Lack of sleep linked to early death: study

People who get less than six hours sleep per night have an increased risk of dying prematurely, researchers said on Wednesday.

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," Francesco Cappuccio, who led research on the subject at Britain's University of Warwick, told AFP.

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.

"We think that the relation between little sleep and illness is due to a series of hormonal and metabolical mechanisms," Cappuccio said.

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

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

"Society pushes us to sleep less and less," Cappuccio said, adding that about 20 percent of the population in the United States and Britain sleeps less than five hours.

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 Cappuccio said oversleeping is more likely to be an effect of illness, rather than a cause.

"Doctors never ask how much one sleeps, but that could be an indicator that something is wrong," said Cappuccio, who heads the Sleep, Health and Society Programme at the University of Warwick.

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