Evaluation of age, breed, and gender as risk factors for umbilical hernia in horses of a hospital population.

Age, breed, and gender distributions of 168 horses with umbilical hernia treated at the University of Pennsylvania School of Veterinary Medicine were analyzed to determine risk factors for this disease. For the 3 breeds that constituted the largest proportion of hospital and case populations, Thoroughbred, Standardbred, and Quarter Horse, the overall ratio of females to males was 1.63. In a hospital population of the same age group, 0 to 48 months, the female to male ratio was 0.93. Compared with males, females were at significantly higher risk for umbilical hernia after adjustment for breed and age (odds ratio, 2.01; 99% confidence interval, 1.31 to 3.10; P = 0.00002). Of the 2 major breeds, Thoroughbreds were at greater risk than Standardbreds for umbilical hernia, after adjustment for gender and age (odds ratio, 1.80; 99% confidence interval, 1.10 to 2.95; P = 0.0020). The results provide information about a common congenital defect in horses that can be used for future genetic research.