How many studies support Sleep Duration?

Sleep duration and mortality risk is one of the more extensively meta-analyzed relationships in sleep research, with multiple independent meta-analyses of prospective cohorts consistently finding a U-shaped relationship: both short and long habitual sleep are associated with higher all-cause and cardiovascular mortality compared to moderate durations. That's backed by 7 published studies in Vitaebase's database, including 2 meta-analyses, the most recent from 2026 -- a modest but real research base.