How much sleep is enough?

Sleep is a time for the body to replenish its expended energies, to repair itself or to recover from the wear-and-tear of daily living. As such, it is a very important human need that has to be properly satisfied. But how much amount of sleep is necessary?

A person's sleep requirement goes inversely with his age. As a general rule, young people need more sleep hours than grown-ups. A young body needs to sleep more in order to allow its full development. But only very few people take their sleep issue seriously. Many think it is okay to just sleep for a few hours or to take a quick nap just when they feel sleepy. This is not quite right, according to recent sleep research.

Economic hurdles compel people to work more and at odd hours that their sleep time has been cut by about 20 percent over these last decades. And still there's family and other social activities that need time and attention, so that the minutes or hours taken off from people's sleep are very seldom, if at all, paid back.

Chronic lack of sleep can lead to ill health and erratic, even potentially dangerous, behavior. A woman who hadn't had sleep for nights in a row switched her electric flatiron on when she wanted to watch TV. Another one loaded her dirty dishes into the clothes dryer, instead of putting them in the sink. A staff of a Manila bank worked overtime for several nights in order to earn extra to buy a ticket for the recent Pacquiao-Larios boxing match. He got a prime ticket, but was so sleepy that he dozed off in his seat in the early minutes of the fight and remained asleep until it was all over.

The more common scenario is of sleepy people making mathematics errors, breaking things and being irritable. Other, more immediate effects of sleep deprivation on health and wellbeing include impaired cognitive skills and poor physical performance. Sleepy people have low comprehension levels and lack the stamina to do even ordinary tasks.

There is a rising incidence of accidents caused by drivers falling asleep at the wheel. Laboratory experiments have established that lack of sleep can cause people to slip into "micro-sleeps". These are very short lapses in consciousness, so brief, in fact, that the person experiencing them may not be aware of it when it happens. Micro-sleeps last for a quick two seconds, on average, and can occur even with the eyes wide open.

Our internal biological clock regulates the time we are each to spend on sleep. This explains why we often feel uneasy when we linger in bed way too long. We feel the same - but often worse - when we lack sleep. And the brain is very accurate in keeping account of the amount sleep lacking. If a person gets an hour less than a full night's sleep, for example, that sleep deficit is carried into the next day. Hence, he is more likely to feel sleepy, or actually fall asleep, during the day. If it happens at the workplace, the consequences can be bad.

Sleep deprivation accumulates continually until the owed time is satisfactorily offset or compensated. In a six-day work week, if a person got only six hours of sleep each night instead of the required eight hours, he would owe himself a total of twelve hours of sleep that week. Around the fifth or the sixth day, he may begin to feel so sleepy, as if he'd stayed up all night.

Many offices are close or have a skeletal workforce on Saturday afternoons. Workers like to go on a half-day off to rest. Yet even if they spend the whole afternoon sleeping, those few hours are still short of the total time of sleep they may have lacked during the week. And since Sunday is family or social day, it cannot be relied upon to further offset that accumulated sleep deficit. By Monday, habitual sleep debtors, returning either to work or school, are usually feeling as worn out as they were during the weekend.

It is not clear how long the brain keeps a record of uncompensated sleep debt. Research has only been able to measure short periods, ranging from weeks to a month. It is thought that periods of sickness, including those triggered by lack of sleep, help to offset accumulated sleep debt. Those ailments that need confining the patient to bed are specifically helpful in this respect.

People are ordinarily bad judges of their own sleep needs. But sheer common sense can help. It only takes for one to observe his alertness level during the day in relation to the length of his sleep the night before. If he feels sleepy at certain times, then he needs to add to his nightly sleep, in certain time fractions of, say, 30 minutes or 1 hour, until the daytime sleepiness diminishes or is gone completely. By the time he feels sleepy only around his regular bedtime, he is most probably meeting his personal sleep requirement adequately.

The pioneering medical principle still stands-that although sleep needs vary among people, those that sleep about eight hours daily, on average, tend to live healthier and longer.