When traveling to other countries, you expect different foods, customs and languages.
Researchers from the University of Michigan in Ann Arbor, Michigan, developed a smartphone app, Entrain, to collect data on sleep and wake times around the world, according to an abstract published in the May 6 issue of Science.
Researchers found that cultural norms determine bedtimes and wake times more than circadian rhythms. For example, women in Australia and Belgium go to bed the earliest, retiring around 10:30 p.m. and waking the next morning a little before 7 a.m. Women in Spain and Singapore, on the other hand, get to bed around midnight and rise between 7:30 and 8 a.m. American women have the fourth earliest bedtime and American men, the sixth, as well as some of the earliest wake times.
However, some sleep habits are true across nationalities. Those who are exposed to more outdoor light during the day go to bed earlier and sleep longer, the abstract notes. Women tend to schedule more sleep, and age plays a role in sleep timing—children go to bed and wake up early, teens go to bed late and sleep long hours, and adults go to sleep earlier and wake earlier as they age.