Some people need more sleep than others, and a new study has found that our personal sleep requirements may be down to our genes, reports Medical News Today.

Some people can function perfectly well on just a few hours of sleep, while others need a good 10 hours or more each day to remain chipper. Famously, Donald Trump claims that he only needs 3–4 hours in bed each night.

This isn’t news, of course; these differences are well-documented. However, until recently, very little was known about why such variation exists.

A recent study set out to understand why some individuals appear to be able to burn the candle at both ends while others need to spend half of their lives under the sheets.