Key finding
U-shaped; ~7 h/night lowest risk; 9–11 h associated with materially higher mortality in meta-analysis
Evidence & causal status
Strong
Association
Caveats & limitations
Reliability / bias notes: Illness causing long sleep; sleep apnea; shift work; self-report
This describes a population-level association from published research. It is not a prediction about any one individual, and association is not the same as causation unless stated otherwise above.