Study on Sleep Duration and Mortality

We all know that getting too little sleep is bad. You feel tired, you may be irritable, and it can contribute to obesity, high blood pressure, diabetes, and heart disease, doctors say. But too much sleep? You don't often hear people complaining about it.

However, research carried out over the past 10 years appears to show that adults who usually sleep for less than six hours or more than eight, are at risk of dying earlier than those who sleep for between six and eight hours.

To put it more scientifically, there is a gradual increase in mortality risk for those who fall outside the six-to-eight-hour band.

Prof Franco Cappuccio, professor of cardiovascular medicine and epidemiology at the University of Warwick, has analysed 16 studies, in which overall more than a million people were asked about their sleeping habits and then followed up over time.

View article here: Sleep Duration and All-Cause Mortality: A Systematic Review and Meta-Analysis of Prospective Studies -

His analysis showed that 12% more of the short sleepers had died when they were followed up, compared to the medium sleepers.

However, 30% more of the long sleepers had died, compared to the medium sleepers. Cappuccio was aware of the possibility that people sleeping too long might be depressed, or might be using sleeping pills. He corrected for this, though, and found the association was still there.

His own theory is that people who sleep for more than eight hours sometimes have an underlying health problem that is not yet showing in other symptoms.

So, it's not the long sleep that is causing the increased mortality risk, it's the hidden illness.

View Press article on BBC/Health here