Over-sleepers seem to be at greater risk; those who constantly sleep more than eight hours run a 33 per cent increased risk for cardiovascular disease. Those who sleep less than six hours have a 11 per cent higher risk.
But the occasional bad night-sleep isn't going to make a big difference. The researchers tracked the sleeping habits of more than 1 million people for over nine years, and who were divided into three groups of under-sleepers, over-sleepers and those sleeping between six and eight hours every day.
Researchers from the Onassis Cardiac Surgery Centre in Athens say they aren't sure why sleep should influence health but think it may have something to do with glucose metabolism, blood pressure and inflammation.
"Having the odd short night or lie-in is unlikely to be detrimental to health, but evidence is accumulating that prolonged nightly sleep deprivation or excessive sleeping should be avoided," said lead researcher Dr Epameinondas Fountas.
Regular sleeping habits and avoiding caffeine and alcohol before bed, having a healthy diet and regular exercise can all help achieve the sleeping sweet spot, the researchers say.