Boredom unmasks sleep debt. If you get sleepy when bored, or while trying to read or listen to a lecture, you have probably been deprived of enough sleep. Normal biological rhythms induce sleepiness between 1 p.m. and 4 p.m. and between 2 a.m. and 6 a.m.
A recent British study suggested that over the five year period between 1992 and 1997, the average person has lost 12 minutes sleep a night; it is estimated that two-thirds of Europeans now sleep less than seven hour a night (most experts recommend at least 7.5 hours).
Only 5% of the Americans experiencing sleep-related problems consult a doctor about them, although admitting that their daytime sleepiness interfered with their daytime activities.
It is reported that sleepiness is second only to drunkenness as a cause of traffic accidents. In the USA in 1998 100,000 road accidents a year were sleep-related, including 1,500 vehicular deaths and 71,000 injuries. More than 20% of drivers report having fallen asleep more than once while driving. In Canada, traffic accidents increased by 7 percent on the day after summer time was introduced (one hour lost sleep) and decreased by 7 percent on the day after winter time was introduced (one hour more sleep).
The most sleep-deprived group may be high school and college students. From the ages of 17 to 25, sleep needs are greater than at any other time of life after early childhood, but the pressures to postpone or even skip sleep are also greatly increased. The average student sleeps only six hours, but needs about 10 hours, accumulating a sleep debt of 4 hours a night. The average American now probably accumulates a sleep debt of 500 hours a year.
Young children who miss naps and lack sleep may be more prone to accidental injury. Sleeping less than 10 hours a day (including naps) put children at an 86% higher risk of injuries caused by accidents such as slipping, tripping or falling. Especially vulnerable are children aged 3 to 5. The injury risk for boys increased by up to four times if they have been awake for at least 8 hours straight. Research based on hospital admissions shows that only a small difference in sleep - about 20 minutes a day - may distinguish a well-rested period two days before an injury and a "sleep-deprived" period just prior to visiting the emergency department.