A woman attending a talk I gave on insomnia was worried about developing Alzheimer’s disease because she wasn’t getting enough sleep.
“Sometimes I sleep only 4 hours a night,” she said, “and I’m really lucky when I get 5.”
After the talk I asked for details. Did she have trouble falling asleep? No. Did she wake up frequently at night? No again.
“When I fall asleep,” she said, “I’m out cold.”
What about her energy and alertness during the daytime? I asked. Did she feel tired, out of sorts, or foggy in the brain? No, no, and no. Then what was the problem?
“I read online that you’re supposed to get 7 or 8 hours of sleep,” she said, “but I can’t, no matter what. I read that people who don’t sleep enough get Alzheimer’s, and I don’t want to. I want more sleep.”
The Elusive 7 or 8 Hours
There’s a lot of talk these days about the health risks that accumulate if you sleep less than 7 or 8 hours a night.
- Cardiovascular Disease. Short sleep (sometimes defined as less than 6 hours of sleep a night, and other times defined as less than 5 hours of sleep a night) is linked to increased blood pressure and hypertension, and a greater risk of heart attack and stroke.
- Cancer. Short sleep duration makes you more vulnerable to breast cancer, colorectal cancer, and prostate cancer.
- Dementia and Alzheimer’s. A study of healthy older adults found that short sleep was associated with greater age-related brain atrophy and cognitive decline. Another study found that short sleep and poor sleep quality were associated more beta-amyloid in the brain (the main component of the amyloid plaques found in Alzheimer patients).
No wonder short sleepers are worried these days. Who wants a sentence of any of these illnesses hanging over their head?
Interpreting the Numbers
If you read reports of studies that appear in the popular media, it’s easy to misinterpret the results. Let’s say you learn that people with insomnia (who may be short sleepers and who also experience daytime impairments) are twice as likely to develop depression as people who sleep well (research has shown this to be true). “Twice as likely” might make it sound as though if you have insomnia, your risk for developing depression is pretty high.
But often missing from these reports is mention of the actual number of people who do develop depression at some time in their lives—information that could help you put the study results in perspective. Let’s say the lifetime risk of developing major depression in the US is about 17 percent (as shown in a study by Blazer et al in 1994). This figure, which would include both people with and without insomnia, indicates that most people—83 in 100—will never experience major depression in their lifetime.
Now let’s imagine (because I haven’t been able to lay my hands on actual figures) that among people who sleep well, the lifetime risk of developing major depression is 12 percent. If people with insomnia are “twice as likely” to develop depression, then 24 percent of insomnia sufferers will go on to develop major depression at some time in their lives, and 76 in 100 will not. In other words, your odds of dodging the bullet are 3 to 1 in your favor. “Twice as likely” does not sound so bad after all.
I don’t mean to downplay the significance of research exposing links between short sleep or insomnia and increased vulnerability to Alzheimer’s or any other illness. If sleeping less than 5 or 6 hours compromises health, we need to know it, and to understand why and how to minimize the risk.
I am suggesting that the results of these studies may not be as alarming as they seem at first glance. Beyond that, if they cause you to worry about your sleep, they do more harm than good. How long you sleep is determined in large part by genetic factors resistant to change. And—let’s face it—the last thing you need is one more worry to shorten your nights still further.
So what’s the secret to healthy aging if you clock 5 or 6 hours of sleep at best? You’ve heard it time and time again: get as much sleep as you can, eat healthful meals, and exercise daily.
If you’re a naturally short sleeper, what concerns do you have about your health?