Five per cent of us have a genetic ability to function effectively on less than six hours sleep a night. For the rest of us, sleep deprivation -- sleeping less than seven and a half hours a night -- leads in the short term to a loss of effectiveness and in the longer term to serious health problems such as an increased risk of high blood pressure and cancer.
It even manifests as a higher risk of mortality among shift workers. Unfortunately, the relentlessness and stresses of modern life put pressure on our ability to get a good night's sleep.
So, how can we ensure we get enough sleep? Oz recommends that people set their alarm clocks not for when they want to wake up, but seven and a half hours earlier, to remind them to go to bed and have the opportunity of a full sleep quota. And switch off those mobile phones.