The effect of Friday the 13th and Full Moons on cardiac transplantation is unknown. We investigated the impact of these superstitious events on recipient and donor qualities, complications, survival, and volume.

All adult transplants from 2013-2023 in the United Network for Organ Sharing database were retrospectively reviewed. Friday the 13th recipients were compared to Adjacent Friday recipients and all other recipients. Full Moon recipients were compared to New Moon recipients and all other transplants. Recipient and donor characteristics were statistically compared, and outcomes including transplant volume, frequency, complications, and survival were assessed between groups before, and after, the 2018 allocation change.

One thousand and twenty transplants occurred on a Full Moon, and 134 occurred on a Friday the 13th. No differences between donors, recipients, or outcomes and volume across eras were found in the Lunar analysis (all p > 0.05). Compared to Adjacent Friday recipients, but not to the control group, Friday the 13th recipients had higher rates of severe functional impairment (44% vs 41%), longer admissions before transplant (4 vs 1 day), and a higher prevalence of intensive care unit placement (40% vs 35%) (all p < 0.05). However, no differences were found in donor characteristics, outcomes, survival, or volume in either era (all p > 0.05).

There is likely no substantial adverse or unlucky influence of the Full Moon or Friday the 13th on cardiac transplantation. However, perceived stress has demonstrated effects on medical outcomes and health system functioning. Therefore, further research should investigate the persistence of these beliefs in health care settings.