How Many ZZZs Do You Really Need?

What's the purrrrfect amount of sleep?
Image: Shutterstock

How many hours of sleep do you get each night? How much would you get if you didn’t have to set your alarm clock each morning? As a society, we’ve come to believe the ideal amount of sleep per night is 8 hours for adults. I’ll be the first to say that if I sleep without interruption, I tend to go for nine hours, meaning my sleep cycles are likely each 3 hours long or 4.5 hours long.

“Everyone is different,” is the phrase I generally go to when talking about how much sleep people “need” to get on average each night. But there’s some interesting new research being done that is suggesting the “eight hours” rule might not actually be the ideal amount of sleep.

In general, Americans these days are getting fewer hours of shuteye than in the past, and several studies over the past few decades have suggested that seven hours is the optimal amount of sleep for cognitive and physical health.

For example, the University of California San Diego conducted a six-year-long study involving over a million people and concluded that the optimal amount of sleep per night is between 6.5 and 7.4 hours. The researchers say that those who tended to sleep between those amounts had a lower mortality rate than those who got either more or less sleep on average. The study controlled for 32 different health factors and was published in 2002.

Of course, many experts have pointed out potential flaws in the research, such as whether it factored in illnesses, human error in self-monitoring for sleep times, and genetic differences and predispositions. One study found that skipping out on even a little extra sleep (20 minutes) could impair memory and overall performance. Too much sleep, however, has been associated with a wide variety of health problems—like obesity, diabetes, cardiovascular disease, and higher mortality rates.

“The problem with these studies is that they give you good information about association but not causation,” says Timothy Morgenthaler, who is president of the American Academy of Sleep Medicine. He recommends seven to eight hours of sleep per night, with an evaluation of how you feel individually—because optimal sleep times can vary largely.

One thing is for sure: there’s certainly more research to be done. The Center for Disease Control (CDC) has agreed to fund a panel to review and report on all existing sleep research. The panel will be made up of researchers and medical specialists, who are to deliver new recommendations on sleep by 2015.

What do you think about this new research? Are you a tried-and-true 8-hours believer, or do you have a different optimal sleep time?