WellnessOptions Magazine issue09 - Life energy & fatigue

By Manny W. Radomski & Stanley Coren

Are we mortgaging our health with sleep debt?
Sleepiness and fatigue are endemic. Many of us are tired every day because we build up a large sleep deficit.

In the last 20 years, we have experienced a significant decrease in leisure time, a rise in annual work hours, and a reduction in average time asleep by 20%. About 27% of s have only 6 to 6.9 hours of sleep per night. Our brains keep an account of how much sleep is owed. If we deprive ourselves of 1-2 hours of sleep per night, this loss accumulates such that at the end of a week, we will have accumulated a sleep debt of 5-10 hours. This “sleep debt” must be repaid.

Are we at risk?
Research has shown that sleeping 6 or fewer hours per night increases the risk of the age-adjusted death rate by 1.7 times compared to sleeping 7 or 8 hours per night.

Lack of sleep makes us clumsy and less able to think quickly and clearly. It reduces our creativity and short-term memory. By some accounts, each hour of lost sleep translates into a temporary loss of one IQ point. In jobs that demand full attention, such as driving and working with hazardous machinery, loss of sleep can be fatal.

A study by the U.S. National Commission on Sleep Disorders has determined that the direct cost of accidents resulting from sleep debt are $56 billion a year. As well, in a single year there are approximately 25,000 deaths and 250,000 disabling injuries from these accidents.

People with large sleep debts often experience “microsleeps,” which are brief 10 - 60 seconds in which the brain enters a sleep state, causing a momentary blackout. Driving at 48 kph, a microsleep of 10 seconds means traveling more than the length of a football field before awakening.

How is performance impacted?
US sleep researchers have studied the effects of sleeping on performance after different lengths (7.5, 5, 3, 2, 1, 0 hours) of sleep. Results show that performance of calculations is impaired with less than 3 hours of sleep, while, fatigue, mood disturbances, were reported with less than 5 hours of sleep.

Another study shows that restricting sleep to 4 hours per night for 2 weeks results in linear decrements for most performance measures. The ability to perform after 14 days on 4 hours per night is equivalent to having been awake for 48 hours.

Is sleeping more always better?
The daily amount of sleep we should have is the amount that allows us to remain fully awake and able to sustain normal levels of performance. The amount of sleep we need is as individual as the amount of food we need.

However, an average 7-8 hours of sleep daily is enough for most people. Most sleep researchers agree that extension of sleep beyond 7-8 hours by 2 or more hours produces only marginal benefits for performance.

Can oversleeping lead to fatigue?
It is impossible for a normal person to oversleep. We simply wake up when we have enough sleep. What is referred to as “overslept” occurs when we are sleep deprived, then slept for sometime, but not enough to pay back all sleep debt. The resulting fatigue is the body’s signal that more sleep is needed.

When we switch annually to daylight saving time in the spring, traf¥c accidents increase by 7 % the day after (losing an hour of sleep). In the fall, when we gain an hour of sleep, there is a reduction in traf¥c accidents by approximately 7 %.

References:
Mitler M et al. Catastrophes, sleep, and public policy: consensus report. Sleep 1988; 11: 100-09.
Schor JB. The Overworked American: the unexpected decline of leisure. NY: Basic Books1991.
DementWC, Vaughan C. The Promise of Sleep. Dell Publishing, NY. 2000.
Coren S. Sleep Thieves. Free Press Paperbacks, NY, 1997.
Dinges DF et al. Cumulative sleepiness, mood disturbance and psychomotor vigilance performance decrements during a week of sleep restricted to 4-5 hours per night. Sleep 1997; 20: 267-277.