Introduction: Several variables of health-related human behaviour have been analysed with regard to a possible association with lunar phases. The aim of this study was to evaluate a possible relation between the lunar cycle and the number of requests for appointments at an outpatient clinic. This variable has not been studied hitherto.
Methods: We analysed a total number of 11,413 requests for appointments at our thyroid outpatient clinic during one year. Access to this clinic is not restricted, and all patients with known or suspected thyroid disease living in the area of Vienna may ask for an appointment. During the study period, 8,852 patients requested a follow-up appointment, and 2561 patients asked for a new appointment. We analysed a possible cyclic pattern in these requests using a nonlinear regression model based on both groups of patients.
Results: A cosinus curve with a period of 29.531 days (the mean length of a lunar cycle) was significantly associated with the number of requests for both follow-up appointments (p = 0.007) and new appointments (p = 0.001). Requests for follow-up appointments had their highest peaks three days after the full moon, whereas requests for new appointments were most frequent five days afterwards.
Conclusion: Our findings suggest that lunar phases may affect patients' requests for appointments at a thyroid outpatient clinic. To the best of our knowledge, this is the first study reporting a possible association between health-related behaviour and lunar phases using requests for appointments as a relevant variable. There is a need for more research into the mechanism underpinning this behaviour.