenly. The research consistently finds that older adults, women, people in lower-income countries, and those already living in hot climates lose the most sleep when nights warm. These are the same groups that tend to have the fewest resources to cool down.

The cooling trap

The obvious fix is air conditioning, and the study’s “no adaptation” assumption is where reality gets complicated. Yes, AC keeps bedrooms cool, but where the electricity is generated from fossil fuels it adds to the emissions driving the warming, and the refrigerants inside many units are themselves potent greenhouse gases. AC is also least available in the lower-income, hotter regions the study flags as most exposed.

That is the uncomfortable core of the finding. Adaptation strategies exist, but they are unevenly distributed, and the cheapest, most universal lever is the one that shrinks the problem at its source by reducing atmospheric CO₂ levels. The 16-hour figure is tied to a high-emissions future; lower-emissions pathways bend the curve down. The harm, in other words, is partly a choice.

What You Can Do

For a cooler night’s sleep, starting tonight:

• Aim cool. Sleep guidance generally points to a bedroom around 65°F as the sweet spot, within a band most experts place between roughly 60 and 68°F.
• Block the day’s heat. Close curtains and blinds against direct sun, and keep windows shut when it’s hotter outside than in. Sunlight both warms the room and suppresses the melatonin that helps you drift off.
• Flush heat at night. When the outside air finally cools, open up and cross-ventilate with one fan pushing hot air out a window, another drawing cooler air in. A bowl of ice in front of a fan is a low-tech way to chill the breeze.
• Take a warm shower one to two hours before bed. It sounds backward, but passive body heating triggers the blood-vessel dilation that sheds core heat afterward. A 2019 meta-analysis found a 10-minute warm bath or shower of about 104–108°F, timed one to two hours before bed, shortened the time it took to fall asleep. In extreme heat, a lukewarm rinse is easier to tolerate and still helps you cool off.
• Go breathable, and go low. Lightweight cotton bedding and sleepwear beat heat-trapping synthetics. Heat rises, so a lower floor or a mattress closer to the ground will help you sleep cooler.

For your home and your footprint:

• Reach for fans, shading, and insulation before the air conditioner, and keep any AC you do run efficient — right-sized, well-maintained, and turned down when nights allow.
• Lean on low-tech cooling strategies during milder stretches so cooling energy is reserved for the genuinely dangerous days.

In youe community:

• Support community cooling centers and urban tree canopy and heat-island reduction, which protect the people who have no home cooling at all — the same groups the research identifies as most exposed.
• Keep the scenario in view. The projected harm scales with emissions, so the most effective response to lost sleep at the population level is the same one that addresses heat itself: cutting carbon fast enough to keep the high-warming pathway from arriving.

Related Reading

• Heat Wave Health Risks: Safety Tips for Extreme Heat
• Climate Crisis: Keeping Cool Without Air Conditioning
• Cutting the Climate Impact of Your Air Conditioner

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