 There is speculation that drugs used in horse racing in the United States, which are banned elsewhere, are responsible for the higher death rate in the United States.In the Canadian province of Ontario, a study of 1,709 racehorse deaths between 2003 and 2015 found that the majority of deaths were attributable to "damage during exercise to the horses' musculoskeletal system", including fractures, dislocations, and tendon ruptures.Mortality rates were eight times higher for thoroughbreds than standardbreds, and highest amongst young horses.