How Much Sleep Do We Need?
The amount of sleep each person needs depends on many factors, including age. Infants generally require about 16 hours a day, while teenagers need about nine hours on average. For most adults, seven to eight hours a night appears to be the best amount of sleep, although some people may need as few as five hours or as many as 10 hours of sleep each day.
The amount of sleep a person needs also increases if he or she has recently been sleeping less. Getting too little sleep creates a "sleep debt," which is much like being overdrawn at a bank. Eventually, your body will demand that the debt be repaid. We don’t seem to adapt to getting less sleep than we need; while we may get used to a sleep-depriving schedule, our judgment, reaction time and other functions suffer.
People tend to sleep more lightly and for shorter time spans as they get older, many individuals notice that they do not need about the same amount of sleep as they did in early adulthood. About half of all people over 65 have frequent sleeping problems like insomnia, and deep sleep stages in many elderly people often become very short or stop completely. This change may be a normal part of aging, or may result from health problems and their treatments that are common in elderly people. People with more numerous health problems tend to have more sleep problems.
For normal, healthy individuals, if you feel drowsy during the day, even during boring activities, you probably haven’t had enough sleep. If you routinely fall asleep within five minutes of lying down, you probably have severe sleep deprivation, possibly even a sleep disorder. Microsleep, or very brief episodes of sleep in an otherwise awake person, is another mark of sleep deprivation. In many cases, people are not aware that they are experiencing microsleeps. The widespread practice of "burning the candle at both ends" has created so much sleep deprivation that abnormal sleepiness is now almost the norm.
Sleep deprivation is dangerous. Sleep-deprived people using a driving simulator or performing a hand-eye coordination task perform the same or worse than those who are legally intoxicated. Sleep deprivation also magnifies alcohol’s effects on the body, so a tired person who drinks will become much more impaired than someone who is well rested. Driver fatigue is responsible for an estimated 100,000 motor vehicle accidents and 1,500 deaths each year, according to the National Highway Traffic Safety Administration. Since drowsiness is the brain’s last step before falling asleep, driving while drowsy can – and often does – lead to disaster. Caffeine and other stimulants cannot overcome severe sleep deprivation. The National Sleep Foundation says that if you have trouble keeping your eyes focused, can’t stop yawning, or can’t remember driving the last few miles, you are probably too drowsy to drive safely.