'Arrogance' of ignoring need for sleep
Society has become "supremely arrogant" in ignoring the importance of sleep, leading researchers have told the BBC's Day of the Body Clock.
Scientists from Oxford, Cambridge, Harvard, Manchester and Surrey universities warn cutting sleep is leading to "serious health problems".
They say people and governments need to take the problem seriously.
Cancer, heart disease, type-2 diabetes, infections and obesity have all been linked to reduced sleep.
The body clock drives huge changes in the human body.
It alters alertness, mood, physical strength and even the risk of a heart attack in a daily rhythm.