Celestial risk factors in groin hernia repair and random statistical association: a nationwide register-based study.

Aim: We aimed to investigate how celestial phenomena like zodiac signs, lunar phases, and Friday the 13th impacted the risk of reoperation after groin hernia repair.

Methods: We conducted a nationwide register-based study based on the Danish Hernia Database and Danish Patient Safety Authority's Online Register between 2000-2019. We included patients ≥18 years undergoing open Lichtenstein or laparoscopic groin hernia repair. The main outcomes were risk of reoperation after groin hernia repair in relation to patient and surgeon zodiac sign, lunar phase at the time of the repair, and Friday the 13th vs other Fridays.

Results: 151,901 groin hernias were included in the analysis of patient zodiac sign, and 25,075 groin hernias were included in the analysis of surgeon zodiac sign. Compared with the Sagittarius, there was a significantly higher risk of reoperation (HR [95% CI]) if the performing surgeon was born under the Capricorn (1.93 [1.16-3.12]); Pisces (1.68 [1.09-2.57]); Aries (1.61 [1.07-2.38]); Taurus (1.62 [1.04-2.54]); Cancer (2.21 [1.48-3.28]); or Virgo (1.71 [1.13-2.59]). Repairs performed under the waxing (1.23 [1.03-1.46]) and the new moon (1.54 [1.11-2.13]) had significantly higher risk of reoperation (HR [95% CI]) compared with the waning moon. Neither patient zodiac sign nor Friday the 13th affected risk of reoperation after groin hernia repair.

Conclusions: Surgeons' zodiac sign and lunar phase significantly affected the risk of reoperation after groin hernia repair. Neither patients' zodiac sign nor Friday the 13th influenced on the risk of reoperation after groin hernia repair. This indicates why significant findings should be considered carefully to distinguish between random statistical association and cause-and-effect relations.