Meanwhile, 12 percent of Americans say they SLEEP less than six hours without consequences, Williams said. As a physician, he is aware that inadequate sleep has been linked to a growing list of cardiovascular, metabolic, mood, immune system and cognitive problems - or, as one researcher put it, just about everything bad. People with sleep apnoea, who sometimes sleep long hours, may be in an entirely different category because of poor sleep quality. Those few extra hours away from his pillow, he believes, have allowed him to write books, run marathons and achieve his lofty career goals.
Sleeping fewer hours will eventually lead to having to make up for it with more sleep on subsequent nights. In a global sample of more than 10,000 people, researchers concluded that, in terms of brain function, sleeping less than 4 hours was the same as adding 8 years to your age. Everyone knows someone's uncle's friend who says they sleep two hours a night and they're totally fine, says Robbins. Several sleep researchers said they are most concerned about short sleepers, those who sleep less than four hours, regardless of how this habit makes them feel.
Evidence shows that adults need between seven and eight hours of sleep each night, and regularly sleeping less than five hours a night is linked to cardiovascular problems and poor immune health. Experts also suspect that feeling tired or groggy after four to six hours of sleep is a sign that something is wrong.