You Don't Need 8 Hours

I hear from a reliable source (specifically Daniel Kripke, the co-director of research at the Scripps Sleep Center in La Jolla, California) that WE DO NOT NEED 8 HOURS OF SLEEP. *gasp* Haven't people been telling us for years that 8 is the magic number of hours we need to sleep each night? Apparently, it is no longer.

According to Kripke, "people who sleep between 6.5 hours and 7.5 hours a night, as they report, live the longest. And people who sleep 8 hours or more, or less than 6.5 hours, they don't live quite as long." Kripke essentially says here that sleeping too long is just as bad, or even worse, than sleeping too little. However, even though people who sleep 6.5-7.5 hours seem to live longer, Kripke admits that "we don't know the reasons."

A check with the National Sleep Foundation, which recommends 8.5-9.25 hours of sleep for teens aged 11-17, and 7-9 hours for adults, leaves me wondering whether Kripke knows what he's talking about or the National Sleep Foundation website is outdated. Who is right?

As it turns out, that quick glance at the chart is a bit misleading. In the actual article preceding the chart, the Sleep Foundation also says "healthy adults have a basal sleep need of seven to eight hours of every night." The key word here is basal. Apparently researchers define basal sleep need as "the amount of sleep our bodies need on a regular basis for optimal performance," and sleep debt as "the accumulated sleep that is lost to poor sleep habits, sickness, awakenings," etc. So even if someone sleeps the correct amount of time for their basal sleep need, one still needs to make up for sleep he or she has lost on other nights. Not to mention, basal sleep need differs among individuals, so there is no "magic number" of sleep that applies to everyone.

In addition, there are also circadian dips to deal with, different times when people are programmed to feel more sleepy. My circadian dip usually comes during 2nd block at school (9 am - 10:30 am) no matter what class I have. This turns out to be quite inconvenient, especially because most standardized tests, like the SAT and Advanced Placement exams, are given in the morning.

Ironically, this article, too, refers to the research by Danial Kripke, and his fellow researcher Shawn Youngstedt. After analyzing American Cancer Society surveys of 1 million adults, they found that people who got 7 hours of sleep had a lower mortality rate. So, does this mean that sleeping 7 hours is healthier? Or does it just mean fewer people who slept 7 hours died? Researchers argue that sleeping too little and sleeping too much is associated with "increased morbidity (illness, accidents) and mortality (death)." However, is this a cause-and-effect relationship, or merely a correlation?

According to Kristen L. Knutson, PhD, Deparment of Health Studies, University of Chicago, "There is laboratory evidence that short sleep durations of 4-5 hours have negative physiological and neurobehavioral consequences." So short amounts of sleep may be dangerous. But why?

It seems the further I research the more questions I have. As I research, maybe I'll perform my own self-study. It won't be very reliable, but it'll help me get better in touch with what I'm dealing with. Tonight I will sleep for 7 hours. And tomorrow night. We'll see how it turns out!