Researchers said more employers should offer staff the opportunity to have a lie-in a stay and at work later to minimise “psychological stress” that can affect eating and exercise habits.
Mortality rates in "owls",who prefer late nights, are around ten per cent higher than "morning larks", according to the team from the University of Surrey and Northwestern University, Chicago.
This lack of sleep from late nights and early starts at work has previously been shown to increase risk of heart disease and other conditions.
And the new study found mental health disorders and diabetes were most common in night owls and warned sleep deprivation could also fuel unhealthy drinking and drug-taking behaviour.
“This is a public health issue that can no longer be ignored,” said Malcolm von Schantz, professor of chronobiology at the University of Surrey.
“We should discuss allowing evening types to start and finish work later, where practical. And we need more research about how we can help evening types cope with the higher effort of keeping their body clock in synchrony with sun time.”
The study, published in the journal Chronobiology International today, asked more than 433,000 people about their sleeping habits and followed their health over a six and a half years.
In total, 27 per cent of the respondents said they were “definite morning types”, 35 per cent were “moderate morning types” while the proportions for moderate and definite evening types were 28 per cent and nine per cent, respectively.
It found definite morning types tended to be older, were more likely to be women and more likely to be non-smokers. They were also more likely to be non-white, the study found.
Over the study there were 10,534 deaths, roughly 20 per cent due to heart disease, and deaths among "definite evening types" were 10 per cent higher than among the most committed morning people.
The participants health information is tracked as part of the UK Biobank project, and the authors found that even when they statistically controlled for things like smoking, and history of disease, mortality was still higher.
Humans have evolved to be broadly synchronised with the 24-hour day-night cycle on earth, but have individual variation in sleep habits based on a host of genetic and environmental factors, known as a “chronotype”.
There is increasing concern about the disruptive effects of blue light form phone screens and tablets which is similar to daylight.
Sleep disruption has been implicated as a risk factor in things like Alzheimer’s disease, and the researchers said politicians should consider doing away with daylight savings time as the abrupt change has serious health effects at the population level.
“There are already reports of higher incidence of heart attacks following the switch to summer time,” says von Schantz.
“We have to remember that even a small additional risk is multiplied by more than 1.3 billion people who experience this shift every year. I think we need to seriously consider whether the suggested benefits outweigh these risks.”
Kristen Knutson, co-author and associate professor of neurology at Northwestern University Feinberg School of Medicine said recognising that needing a lie in is not a sign of laziness should help guide policy as well.
“Night owls trying to live in a morning lark world may have health consequences for their bodies”
“If we can recognise these chronotypes are, in part, genetically determined and not just a character flaw, jobs and work hours could have more flexibility for owls,” Knutson said.
“They shouldn’t be forced to get up for an 8AM shift. Make work shifts match peoples’ chronotypes.”
The Independent
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