German scientists say they have discovered a gene that may explain why some people can get by with less sleep than others.

Researchers called chronobiologists, from Ludwig Maximilians University in Munich, say that a gene called ABCC9 appears to affect the length of time we need to sleep. The same gene has previously been linked to heart disease and diabetes.

The Europe-wide study saw 4,000 people from seven EU countries fill out a questionnaire assessing their sleep habits. The researchers then scanned the genomes of the volunteers and looked for variations in their genes that correlated with their answers about their sleep patterns.

They discovered that people who had two copies of one common variant of ABCC9 slept for significantly shorter periods than people with two copies of another version.

The finding, described in the journal Molecular Psychiatry, could explain why light sleepers are able to get by on just a few hours of shut-eye a night, says Toronto-based sleep expert Dr. Colin Shapiro.

"This tells us that we are programmed in some way to need a certain amount of sleep, just as some people are programmed to be taller and others are programmed to be shorter," he told CTV's Canada AM Tuesday morning.

But Shapiro, who was not involved in the European study, says just because some people think they are programmed to get by on just four hours of sleep, that's not an adequate amount of sleep for anyone.

"A lot of people think they might be coping, but in reality, they are not likely to be thinking rationally, they are not likely to be making the best decisions they could," he said.

If you want to determine how much sleep your genes say you really need, Shapiro suggests taking a week or two to allow yourself to have as much sleep as you like and see what comes naturally.

"If you find that you're sleeping a couple of hours longer than you normally do every day, you might think that you're coping with your day-to-day life, but you're probably functioning below par because of your relative sleep deprivation," Shapiro said.

He also notes that it's not just our mental function that suffers when we are sleep-deprived; there is evidence inadequate sleep takes a toll on our body as well.

"There's all sort of evidence that there's an increasing tide of obesity because of sleep deprivation," he says, adding there are also studies that suggest that people who don't get enough sleep simply don't live as long.

"Sleep loss seems to be a trigger in things as diverse as diabetes to cardiac disease," Shapiro says.