On 9/26/07, Shyam Visweswaran <[EMAIL PROTECTED]> wrote: > No variance measure is mentioned; perhaps the > original article does. Without a variance measure > it is hard to estimate how far 8 hrs is removed > from 7 hrs.
Whithout reading the original study it's hard to say for sure, but it looks like they have just shown correlation, not causality. There may be a common reason for less sleep, higher mortality (heart disease makes it harder to sleep?) or more sleep, higher mortality (apnea?) anyway. -- Charles
