I understand this is correlation not causation, but we have tons and tons of evidence for the negative effects of sleep deprivation.
Color me highly skeptical that there are negative effects associated with sleeping 8.5+ hours, up to say, 11 hours. Beyond 11 hours of sleep, I can see an argument being made for physical morbidity from lack of movement etc. 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.
In other words, I'd be interested to see studies which test the hypothesis that sleep deprivation has a causal effect on morbidity, while excessive sleep only has a correlation.
Color me highly skeptical that there are negative effects associated with sleeping 8.5+ hours, up to say, 11 hours. Beyond 11 hours of sleep, I can see an argument being made for physical morbidity from lack of movement etc. 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.
In other words, I'd be interested to see studies which test the hypothesis that sleep deprivation has a causal effect on morbidity, while excessive sleep only has a correlation.