Researchers say both too much and too little sleep is linked to a doubled risk of fatal cardiovascular disease.
Teams from the University of Warwick and University College London examined sleep patterns and death rates among 10,308 civil servants.
They found a doubled risk among those who cut their sleeping from seven to five hours a night compared to those who stuck to seven hours a night. But the risk was similar for those who increased to at least eight hours. The research, to be presented to the British Sleep Society, was based on data taken in 1985-88 and on follow up information collected in 1992-93.
The researchers took into account other possible factors such age, sex, marital status, employment grade, smoking status and physical activity. Once they had adjusted for those factors they were able to isolate the effect that changes in sleep patterns over five years had on mortality rates 11-17 years later.
Those who cut their sleeping from seven to five hours a night had twice the risk of a fatal cardiovascular problem of those who stuck to the recommended seven hours a night - and a 1.7 increased risk of death from all causes.
Source - BBC