i saw tis article in the yahoo webside.i found that it is intersting cause it's a close topic to me,so i just hv a look on it.

People who get less than six hours sleep per night have an increased risk of dying prematurely.Those who slumbered for less than that amount of time were 12 percent more likely to die early, though researchers also found a link between sleeping more than nine hours and premature death.

If you sleep little, you can develop diabetes, obesity, hypertension and high cholesterol .The study, conducted with the Federico II University in Naples, Italy, aggregated decade-long studies from around the world involving more than 1.3 million people and found "unequivocal evidence of the direct link" between lack of sleep and premature death.

they think that the relation between little sleep and illness is due to a series of hormonal and metabolical mechanisms.

The findings of the study were published in the Sleep journal.

the duration of sleep is a public health issue and should be considered as a behavioural risk factor by doctors.

Sleeping less than six hours is "more common amongst full-time workers, suggesting that it may be due to societal pressures for longer working hours and more shift work".

The study also found a link between sleeping more than nine hours per night and premature death, but oversleeping is more likely to be an effect of illness, rather than a cause.

Research showed no adverse effects for those sleeping between six and eight hours per day.