PEOPLE who are chronically jet lagged or sleep deprived are likely to die younger. This warning was imparted by bleary-eyed researchers at an early morning session of the EuroScience Open Forum recently.
Alexis Webb, a neuroscientist-turned-science communicator, pointed to a 2006 study that showed chronically sleep-derived mice lived substantially shorter lives than mice that had a normal and uninterrupted sleep.
One reason is because the sleep deprived are at greater risk of injuring themselves: on less sleep people have slower response times and are likely to be less accurate when they act or make a decision.
This phenomenon is — very worryingly — exemplified by cabin crew, who are often jet lagged and have permanently confused body clocks. In 2000, a study found that cabin crew had more delayed response times than airline ground staff, and impaired spatial cognition.
"Cabin crew also exhibited cognitive deficits, possibly in working memory, that became apparent after several years of chronic disruption of circadian rhythms," the authors of the study wrote. This became worse the more years that the cabin crew were chronically sleep deprived.
The research also has implications for frequent travellers, people who habitually burn the midnight oil, and shift workers. But a compelling reason for the increased risk of mortality in the chronically sleep deprived is that it disrupts their entire body. People who lack regular and adequate sleep are more at risk of several diseases, including obesity, heart disease and hypertension.
The night-time environment is fundamentally different to the day, which seems obvious, but is often forgotten in an age of light pollution and a social media that never sleeps.
From the days when early human ancestors sought shelter to hide from the predator-filled night and hunted and gathered only when it was light enough to see, human bodies have adapted different physiological responses to these environments: from the production of stress hormones, body temperature, mood, and blood pressure, through to sleep.
"We thought that the brain clock was the only clock in the body," says Akhilesh Reddy, a neuroscientist and senior group leader at the Francis Crick Institute in London. "But every tissue has its own intrinsic body clock: liver, muscles, fat, brain."
Even if those cells were removed from people’s bodies, they would still oscillate with 24-hour behaviour. All of these layers communicate with each other and for a body to function optimally, they all need to resonate — something that is impossible for people who alternate between night-and day-shifts, or who are chronically sleep deprived.
Human metabolism is closely linked with this internal clock. "In circadian synchronicity, you eat and sleep when you should," Reddy says. "If you experience circadian asychronicity, then you disrupt the links between the different layers, and this leads to metabolic consequences."
One example, he says, is that when some people adjust to jet lag, their bodies handle glucose — the sugars in their blood — as though they were diabetic, even if they are not.
Webb highlighted a 2012 study that found a link between when people ate and their weight. Researchers at the Salk Institute for Biological Studies in the US found that putting mice on a high fat, but time-restricted diet — in which they were allowed to eat only in an eight-hour window — reduced their body fat, inflammation and glucose intolerance, among a number of other markers. A similar study was undertaken on a small sample of people, in which their eating was restricted to a 10-to 12-hour window period for 16 weeks.
"There was no advice on calories or nutrition", Webb says. "Just a window of eating, and they reduced body weight and improved … sleeping."
But in modern life, people no longer have the solar cues guiding their sleep. Human bodies are effectively a large clock, and it is set to the outside world through people’s eyes, says Russell Foster, a professor of circadian neuroscience at the University of Oxford. "Our eyes not only provide us with a sense of place, but also a sense of time," he says.
This makes it difficult for the visually impaired to set their internal clocks — but not for all forms of blindness. Inside the eyes, there are cells called intrinsically photosensitive retinal ganglion cells, which are the main conduit of information for a body’s circadian network. So, while someone may be visually impaired and unable to see, if these cells are intact, then they will set the person’s body clock.
Unfortunately for people with a smartphone addiction, these cells are most sensitive to blue light, which is what electronic devices emit. When people wake up in the middle of the night and reach for their phone, its light signals to their brains and bodies that it is time to wake up.
"Our alertness is profoundly affected by light," Foster says. But some people spend their lives in a constant dimness, even at night when they should — for the sake of a good night’s sleep — be in complete darkness. "The only time we’re in darkness is when we sleep — and that’s an output, not an input."
The converse is true of millions of people’s day-time lives: when they should be getting a lot of light and be alert and awake, they’re stuck in dimly lit offices.
For full alertness, people need about 800 LUX, says Foster. LUX is a measure of luminescence. From about one metre away from a candle, a person is exposed to one LUX. Outside in full sun, the LUX is about 100,000.
An average office is about 400 LUX; this is determined in large part by computer screens, which need to be operated in a fairly dim environment.
An average office worker is, therefore, only half awake.
• Wild attended the EuroScience Open Forum courtesy of a Nature Travel Grant
When people wake up in the middle of the night and reach for their phone, its light signals to their brains and bodies that it is time to wake up. Picture: ISTOCK
PEOPLE who are chronically jet lagged or sleep deprived are likely to die younger. This warning was imparted by bleary-eyed researchers at an early morning session of the EuroScience Open Forum recently.
Alexis Webb, a neuroscientist-turned-science communicator, pointed to a 2006 study that showed chronically sleep-derived mice lived substantially shorter lives than mice that had a normal and uninterrupted sleep.
One reason is because the sleep deprived are at greater risk of injuring themselves: on less sleep people have slower response times and are likely to be less accurate when they act or make a decision.
This phenomenon is — very worryingly — exemplified by cabin crew, who are often jet lagged and have permanently confused body clocks. In 2000, a study found that cabin crew had more delayed response times than airline ground staff, and impaired spatial cognition.
"Cabin crew also exhibited cognitive deficits, possibly in working memory, that became apparent after several years of chronic disruption of circadian rhythms," the authors of the study wrote. This became worse the more years that the cabin crew were chronically sleep deprived.
The research also has implications for frequent travellers, people who habitually burn the midnight oil, and shift workers. But a compelling reason for the increased risk of mortality in the chronically sleep deprived is that it disrupts their entire body. People who lack regular and adequate sleep are more at risk of several diseases, including obesity, heart disease and hypertension.
The night-time environment is fundamentally different to the day, which seems obvious, but is often forgotten in an age of light pollution and a social media that never sleeps.
From the days when early human ancestors sought shelter to hide from the predator-filled night and hunted and gathered only when it was light enough to see, human bodies have adapted different physiological responses to these environments: from the production of stress hormones, body temperature, mood, and blood pressure, through to sleep.
"We thought that the brain clock was the only clock in the body," says Akhilesh Reddy, a neuroscientist and senior group leader at the Francis Crick Institute in London. "But every tissue has its own intrinsic body clock: liver, muscles, fat, brain."
Even if those cells were removed from people’s bodies, they would still oscillate with 24-hour behaviour. All of these layers communicate with each other and for a body to function optimally, they all need to resonate — something that is impossible for people who alternate between night-and day-shifts, or who are chronically sleep deprived.
Human metabolism is closely linked with this internal clock. "In circadian synchronicity, you eat and sleep when you should," Reddy says. "If you experience circadian asychronicity, then you disrupt the links between the different layers, and this leads to metabolic consequences."
One example, he says, is that when some people adjust to jet lag, their bodies handle glucose — the sugars in their blood — as though they were diabetic, even if they are not.
Webb highlighted a 2012 study that found a link between when people ate and their weight. Researchers at the Salk Institute for Biological Studies in the US found that putting mice on a high fat, but time-restricted diet — in which they were allowed to eat only in an eight-hour window — reduced their body fat, inflammation and glucose intolerance, among a number of other markers. A similar study was undertaken on a small sample of people, in which their eating was restricted to a 10-to 12-hour window period for 16 weeks.
"There was no advice on calories or nutrition", Webb says. "Just a window of eating, and they reduced body weight and improved … sleeping."
But in modern life, people no longer have the solar cues guiding their sleep. Human bodies are effectively a large clock, and it is set to the outside world through people’s eyes, says Russell Foster, a professor of circadian neuroscience at the University of Oxford. "Our eyes not only provide us with a sense of place, but also a sense of time," he says.
This makes it difficult for the visually impaired to set their internal clocks — but not for all forms of blindness. Inside the eyes, there are cells called intrinsically photosensitive retinal ganglion cells, which are the main conduit of information for a body’s circadian network. So, while someone may be visually impaired and unable to see, if these cells are intact, then they will set the person’s body clock.
Unfortunately for people with a smartphone addiction, these cells are most sensitive to blue light, which is what electronic devices emit. When people wake up in the middle of the night and reach for their phone, its light signals to their brains and bodies that it is time to wake up.
"Our alertness is profoundly affected by light," Foster says. But some people spend their lives in a constant dimness, even at night when they should — for the sake of a good night’s sleep — be in complete darkness. "The only time we’re in darkness is when we sleep — and that’s an output, not an input."
The converse is true of millions of people’s day-time lives: when they should be getting a lot of light and be alert and awake, they’re stuck in dimly lit offices.
For full alertness, people need about 800 LUX, says Foster. LUX is a measure of luminescence. From about one metre away from a candle, a person is exposed to one LUX. Outside in full sun, the LUX is about 100,000.
An average office is about 400 LUX; this is determined in large part by computer screens, which need to be operated in a fairly dim environment.
An average office worker is, therefore, only half awake.
• Wild attended the EuroScience Open Forum courtesy of a Nature Travel Grant
