There is a gene that allows certain people to sleep under six hours and function normally. That part is true. But psychologist Nuria Roure, a sleep-disorder specialist, doesn't miss the chance to add: your odds of having that gene are very low. Most people who claim that six hours is enough have simply trained themselves to operate half-awake.

The standard is 7-8 hours for adults. The night runs through 4-5 cycles, with REM kicking in around 90 minutes after you fall asleep. To build up enough sleep pressure - the body needs to be awake for roughly 16 hours. Disturbing that rhythm is why a midnight workout or working until 2 a.m. wrecks the next day's sleep.

According to Roure, anxiety and a rushed lifestyle are behind 70 percent of poor-sleep cases. "Insomnia" gets diagnosed when the problem occurs at least three nights a week, when falling asleep takes more than 30 minutes, or when night-time waking is prolonged. This isn't "just a bad night" - it is a medical fact.

What the experts keep pointing at: most people don't know they sleep badly because they don't measure it. If you wake up tired, if coffee is mandatory to function before 10 a.m. - your body has already told you something. The question is whether you are listening.