Still remember the last time when you cannot keep your eyes open no matter how hard you try? Congratulations to the ones who don't! You are one of those lucky people who have an adequate amount of sleep every day and don't feel tired oftentimes. However, if you happen to fall asleep on a regular basis, it may be a bad sign showing that you are heavily indebted...in sleep!

Most adults today get about an hour less sleep than the average sleep time half a century ago. It goes without doubt that sleepiness affects our daily productivity and mood. However, since the mental and physical consequences of sleep debt are largely unknown to the public, sleep is commonly neglected.

Sleep deprivation is an additive process. Each of us has a certain sleep requirement, which varies for every person and can be averaged to around eight hours per night. When we fall short of the minimal sleep requirement, we incur a sleep debt that prevents us from functioning at our optimal level. This deficit can add up over time whenever you compromise your sleep need. In other words, sleep debt is accumulative and, if not addressed, it can affect your mood and performance in several weeks' time and beyond!

So, what happens when you have a high sleep debt? It starts taking over your mind and your life. Studies have shown that people with large sleep debts suffer from mood shifts, depression, irritability, stress, impaired memory, weight gain, reduced immunity and lack of interest in socializing with others. For students, you may fall asleep in lectures and have missed important points that are going to appear on the finals; for employees, you may be too tired to complete the report your boss needs, and fail to turn it in by the deadline. These consequences may still sound insignificant to you, but excessive sleep debt can actually be so harmful that it threatens lives!

According to a study conducted by the National Highway Traffic Safety Administration (of America), it is conservatively estimated that 100,000 police-reported crashes happen each year as the direct result of driver fatigue, resulting in an estimated 1,550 deaths, 71,000 injuries and $12.5 billion in monetary losses. The actual figures may be considerably higher since it is difficult to attribute crashes to sleepiness. To quote William C. Dement, the founder of the Stanford University Sleep Clinic, “drowsiness is red alert!” Drowsiness is found to be gradually outstripping alcohol as a cause of accidents in transportation, particularly on the highway.

Intimidated by the drastic consequences? Want to know how sleep-deprived you are? A simple way to measure the level of sleep debt would be a home-adapted version of the Multiple Sleep Latency Test (MSLT). During daytime, you may lie down in a comfortable environment (e.g. your own bed) with loose clothing and see how fast you can fall asleep. A result of 15-20 minutes corresponds to the “Good Alertness” level, which means that you probably have negligible sleep debt. Taking less than 10 minutes on the MSLT implies a strong sleep tendency and strong sleep drive, and a result of less than 5 minutes indicates severe sleep deprivation, or the “Twilight Zone” as Dr. Dement calls it. Dire consequences can be expected, and you may fall asleep inappropriately while on the job, studying, driving long distances, or in any other circumstance.

To eliminate the sleep debt, the answer is simply to get more sleep. A small sleep debt, say a week of sleeping 6 hours a day, can be easily eliminated by a few weeks of extra sleep. However, for a large sleep debt, it would take more time to alter its effect. Don't expect that sleeping through an entire weekend is enough to compensate for a huge sleep debt, since the body's biological clock will tend to keep you awake at certain times during the day (commonly in the afternoon). In a study by Dr. Thomas Wehr and his colleagues at the National Institute of Mental Health, most subjects were found to have a sizeable sleep debt of one to two dozens hours. Once the sleep debt was repaid, they averaged a daily sleep time of 8 hours and 15 minutes and experienced a markedly increase sense of well-being, mood and energy levels.

Therefore, it is necessary to ensure that once the sleep debt has been repaid, a healthy sleep habit is adopted and maintained. The simplest way to protect yourself is to keep your sleep debt low in the first place by getting adequate sleep. Even if you lose sleep because of a particularly demanding schedule or an emergency, try getting extra sleep in advance of the crisis, or taking naps afterwards. It is surprising that we spend one-third of our lives sleeping, yet we know so little about it and tend to overlook its importance. Once again quoting Dr. Dement, “Managing sleep is exactly analogous to managing money.” Just as you don't want to go bankrupt, why would you want to be sleep indebted? Further information about sleep debt or sleep in general can be found on http://www.end-your-deprivation.com/