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By Melissa Tennen, HealthAtoZ writer
Maybe you missed a few hours of sleep last night. Come to think of it, you didn't get to bed on time Monday night either. You feel okay. What's the harm?
Plenty. Missing some sleep could be as bad as getting no sleep, says a new study from the University of Pennsylvania appearing in the journal Sleep. Researchers found that many people who are living on less than the standard eight hours may not be aware how tired they are or how the shortfall is affecting their brains.
"The assumption is that your body will adapt and live with less sleep," says Hans P. A. Van Dongen, Ph.D., assistant professor of sleep chronobiology at the Psychiatric School of Medicine at the University of Pennsylvania and lead investigator of the study funded by the National Institute of Nursing Research of the National Institutes of Health.
However, that is not the case.
Researchers found people in the study who slept four to six hours a night for 14 consecutive nights reacted more slowly than they would have on eight hours. This performance was equivalent to people who did not sleep at all for two nights. Yet these people said they did not feel tired.
And that is where trouble begins.
"People who need to perform certain functions in their jobs may reduce their speed to maintain accuracy," Van Dongen says. "A worker on an assembly line may take a little extra time. If you are writing, you might do extra proofreading. It's such an automatic process that the brain does. Most of the time, we are not even aware of this. The brain just naturally does this."
Usually, this isn't much of a problem, Van Dongen says, the few extra minutes here and there. But you could be in big trouble when you have to think fast.
"In a car, you see lights, things coming at you, cars turning. In a car, the brain cannot do these tricks anymore," he says.
It's not just driving, points out Joyce Walsleben, Ph.D., R.N., research associate professor of medicine at New York University's School of Medicine and diplomate of the American Academy of Sleep Medicine.
"It's the people in critical roles like the military, like health care workers who work night shifts. It's anything that is very critical and requires quick judgments where you are going to see a problem. It's the things that require more from you but you have less to give," she says, lauding the study as important in the field of sleep research.
"The sense of feeling good is not a good measure," she says.
Adults need 8.16 hours during a 24-hour cycle, according to this research, although the study also showed that this number can vary from one person to another.
The study looked at 48 healthy adults ages 21 to 38. This is a group commonly associated with sleep deprivation because of demands such as raising children and working long hours. The researchers say more work needs to be done looking at other age groups.
Van Dongen says we may have turned off our sense of sleepiness because of our daily routines and the ways we work to help stifle the sense of tiredness that the body is sending to the brain. Caffeine, the long commutes, the frantic activities of shuttling the kids to the doctor - all things cloud your ability to tell just how tired you are.
It's a catch-22, Van Dongen says. By stealing time from sleep to have enough time during the day, we are actually losing time because of the impaired brain functioning.
"People should be aware that sleep is not a waste of time and realize sleep is actually valuable," he says.
Lack of sleep doesn't only affect your ability to perform throughout the day. It could also lead to physical problems, such as:
- Obesity: Sleep plays a role in the body's ability to secrete neurohormones. As the amount of hormone secretion decreases, the chance for weight gain increases.
- Blood pressure: Your blood pressure naturally goes down during your sleep. But lack of sleep interrupts this cycle, potentially leading to hypertension and cardiovascular problems.
- Diabetes: The body's ability to use insulin could be impaired, possibly leading to diabetes.
As many as 47 million adults may not be getting the minimum amount of sleep they need at night, according to a National Sleep Foundation (NSF) 2002 poll. People reported 6.9 hours weeknights and 7.5 hours during weekends. At least 30 percent of people surveyed got less than seven hours on weeknights and two-thirds get less than eight hours of sleep on a weekend night.
At least 58 percent of American adults had at least one symptom of insomnia in 2002, according to NSF. Insomnia includes waking too early, having trouble falling asleep and waking throughout the night. Chronic insomnia could indicate a disorder such as sleep apnea or mental illness such as depression.
Most people, even the elderly, need between seven to eight hours, NSF says. There is no evidence that the body's need for sleep diminishes with age.
This article was reviewed and updated June 2007.
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