Data that has consistently shown a lower rate of fatal injuries for horses running on artificial surfaces when compared to horses running on dirt surfaces has been found to be statistically significant for the first time, according to an epidemiologist who has analyzed data on racehorse injuries.\r\nThe finding by Dr. Tim Parkin, a University of Glasgow epidemiologist who was hired by the Jockey Club to analyze injury data, is based on an analysis of 754,932 starts over the past two years. In the analysis, horses running on artificial surfaces suffered fatal breakdowns at a rate of 1.55 horses per 1,000 starts, compared to a 2.14 rate for horses starting on dirt surfaces. Overall, the rate of catastrophic injury on all surfaces, including turf, was found to be 2.00 breakdowns per 1,000 starts.\r\nINJURY DATA: Two-page supplemental analysis of the study (PDF)\r\nThe data collected as part of the Equine Injury Project has consistently shown the lower rate for artificial surfaces, but officials analyzing the data had not determined the difference to be statistically significant because of a need to collect a trove of information sizeable enough to hold up under the rigors of a statistical analysis. In scientific terms, a statistically significant difference is one that is unlikely to have occurred by chance.\r\n&ldquo;The addition of 376,000 starts to the database in year two enabled us to statistically validate certain trends in the data,&rdquo; Parkin said in a news release.\r\nThe finding is sure to reignite discussion on the relative merits of dirt surfaces and synthetic surfaces, a debate that has inflamed passions on both sides. Critics of synthetic surfaces have said that the rates are influenced by factors relating to the relative quality of the horses and that the numbers for dirt injuries are inflated by the relatively larger number of racetracks with dirt surfaces that are havens for cheaper horses at the ends of their careers. Other critics of artificial surfaces have said that the analyses ignore soft-tissue injuries on artificial surfaces.\r\nMatt Iuliano, executive vice president of the Jockey Club, said that Parkin has not yet looked at variables that would quantify the relative class levels of horses that suffer catastrophic injuries, though the data collected under the Equine Injury Project includes information on the type and purse level of the race in which the horse suffered the breakdown. In addition, the analysis has not revealed any underlying cause or trend that would go toward explaining why the rates between surfaces differ, Iuliano said.\r\n&ldquo;Dr. Parkin is, however, working on an experimental design that would address that and other variables,&rdquo; Iuliano said.\r\nParkin was not available for an interview Wednesday.\r\nArtificial surfaces have been installed at nine tracks: Keeneland and Turfway in Kentucky; Presque Isle Downs in Pennsylvania; Woodbine outside of Toronto; Arlington Park just north of Chicago; and Del Mar, Golden Gate, Hollywood Park, and Santa Anita in California. Earlier this year, Santa Anita ripped up its artificial surface and replaced it with a dirt track after encountering persistent problems maintaining the surface, especially during heavy rains.\r\nBiomechanical studies of artificial surfaces have demonstrated that horses&rsquo; limbs are subjected to less force and stress when galloping over synthetic tracks. The studies were cited by many supporters of artificial surfaces when the tracks began to be installed at major tracks four years ago. Supporters also claimed that the surfaces were largely &ldquo;maintenance-free,&rdquo; a claim whose credibility has been severely strained by the experience of racetrack maintenance crews over the past few years.\r\nThe analysis also showed that horses running over turf courses suffer fatalities at a rate of 1.74 horses per 1,000 starts. As for age groups, 2-year-olds were the least likely to suffer catastrophic injuries, at a rate of 1.51 horses per 1,000 starts, according to the analysis, while 5-year-old horses were the most likely age group to suffer a fatal injury, at 2.45 horses per 1,000 starts.\r\nThe analysis of the data also said that fatality rates continue to be unaffected by the distance a horse races, the weight it carried in the race, or whether a race was moved off the turf. In addition, fillies and mares racing in open races did not suffer fatalities at a higher rate than other horses.\r\nThe Equine Injury Database was launched more than two years ago to track racehorse injuries during racing and training, in part because of public scrutiny of racing following the death of the filly Eight Belles after the 2008 Kentucky Derby. Almost all North American racetracks have volunteered to participate in the study, but under the condition that individual fatality rates at tracks would not be made public.