Investigating the relationship between inbreeding and life expectancy in dogs: mongrels live longer than pure breeds

This study aimed to investigate the establishment of relationship between inbreeding and life expectancy in dogs. A dataset of N = 30,563 dogs sourced from the VetCompass™ Program, UK was made available by the Royal Veterinary College, University of London, containing information about breed and longevity and was subject to survival analysis. A Cox regression proportional hazards model was used to differentiate survivability in three groups of dogs (mongrel, cross-bred and pure breed). The model was found highly significant (p < 0.001) and we found that mongrel dog had the highest life expectancy, followed by cross-bred dogs with only one purebred ancestor and purebred dogs had the lowest life expectancy. A second Cox regression was also found highly significant (p < 0.001) differentiating the lifespan of different dog breed and correlating positively the hazard ratio and the Genetic Illness Severity Index for Dogs (GISID). The results show that survivability is higher in mongrel dogs followed by cross-bred with one of the ancestor only as a pure breed, and pure breed dog have the highest morbidity level. Higher morbidity is associated with higher GISID scores, and therefore, higher inbreeding coefficients. These findings have important implications for dog breeders, owners, and animal welfare organizations seeking to promote healthier, longer-lived dogs.