Researchers from Semmelweis University in Hungary analysed data from over 2.1 million people and found those who slept fewer than seven hours had a 14 per cent higher risk of death, while those who slept more than nine hours faced a 34 per cent increase.

Men were more affected by short sleep, while long sleep carried greater risk for women, raising their chance of death by 44 per cent. 

"Even though awareness has grown, our behaviour hasn’t changed much in the last decade," said Dr Gyorgy Purebl, co-author of the study.

A second analysis linked both short and long sleep to increased stroke risk and mortality. Those sleeping more than eight hours had a 46 per cent higher stroke risk and were 45 per cent  more likely to die from it.

“Sleep duration should be considered in stroke prevention strategies,” said senior author Dr Balazs Gyorffy.