Conventional wisdom holds that adults need about 8 hours of sleep per day. For basic functioning, maybe.
But it’s more like 10 hours per day if you’re athletic, busy, and actively engaged in a productive life. For optimal functioning, you need 10 hours of rest spread over the night and day.
It’s very simple: if you feel drowsy any time during the day, you’ve already incurred a sleep debt.
When you consistently get less sleep than you need, your mental and physical performance suffers.
How to measure your sleep debt:
If you go to bed in a comfortable, darkened room and fall asleep within 5 minutes, you probably have a serious sleep debt.
If it takes 15 – 20 minutes to fall asleep, you’re probably well rested.
Small sleep debts (10 – 20 hours in a healthy adult) are not a problem. In fact, they’re normal.
Large debts are dangerous—and generally ignored by both society and doctors. Sleep expert Dr. William Dement claims that 50 hours is about the maximum debt anyone can stand.In corporate life too many busy executives carry a large debt. But nobody transcends their physiological needs.
Of the people claiming to get by on a few hours of sleep, independent investigation found all such claims to be false, greatly exaggerated, or delusional.
You can fool yourself when espousing such nonsense but you can’t fool your own body. So pay your debt.
How to Sleep Well
Comedian Stephen Wright was asked “did you sleep well?’
“No,” he replied, “I made a few mistakes.”
It takes only 3 things to sleep well:
Make sure your bedroom is
- cool (temperature around 65 degrees F / 18 degrees C)
The Costs of Sleep Debt
Here’s what happens if you refuse to pay off your sleep debt.
- You become stupid. Your decision-making ability declines precipitously when you’re sleep deprived. You make bad decisions, costly errors, poor choices, all of which have consequences.
- Failing to get enough sleep night after night can compromise your health and may shorten your life.
- Inadequate sleep can profoundly diminish memory, learning, creativity, productivity, emotional stability, and physical health.
- Poor sleep is a risk factor for depression and substance abuse. and pay attention.
- Insufficient sleep can lead to weight gain. The hormone leptin, which tells the brain that enough food has been consumed, are lower in sleep-deprived people while levels of ghrelin, which stimulates appetite, are higher.
- Numerous bodily systems are affected negatively by inadequate sleep: the heart, lungs and kidneys; appetite, metabolism and weight control; immune function and disease resistance; sensitivity to pain; reaction time; mood; and brain function, according to sleep specialists at the University of Pittsburgh School of Medicine and Western Psychiatric Institute and Clinic.
- Put it this way, “Sleep affects almost every tissue in our bodies,” said Dr. Michael J. Twery, a sleep specialist at the National Institutes of Health.
Need more reasons to rest?
What science says:
- The body’s ability to process glucose is also adversely affected, which may ultimately result in Type 2 diabetes.
- The risks of cardiovascular diseases and stroke are higher in people who sleep less than 6 hours a night. Even a single night of inadequate sleep can cause daylong elevations in blood pressure in people with hypertension.
- Inadequate sleep is also associated with calcification of coronary arteries and raised levels of inflammatory factors linked to heart disease.
- The risk of cancer may also be elevated in people who fail to get enough sleep. A Japanese study of nearly 24,000 women ages 40 to 79 found that those who slept less than 6 hours a night were more likely to develop breast cancer than women who slept longer.
- The increased risk may result from diminished secretion of the sleep hormone melatonin. Among participants in the Nurses Health Study, Eva S. Schernhammer of Harvard Medical School found a link between low melatonin levels and an increased risk of breast cancer.
- A study of 1,240 people by researchers at Case Western Reserve University in Cleveland found an increased risk of potentially cancerous colorectal polyps in those who slept fewer than six hours nightly.
- During sleep, the body produces cytokines, cellular hormones that help fight infections. Thus short sleepers may be more susceptible to everyday infections like colds and flu. In a study of 153 healthy men and women, Sheldon Cohen and colleagues at Carnegie Mellon University found that those who slept less than seven hours a night were three times as likely to develop cold symptoms when exposed to a cold-causing virus than were people who slept 8 or more hours.
- Some of the most insidious effects of too little sleep involve mental processes like learning, memory, judgment and problem-solving. During sleep, new learning and memory pathways become encoded in the brain. Adequate sleep is necessary for those pathways to work optimally. People who are well rested are better able to learn a task and more likely to remember what they learned. The cognitive decline that so often accompanies aging may result partly from chronically poor sleep.
- With insufficient sleep, thinking slows; it’s harder to focus and pay attention, so you make poor decisions and take undue risks. These effects can be disastrous when driving a car or driving a business.
- In driving tests, sleep-deprived people perform as if drunk and no amount of caffeine or cold air can negate this effect.
Sleep Debt: Bad Things Happen
- Some years ago in an anonymous survey, 42% of the house staff of a San Francisco hospital, admitted to killing at least one patient by making a fatigue-related mistake.
- According to recent estimates a third of all vehicular accidents are caused by sleep deprivation.
- In a recent study 82% of truck drivers said they pull over only when their heads drop or when they experience visual hallucinations—in other words, after they’ve already fallen asleep. 70% of these drivers turned out to have sleep apnea, a serious disorder, 13% of the cases severe.
- Many airline accidents have been caused by pilot fatigue: one study within an airline cockpit showed that pilots and co-pilots were falling into short “microsleeps” even while landing the airplane (lab observations show that drooping eyelids usually indicate microsleep, whereas if your eyes close you’re actually sleeping for awhile—usually without knowing it).
- Chernobyl, Exxon Valdez, Challenger were all caused by fatigue. In the press, the Exxon Valdez oil spill was attributed to the captain’s drinking problem but the official report concluded that the real cause was poor judgment by the pilot—who had had only 4 hours sleep in the 48 hours before the accident. The Challenger explosion was due to sleep deprived NASA personnel.