Circadian Regulation of Sleep in Habitual Short Sleepers and Long Sleepers

Routine sleep duration varies greatly among individuals. The biological meaning of this variation is unknown. The term circadian rhythm refers to the biological clock that regulates the timing of falling asleep, waking up, and secretion of hormones, like melatonin. Melatonin is secreted at night. Previous studies have shown that melatonin may play a role in the regulation of sleep. The purpose of this study is to learn whether the duration of nighttime (nocturnal) melatonin secretion is longer in people with long regular sleep duration than people with short sleep duration. Researchers will compare levels of melatonin and cortisol, body temperature, sleepiness, and sleep in two extreme groups. Group one will be made up of people with short sleep duration lasting less than 6 hours. Group two will be made up of people with long sleep duration lasting more than 9 hours.