Do you wake up each morning on your own without an alarm clock, feeling refreshed, alert and ready for the day ahead? Or do you drag yourself out of bed, grumbling to yourself until you get your first cup of coffee?
Most Americans, unfortunately, fall into the latter category. And the situation is getting worse. One study based on sleep records of full-time workers, found a significant increase in the number of persons getting less than six hours of sleep a night, during the period from 1975 to 2006. That’s true even though most Americans know that sleep plays an important role in good health and even longevity. Persons who average 6.5-7.5 hours of sleep a night live longer than those who sleep less, and even those who sleep more.
The effect of short sleep is easy to understand. Even over a one- to two-day period, subjects limited to four hours of sleep show increased heart rate and blood pressure, and markers of inflammation such as c-reactive protein (CRP) — all risk factors for heart disease. This kind of sleep deprivation is also associated with impaired glucose tolerance, leading to increased hunger/appetite, obesity and Type 2 diabetes.
Up to this point, studies have not found similar negative physical changes associated with long sleep duration, although observational studies indicate that long sleepers have an increased risk of illness, accidents, depression and death. Some researchers believe that many persons who habitually sleep 9 or 10 hours a night might have depression or a physical illness that accounts for their longer sleeping, and greater risk of early death.
How much sleep do we really need? For adults, experts agree that there is a great deal of individual variation. Some individuals go through most of their lives getting less than five hours sleep a night, while others seem to require 9 to 10 or more.
When you were in college and “pulled all-nighters” to study for exams, you probably assumed your mind and body would adjust — that you could catch up on lost sleep over the weekend. Studies over the last decade indicate that this was probably not the case.
In a study in 2003, researchers assigned subjects to groups sleeping four, six or eight hours for two week periods in the sleep laboratory. Every two hours during the day, the subjects were given a psychomotor vigilance test, measuring the kind of sustained attention and focus that are needed for tasks such as driving, careful reading of an exam question or working a math problem.
Over the study period, subjects getting eight hours of sleep had no lapses of attention or cognitive impairment, but those in both of the other groups showed steady declines with each passing day. By the end of two weeks, those sleeping six hours a night had cognitive impairments similar to subjects in another study deprived of sleep for 24 hours straight.
At first, the sleep-deprived subjects realized that they were not at their best, but as time went on, they insisted that sleepiness was no longer affecting their performance — even though it clearly was.
How about increasing sleep time? One study asked students to “sleep as much as possible” over several weeks. During the first week, the subjects’ average sleep time increased from 7.5 to 9-9.9 hours a night, and these increased sleep times were associated with better alertness and less daytime sleepiness.
However, over the next several weeks, the students’ sleep time gradually came back down to an average of about 8.5 hours a night. The researchers theorized that the subjects probably made up for previous sleep deprivation, then reached their maximum sleep level during the following weeks.
Researchers continue to study the interaction between (1) basal sleep need and (2) sleep debt. The first refers to the sleep needed on a regular basis — seven to eight hours for most persons. Sleep debt occurs when you fail to meet that basal need because of sickness, stress, poor sleep habits or simply a busy schedule.
Sleep debt can be paid off, although one or two nights of sleeping in over the weekend usually is not enough to get us back to optimal alertness.
When pressed by a busy schedule, it’s tempting to sacrifice an hour or two of sleep — sometimes on a regular basis — in order to get things done. Unless you’re doing something that requires little thought, that may not be a smart idea. As one researcher put it, you may be “trading time awake at the expense of performance.”
Rupp is a certified information and referral specialist on aging for NODA Area Agency on Aging. Contact her at 237-2236.