Nighttime is associated with decreased survival for out of hospital cardiac arrests: A meta-analysis of observational studies

Introduction: The relationship between time of day and the clinical outcomes of patients with out-of-hospital cardiac arrest (OHCA) remains inconclusive. We undertook a meta-analysis to assess the available evidence on the relationship between nighttime and prognosis for patients with OHCA.

Materials and methods: PubMed and EMBASE were searched through June 20, 2018, to identify all studies assessing the relationship between nighttime and prognosis for patients with OHCA. Random effects modes were used to estimate odds ratios (ORs) with 95% confidence intervals (CIs).

Results: Eight observational studies met the inclusion criteria. Meta-analysis of 8 studies showed that compared with nighttime, the daytime OHCA patients had higher 1-month/in-hospital survival (OR, 1.25; 95% CI, 1.15-1.37; P = 0.00), with high heterogeneity among the studies (I² = 82.8%, P = 0.00).

Conclusions: Patients who experienced OHCA during the nighttime had lower 1-month/in-hospital survival than those with daytime OHCA. In addition to arrest event and pre-hospital care factors, patients' comorbidity and hospital-based care may also be responsible for lower survival at night.