Health·Second Opinion

Night owls face higher risk of premature death, study says

New research that suggests "night" people have a higher risk of a premature death compared to morning folks.

Do you get up early or stay up late? Your sleep habits could make a big difference

Researchers suspect there are potentially dangerous physiological changes caused by circadian imbalance and 'social jet lag' — when your body's clock is out of step with the outside world. (Shutterstock)

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What's your chronotype? Do you lean toward "morningness" or "eveningness?" It matters, according to new research that suggests "night" people have a higher risk of early death compared to morning folks.

The researchers followed almost half a million U.K. adults for six years and after adjusting for age and other health risks still found that the "night owls" had a 10 per cent higher risk of death over that six years.

You have more opportunity… to engage in these unhealthy behaviours- Kriston Knutson, sleep researcher

The findings didn't appear to be based simply on a lack of sleep. The "evening chronotypes" reported getting as much sleep as the morning chronotypes.

The researchers suspect there are potentially dangerous physiological changes caused by circadian imbalance and "social jet lag" — when your body's clock is out of step with the outside world.

"If you're not doing [activities] at the time that your body is expecting, that can lead to this circadian misalignment — that your internal clock and the external world do not agree about what time it is," said Kristen Knutson, a sleep researcher at Chicago's Northwestern University.

She points to experiments that deliberately interrupt people's circadian rhythms resulting in distinct biochemical responses including increased blood pressure, decreased insulin sensitivity, increased inflammation and other factors that can cause disease.

Part of the explanation might be that night owls have unhealthy habits.

"If you're up late in the dark you have more opportunity or perhaps occasion to engage in these unhealthy behaviours like drinking or drug use," said Knutson. But, she said, research suggests there's something else going on.

"It's this mismatch between their internal system and the external world and the irregularity in their schedule that might be causing the problem."

It's the latest in a series of studies suggesting that making everyone conform to the same time schedule could have important public health implications.

Activity at unusual times of the day might lead to misalignment between your internal clock and the outside world, according to researchers. (Darryl Webb/Reuters)

'Win-win' in the workplace

And for people who have evening chronotype circadian rhythms, the challenges begin with the first days of school.

This week another study concluded that letting students in Singapore start school a little bit later improved their "alertness and mental well-being."

The same impact was observed in Canada where it's estimated that up to a third of Canadian children and teenagers are not getting the recommended amount of sleep, partly because they have to get up so early for school.

For every half an hour of later school start time, there's a benefit for kids.- Genevieve Gariepy, epidemiologist

Using data from students at more than 360 Canadian schools with start times ranging between 8 a.m. to 9:30 a.m. researchers concluded that students from schools with later start times were "more likely to meet sleep recommendations and were less likely to report feeling tired in the morning."

"For every half an hour of later school start time there's a benefit for kids," said study author Genevieve Gariepy, an epidemiologist at McGill University.

When her research paper was released last year it topped, for a while, the most-read list on the social media site Reddit. 

"I think everybody's really interested but of course there are major structural barriers. The number one thing it seems is bus schedules."

A few Canadian schools have experimented with later start times, but despite evidence that it improves student performance, most school start times have not changed.

"I think there's still some social pushback," said Gariepy. "Some people might say 'Teenagers need to wake up early because they need to get used to real life,' but we don't say that to little kids — 'No napping, you have to get used to real life.' It's biology."

Can a night owl change into a morning "lark?" By sticking to a strict routine and gradually going to bed earlier, Knutson said they might be able to change their chronotype.

But should they be forced to change? Or should society try to accommodate different chronotypes?

"It certainly is a real thing and I would like employers to be more aware of the variability between individuals in their timing preferences," she said. "It could be important for productivity, so it could be a win-win for employer and employee when flexible schedules are possible."

"Everybody knows that losing sleep is bad for you but we don't know much about the specifics of that," said Adrian Owen, a Western University neuroscientist who is running the world's largest sleep study, where researchers have gathered sleep and cognition data from more than 100,000 people.

Their early data suggests there are individual variations in sleep needs.

"It does seem as though for every individual person there is an amount of sleep you should try to aim for," Owen said..

A teacher addresses schoolchildren in Singapore, in April 2003. Another recent study concluded that letting students in Singapore start school a little bit later improved their 'alertness and mental well-being.' (David Loh/Reuters)

Leaders need sleep too

One preliminary hint from the sleep study: Despite claims from some prominent world leaders that they can run a country on four hours of sleep, Owen's early analysis suggests it's unlikely.

"We looked for fun at the people who claimed to get by on four hours sleep and compared them to people who had the optimal average amount of sleep [7.6 hours]. On every single cognitive measure the four-hour people were impaired," Owen said. "This is reasoning, it's problem solving, it's their ability to remember information for short periods of time."

"I would venture it isn't true that you can run a country effectively on four hours sleep," said Owen.

"I wouldn't say you can't do it, but I don't think you could do it as well as you could do it if you were getting a bit more sleep."

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Kelly Crowe

Medical science

Kelly Crowe is a health and science reporter, who previously spent more than 30 years reporting on a wide range of national news and current affairs for CBC News.