116 Incidence of colic and lunar phase

Abstract

Equine colic is defined as pain in the abdominal cavity; the etiology is commonly gastrointestinal. There is no known definitive cause, but conditions such as poor forage, poor dentition, parasites, or reduced water intake increase the risk of colic. Previous research on a small scale showed there is a weak but significant increase in the incidence of colic with the waxing gibbous and full moon. The objective of this study was to determine if the association between the incidence of colic and lunar phase was repeatable on a larger scale. Data on yearly equine admissions from Marion duPont Scott Equine Medical Center (2133 admissions) and Cornell University College of Veterinary Medicine Equine Hospital (1429 admissions) was aggregated, and the number of daily colic diagnoses was standardized into the number of daily colic diagnoses per 1000 yearly hospital admissions. Referred colic cases were confirmed by attending veterinarians. The corresponding moon phases were distributed into 3 levels: new moon + 2 d (n = 480), full moon + 2 d (n = 470) and remaining normal days (n = 1,850) and for each phase, the mean number of daily colic diagnoses per 1000 yearly admissions was foundto be 0.294 (SD = 0.478), 0.290 (SD = 0.463) and 0.304 (SD = 0.486), respectively. A priori power analysis showed the sample size was adequate to test the hypothesis (Statistical Power = 80%, α = 0.05). The data were strongly right skewed with multiple outliers, driving the decision to use the median and interquartile range (IQR) to represent the measure of center and dispersion and a Kruskal-Wallis H test for statistical analysis. The distribution of the number of colic cases per day were similar across all moon phases, as assessed by visual inspection of comparative boxplots. For all 3 lunar phases, the median number of daily colic diagnoses per 1000 yearly hospital admissions was 0 (IQR = 0.47). At the 0.05 significance level, there were no significant differences found in the median number of daily diagnoses per 1000 yearly admissions among the 3 lunar phases (χ2(2) = 0.261, P = 0.878). In conclusion, this data does not find an association between the incidence of referred colic cases and lunar phase.