Research from a RAND report shows people who sleep fewer than six hours a night are 2.4 percent less productive than those who get between seven and nine hours.

Overall, the UK loses hundreds of thousands of working days due to insufficient sleep, costing the economy £40bn each year, or almost 2 percent of gross domestic product.

These numbers might contradict countless stories about the very successful businesspeople, chief executives, and heads of state who have claimed to get by on little or no sleep.

In reality, the science shows that just 1 percent of the global population are naturally short sleepers. These people really do only need six hours sleep or less a night to feel genuinely refreshed.

There are two main causes of productivity losses at work. The first is absenteeism, when people simply don't show up to work. This could be due to illness, as insufficient sleep increases the risk of infectious diseases like colds or flu. The second is presenteeism — when people do show up, but do not work to their full potential. They might be nursing a mild illness, a headache or finding it hard to concentrate because they are overtired.

Read the full article on sleep and productivity by Marco Hafner at RAND