Sleep Duration

Research summary

• 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.
• This pattern replicates across several large, independent dose-response meta-analyses spanning different populations and time periods, which is a strong form of evidence in observational sleep research.
• The main open questions are around the exact optimal range and why long sleep duration is associated with risk (whether it reflects underlying illness rather than causing harm), which the reviewed literature itself flags as unresolved.