The shortest sleep was observed in Asian countries. A new study has found that the duration and timing of sleep vary depending on age, gender and region where they live. "It was interesting to find that the circadian rhythm shifts later even in people over 20 years of age. It was already previously known that sleep timing is delayed in adolescence. What was clearly highlighted in this study is how long into adulthood this actually carries on," said Liisa Kuula, a postdoctoral researcher at the University of Helsinki. People in Europe and North America slept the longest, while the shortest sleep was observed in Asian countries. Sleep was timed the latest in the Middle East, while the earliest sleep rhythm was found in Oceania. Young women slept more than young men, and the former also went to sleep earlier. "Geographical differences were relatively small but similar to those seen in prior, smaller-scale studies. The need for sleep does not vary greatly between cultures, but differences arise in terms of the time reserved for sleeping," Kuula noted. In the study, published in the -- Sleep Medicine --journal, the sleeping habits of more than 17,000 adolescents and young adults were monitored for two weeks. The monitoring was carried out with the help of Polar Electro devices worn by the study subjects, measuring sleep with accelerometers, among other technologies. The subjects gave consent for using their personal data for research purposes, with the data being processed in anonymised form. "We gained an exceptionally diverse and extensive dataset which provides important basic knowledge on sleep among different age groups across the globe. Validated consumer devices may hold the potential for investigations more comprehensive than those conducted with conventional data collection methods," Kuula said.