Effect of lunar cycle on temporal variation in cardiopulmonary arrest in seven emergency departments during 11 years

Objective To determine the effect of the phase of the full and new moon on the variation in the number of daily cardiopulmonary resuscitations. Design A retrospective analysis of a computerized billing database of emergency department visits in a cohort of seven northern New Jersey (USA) emergency departments. Participants Consecutive patients seen by emergency department physicians over an 11-year period (1 January 1988 to 31 December 1998). We determined the timing of full and new moon days from the National Oceanographic and Aeronautic Administration website. Interventions Time series regression estimated the independent effect of full and new moon days on the daily variation in cardiopulmonary resuscitations. Tests of statistical significance were made at α=0.05. Results A total of 2 370 233 emergency department visits were made during the 4018-day period of study. A total of 6827 had an emergency department diagnosis of cardiopulmonary resuscitation. We found no significant difference in the occurrence of cardiopulmonary resuscitations during the full moon (P=0.97). On average there were 6.5% fewer cardiopulmonary resuscitations during new moon days (P=0.02; 95% confidence interval 1.3-11.7%). Conclusion Contrary to the traditional belief that more cardiopulmonary resuscitations occur during the full moon, we were unable to identify a significant effect during full moon days. However, there were on average 6.5% fewer cardiopulmonary resuscitations during new moon days than other days.