Determinants of unwitnessed out-of-hospital cardiac arrest: a systematic review (HL-D-26-00618).
Heart & lung · 2026-10-08 · Systematic review
Abstract
BACKGROUND: Approximately half of all out-of-hospital cardiac arrest (OHCA) cases are unwitnessed, with survival rates below 5%. Although early recognition is critical for improving outcomes, factors associated with unwitnessed OHCA have not been systematically reviewed. OBJECTIVES: To systematically review and synthesize the available evidence on determinants of unwitnessed OHCA. METHODS: We included peer-reviewed observational studies investigating associations between demographic, socioeconomic, clinical, or situational factors and witnessed status of OHCA in adults. No restrictions were placed on setting, language, or publication year. A systematic search of MEDLINE, Embase, and Web of Science Core Collection was performed from inception to July 17, 2025. Risk of bias was assessed using the QUIPS tool. Findings were synthesized narratively by determinant domain, summarizing study counts, effect directions, statistical significance, and consistency. RESULTS: Twenty-two studies including 210,028 individuals were analyzed. Female sex and arrest occurring at home were most consistently associated with unwitnessed OHCA. Limited evidence, predominantly from unadjusted analyses, suggested higher rates of unwitnessed OHCA among Black individuals, those with low socioeconomic status or living in more deprived areas, individuals with type I diabetes, psychiatric illness, and arrests occurring at night, during sleep, or in residential or rural settings. CONCLUSION: This systematic review identified several factors associated with unwitnessed OHCA, with the most consistent evidence for female sex and arrests occurring at home. These findings may help guide targeted prevention and public health strategies.
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Tags
Equity & disparities · Sex & gender
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