A study, reported recently in Current Biology, examined why adolescents go to bed later. Researchers in Germany asked 25,000 individuals (from 8 to 90 years of age) about their sleep and wake times. Based on the participants'responses, the researchers mapped their "chronotypes" (an individual's endogenous or natural circadian clock "synchronises"or alignments to the 24-hour day).
The results of the study indicated that children are early chronotypes and become progressively later during development, reaching a maximum lateness around age 20, when they become earlier again. A comparison of men and women showed that women reached their maximum lateness earlier (19.5, compared with 20.9 years in men). The results further suggested that women mature faster than men.