Getting 8 hours’ sleep a night is as healthful as eating 9 servings of fruit and vegetables and getting daily exercise—or so we’re told. In truth there’s no way to determine how much sleep any one of us really needs.
But the 8-hour recommendation is based on something, which is why we hear it so much. Recent studies show “a strong association between nightly sleep duration and mortality risk,” Michael Grandner and colleagues say in a paper on sleep duration and health. Overall, people who report sleeping 7-8 hours a night live longer than people who report sleeping 9-10 hours and those who report sleeping 6 hours or less.
The same is true of the relationship between sleep duration and cardiovascular disease (and related conditions such as hypertension and diabetes). Short and long sleepers tend to be more vulnerable to these ailments than people who sleep 7-8 hours a night. Of interest to those of us with insomnia, short sleepers (who sleep 6 hours a night or less) with poor quality sleep have a much higher risk of developing cardiovascular disease.
Counting the Hours
If you’re concerned you’re not sleeping enough, consider the possibility that you may be sleeping more than you think. About 5 percent of insomniacs have “paradoxical insomnia.” Usually pretty energetic during the day, they feel like they sleep just a few hours a night. Yet polysomnography (PSG)—the test performed in a sleep lab—shows 7 or 8 hours of sleep-like activity going on in most of the brain. (I’ll explain this phenomenon in another blog.)
Many of us perceive the lightest sleep stage as waking. Up to 50 percent of the time, the brainwave patterns of insomniacs who undergo sleep studies look exactly the same as those of normal sleepers. So our perception of sleep does not always jibe with sleep as measured by PSG. And the while PSG cannot assess sleep quality, its assessment of sleep duration is important. People whose polysomnograms show they get considerably less than 7-8 hours’ sleep a night are the ones most vulnerable to cardiovascular disease and early death.
Objective Sleep Measures
Here are 3 ways to find out how much you sleep.
- A sleep study. There are lots of downsides to going this route. It requires a doctor’s prescription, costs a lot, and is just a one-shot deal. Insomniacs’ sleep tends to vary a lot from night to night, and a sleep study is not going to provide information about your sleep duration over time, which is really what you want.
- Actigraphy. This involves wearing a wristwatch-type device to bed for several nights. The actigraph assesses your sleep-wake patterns based on bodily movement. It’s fairly reliable most of the time. It also requires a doctor’s prescription.
- Sleep-monitoring devices available without prescription. I’ve written about the Beddit, and a Google search will acquaint you with several others. These devices are relatively inexpensive, but none of them have been tested on insomniacs. They may not be sensitive enough to assess the nuances of insomniac sleep. (Coincidentally, just a few days after this blog post went out, Dr. Christopher Winter, who tested several sleep tracking devices on himself, posted a review of his findings in Huffington Post. It’s definitely worth reading if you’re considering buying one for yourself.)
Me personally? I know I’m a short sleeper but I’m not so concerned with racking up the hours. Health and longevity depend on several factors. Regarding sleep, I’m convinced that quality, and not quantity, matters more.
If you’ve undergone a sleep study or tried monitoring your sleep in some other way, what did you find out? Were you sleeping more—or less—than you thought?