JAMA Netw Open
Nighttime cardiac arrests still have worse survival
Clinical takeaway: Nighttime out-of-hospital cardiac arrest may need targeted quality improvement beyond response-time reduction including bystander recognition, cardiopulmonary resuscitation quality, defibrillation access, and post-resuscitation care.
Out-of-hospital cardiac arrests at night have long been linked to worse outcomes, but it was unclear whether that gap has continued to persist in contemporary U.S. care. This study tested whether nighttime response was still associated with lower survival and whether emergency care factors explained the difference.
The nighttime survival gap appears to be only partly about slower emergency response. Median response time was 48 seconds longer at night than during the day — 7.0 vs 6.2 minutes — but that difference explained only 12.6% of the survival disadvantage, suggesting other factors may matter, including bystander recognition, cardiopulmonary resuscitation quality, automated external defibrillator access, time to defibrillation or epinephrine, and post-resuscitation hospital care.
Sustained return of spontaneous circulation occurred in 25.8% of nighttime cases vs. 30.6% of daytime cases, and neurologically favorable survival occurred in 6.7% vs. 9.3%, respectively. After adjustment, nighttime response was associated with 15% lower odds of sustained return of spontaneous circulation and 16% lower odds of neurologically favorable survival.
The disadvantage persisted in clinically favorable subgroups. Among bystander-witnessed arrests with an initially shockable rhythm, neurologically favorable survival was 23.0% at night vs. 30.0% during the day. Among patients with sustained return of spontaneous circulation, neurologically favorable post-resuscitation survival was also lower at night, at 24.5% vs. 29.1%.
Researchers analyzed 874,415 adults in the Cardiac Arrest Registry to Enhance Survival from 2013 to 2024. Nighttime response was defined by prehospital dispatch time from 11 p.m. to 6:59 a.m.; 27.7% of emergency responses for out-of-hospital cardiac arrest occurred during that window.
“This nighttime survival disadvantage has persisted without improvement for more than a decade,” the authors concluded, adding that “the prehospital response interval only acted as a partial mediator between nighttime and survival.”
Source: Kimbrell JM. JAMA Netw Open. 2026 Apr 29. Out-of-Hospital Cardiac Arrest Survival at Nighttime