The dangers look especially serious for the female population. A university of California study of the sleeping habits of 459 women aged between 50 and 81 showed that those who got between 5 and 6.5 hours of sleep lived longer than those who got less. Interestingly, the research, which was publishd in 2010, showed those who got more than this optinum amount also had shorter lifespans. However, in the case of young people, it seems that a desire for more sleep might be justified. Research by Harvard University in 2008 indicated that people in the 18-32 bracket were comfortable with 9 hours of sleep. Participants aged 60-72, on the other hand, needed no more than 7.5 hours.