How climate change will affect how much sleep we get

By Stephen Beech via SWNS

Climate change means people will be getting less SLEEP due to soaring temperatures, according to a new study from Denmark.

The research suggests that people will enjoy up to 10 minutes less slumber per night as a result of global warming by the end of the century.

They found that increasing ambient temperatures negatively impact human sleep around the globe as they get their head down later, but wake up earlier.

The team says their findings suggest that by the year 2099, suboptimal temperatures may erode 50 to 58 hours of sleep per person per year.

They also found that the temperature effect on sleep loss is "substantially larger" for residents from lower income countries as well as in older adults and females.

Study first author Kelton Minor said: “Our results indicate that sleep - an essential restorative process integral for human health and productivity - may be degraded by warmer temperatures.

“In order to make informed climate policy decisions moving forward, we need to better account for the full spectrum of plausible future climate impacts extending from today's societal greenhouse gas emissions choices.”

He said that it's long been known that hot days increase deaths and hospitalizations and worsen human performance, yet the biological and behavioral mechanisms underlying these impacts have not been well understood.

Recent data from the United States has suggested that subjective sleep quality decreases during periods of hot weather.

But how temperature fluctuations may impact changes in sleep patterns in people living across a variety of global climates has remained unclear.

Mr. Minor, a doctoral student at the University of Copenhagen in Denmark, said: "In this study, we provide the first planetary-scale evidence that warmer-than-average temperatures erode human sleep.

“We show that this erosion occurs primarily by delaying when people fall asleep and by advancing when they wake up during hot weather.”

The research team used anonymized global sleep data collected from accelerometer-based sleep-tracking wristbands. The figures included seven million nightly sleep records from more than 47,000 adults in 68 countries spanning all continents except for Antarctica.

Measures from the type of wristbands used in the study had previously been shown to align with independent measures of wakefulness and sleep.

The study, published in the journal One Earth, suggested that on very warm nights - greater than 30 degrees Celsius, or 86 degrees Fahrenheit - sleep declines an average of just over 14 minutes. The likelihood of getting less than seven hours of sleep also increases as temperatures rise.

Mr. Minor said: “Our bodies are highly adapted to maintain a stable core body temperature, something that our lives depend on.

“Yet every night they do something remarkable without most of us consciously knowing - they shed heat from our core into the surrounding environment by dilating our blood vessels and increasing blood flow to our hands and feet.”

In order for our bodies to transfer heat, the surrounding environment needs to be cooler than we are.

Previous lab studies found that both humans and animals don't sleep as well when the room temperature is too hot or too cold. But the research was limited by how people act in the real world: they modify the temperature of their sleeping environment to be more comfortable.

In the current research, the investigators found that under normal living routines, people appear far better at adapting to colder outside temperatures than hotter conditions.

Mr. Minor added: “Across seasons, demographics, and different climate contexts, warmer outside temperatures consistently erode sleep, with the amount of sleep loss progressively increasing as temperatures become hotter."

One important observation was that people in developing countries seem to be more affected by the changes, which may be down to the greater prevalence of air conditioning in developed countries.