But most business-class beds aren't wide enough for deep sleep because passengers can't change positions without waking up.

WSJ: The Many Ways to Catch Shut-Eye in the Sky

That part of the brain is essential for entering deep sleep, but with age the region degrades.

BBC: Boosting sleep 'may slow memory rot'

When you need to take a break, close the lid and VAIO goes into an energy-efficient deep sleep, keeping your data stored safely for up to 90 days1 without running out of power.

ENGADGET: Sony announces its first Ultrabooks, the VAIO T13 and T11, for the European market

Total deep sleep decreases from nearly 20% of a normal nights sleep for those under 25 to less than 5% for those over 35.

BBC: Sleep linked to ageing

It took a long time for the disposal squad to make the bomb safe and during that time, the Ross family had to sleep deep down, on the platforms of Southgate Tube station.

BBC: Stanley Ross remembers the Blitz