The first myth is that we can get by on just four to five hours sleep a night—but we really do need those seven hours.
Another is that having an alcoholic drink just before we go to sleep will help us sleep better, say researchers at New York University's School of Medicine who reviewed more than 8,000 websites to identify the 20 most common assumptions about sleep.
One of the most persistent was that five hours sleep was enough, especially if it was supplemented with a short nap during the day, but there's isn't much science that supports the belief, the researchers say.
Another myth is that snoring is harmless. In and of itself it may be, says lead researcher Rebecca Robbins, but it could also be a symptom of sleep apnea, and this could be serious as it affects the way we breathe when we're asleep. Sufferers can stop breathing suddenly, and then start again, and this can cause the heart to stop beating.
Having a drink before sleep doesn't lead to a better sleep; in fact, alcohol interferes with the body's abilities to achieve deep sleep.
But the experts don't agree on everything. Some think that people who have a 'sleep debt' during the week—such as with shift workers—don't benefit by lying in over the weekend, but others don't agree and think it is beneficial.
So, when it comes to sleep myths, even the experts can't always agree.