Can't sleep? - you're probably not rich enough!

According to a study by American researchers not only are we not getting as much sleep as we thought, when it comes to sleeping there are big differences among races and genders.

In a recent study of 669 people a research team at the University of Chicago has found that wealthy white women get a better night's sleep, on average, than other groups.

A study of 38- to 50-year-olds found white women sleep the longest, an average of six hours and 42 minutes every night, but still less than the seven hours they claimed to have slept.

They also go to sleep the fastest, spend the most time in bed and sleep most efficiently.

It was also found that African-American men slept the least, and had on average five hours and six minutes a night.

They also took the longest to fall asleep, spent the least time in bed, and slept the least efficiently.

The study participants were asked to keep sleep logs and record when they got into bed and when they woke up.

They also wore devices to record when sleep actually began and ended.

It appears that the more money a person earns, the better they tend to sleep, with those earning over 100,000 dollars a year falling asleep quicker than those making 16,000 dollars a year.

The poorer people in the study also got 15 minutes less sleep.

The study is published in the American Journal of Epidemiology.