Although many factors influence how much sleep you really need, most young adults report sleeping about seven and a half hours on weekday nights and eight and a half hours on weekend nights. And the common recommendation is eight hours a night. But individual needs vary greatly. There are so-called short-sleepers and long-sleepers -- those who need as little as five and a half hours to as much as about nine and a half hours.
How much sleep you require depends on several factors including:
- Your inherited genetic need
- Your sleep hygiene (those daily activities you control, from drinking coffee or alcohol to smoking and exercise)
- The quality of your sleep
- Your 24-hour daily cycle known as the circadian rhythm
For example, smoking, drinking, and exercise can affect your sleep dramatically. What you actually do in bed (like reading or watching TV) and how much exposure to light you have (looking at that bright computer screen 'til midnight) will also significantly alter both the quality and quantity of your sleep. They all interact to determine how long you need to sleep to wake up feeling refreshed and remain alert throughout the day.
How did we get the age-old recommendation that we need a solid eight hours of sleep? In a classic study, researchers placed a volunteer in windowless, light-controlled room for 30 days. The light was on for 16 hours and off for eight hours, but the study participant could also turn the lights on and off at will.
Before the experiment began, the subject routinely got about six and a half hours of sleep. During the first night of the experiment he slept eight hours, the second night 10 hours, the third night 12 hours, and the fourth night 14 hours. Over the next several days, he began to reduce the number of hours slept, eventually falling to a steady eight hours and 13 minutes. This experiment was performed repeatedly with all types of people, with similar results, and this is where the recommendation of eight hours comes from.
