Bosses should consider providing nap rooms for employees and not expect them to answer emails after hours, according to a new report into the effects of sleep deprivation on productivity.

Workers who don’t turn up because they are exhausted or ill through lack of sleep – or those who do come to work but are tired and sluggish – cost the UK $50 billion (£40 billion) a year, found the study.

Researches at global policy think tank Rand analysed recent survey data from 62,000 people in five countries: the US, Japan, the UK, Germany and Canada.

They found employees who sleep less than six hours a night lose around six more working days through absenteeism or presenteeism each year than those who sleep seven to nine hours a night.

Marco Hafner, the lead author of the study, told The Independent while some companies, especially newer ones, provide their employees with support and advice on how to get a good night’s sleep, most did not do enough.

“The average company is probably not aware of the issues [around sleep deprivation]. It should become a normal part of the office, for instance having a nap room,” he said.

“Small companies might not have the facilities, but there are other things employers can do, like getting sleep into the culture of the company.”

Mr Hafner said employers should encourage workers to switch off electronic devices when they are not at work, “so they can take some sleep instead of looking at emails at 11pm.”

More than one third of the UK population regularly gets less than six hours of sleep a night, according to the British Sleep Council.

Sleep deprivation can increase the risk of obesity, heart disease and diabetes, and raises the risk of an early death by 12 per cent, Sleep Council researchers warned last year.

And scientists at Surrey University found more than 700 of the body’s genes, including those that govern the immune system, are altered if someone sleeps less than six hours a night.

Rand calculated that relative to the size of each country's economies, Japan had the greatest drop in productivity due to sleep deprivation, with an annual loss of $138 billion (£110 billion) – 2.9 per cent of its GDP.

The US, where lack of sleep has been declared a public health problem by the Centre for Disease Control and Prevention, came second, with an estimated loss of 2.3 per cent of its GDP, or $411 billion (£329 billion).

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And the UK was deemed worse than Germany and Canada for the amount lost through sleep deprivation, which was estimated at 1.9 per cent of GDP compared to 1.6 per cent in Germany and 1.4 per cent in Canada.

Mr Hafner said he and his team had observed a “cultural issue” in the UK and other countries of boasting over lack of sleep.

“Sometimes the company leader, the CEO, says: ‘I’m getting four hours of sleep and I’m fine’,” he said. “But I’m sure if that CEO slept more than four hours, he’d be more productive.”