> But 8-9 hours of sleep nightly - my guess would be that people who get only 7 hours of sleep tend to be more successful, have jobs and families, and access to

> But 8-9 hours of sleep nightly - my guess would be that people who get only 7 hours of sleep tend to be more successful, have jobs and families, and access to health care. Whereas those sleeping 10 hours a night are less likely to have the income to get health care when necessary. I'd hope that such studies on sleep control for income, employment, education and what not.