If we talk according to Morden medical science normally an adult should sleep not less than 6 hours. That’s not against Islamic shariya too. But in Islam it has been condemned if a person sleeps too much. Also we should have at least 3 hours gap between our dinner and going to the bed. It has been highly recommended in Islam that we wake early in the morning and it has been advised against for a person to sleep while sun is rising. All these have been scientific approved too. So if we want to get up early we have to go to the bed early if possible. Sleeping plays very important role in our health. Like mid day nap has also many benefits even if it’s just for 15-20 minute after taking our lunch.
There are so many thing have described in this regards.