1. 9% higher out-of-hospital cardiac arrest risk on the first weekday after holidays vs other weekdays.
2. Risk spike occurred only on the first postholiday day.
3. Adults >65 years showed greater vulnerability.
4. Cardiac-origin arrests and nonshockable rhythms were most associated.
5. Two or more consecutive holidays increased risk; single-day holidays did not.

Source: JAMA Network Open