title: Appointments at a thyroid outpatient clinic and the lunar cycle.
abstract: BACKGROUND
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Nuclear Medicine, Ludwig Boltzmann Institute of Nuclear Medicine, University of Vienna, Vienna, Austria. georg.zettinig@univie.ac.at
authors.forename: Georg
authors.initials: G
authors.lastname: Zettinig
authors.forename: Richard
authors.initials: R
authors.lastname: Crevenna
authors.forename: Christian
authors.initials: C
authors.lastname: Pirich
authors.forename: Robert
authors.initials: R
authors.lastname: Dudczak
authors.forename: Thomas
authors.initials: T
authors.lastname: Waldhoer
mesh_terms: D001071:Appointments and Schedules; D001317:Austria; D006801:Humans; D016081:Moon; D017711:Nonlinear Dynamics; D010044:Outpatient Clinics, Hospital / Q000706:statistics & numerical data*; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data; D010507:Periodicity; D012044:Regression Analysis; D013959:Thyroid Diseases / Q000453:epidemiology*