This study examines the association between sleep duration, multimorbidity, and mortality using data from the 2004 National Health Interview Survey (NHIS) linked to the National Death Index through 2019. Cox proportional hazards models were employed to assess the impact of sleep duration on mortality risk across different comorbidity groups. Findings indicate a J-shaped relationship, with both short (≤4 hours) and long (≥9 hours) sleep durations associated with increased mortality, particularly among individuals with multimorbidity. The highest hazard ratios (HRs) were observed in those with ≥3 diseases and excessive sleep durations, especially in cardiovascular and respiratory conditions. Shorter sleep (5–6 hours) exhibited a protective effect in some multimorbidity categories. These results highlight the importance of individualized sleep recommendations based on health status. Future research should explore causal mechanisms and personalized interventions to optimize sleep duration in at-risk populations.
