Lasix identified among risk factors associated with sudden death in thoroughbred racehorses
by Mary Guiden
Researchers from the universities of Glasgow and Bristol studied risk factors associated with race-related sudden death in Thoroughbred racehorses in the U.S. and Canada. Among the findings, the team found horses racing while on furosemide medication or Lasix — an anti-bleeding medication — were at 62% increased odds of sudden death.
The study, “Fifteen risk factors associated with sudden death in thoroughbred racehorses in North America (2009–2021),” was published online Oct. 20 in the Journal of the American Veterinary Medical Association.
Euan Bennet, lecturer in the School of Biodiversity, One Health and Veterinary Medicine at the University of Glasgow, and Tim Parkin, professor of veterinary epidemiology at the University of Bristol, extracted data from the Equine Injury Database, which contains detailed records of more than 92% of all official race starts made in the U.S. and Canada.
The researchers identified 4.2 million race starts made by 284,387 thoroughbred horses at 144 racetracks in the U.S. and Canada during the study period between 2009 to 2021.
In recent years Santa Anita Park in California established new regulations that horses race without race-day medication, except for Lasix, which is now a maximum of 50% of the levels established in 2019.
The park, which has been scrutinized following 42 horse deaths in 2019, said that two-year-old horses are required to race medication-free, including Lasix. Eleven horses have died at Santa Anita in 2022; the most recent death occurred last month, following a collision on Oct. 21 between two horses.
Procedures
Bennet and Parkin analyzed 49 potential risk factors using univariable and multivariable logistic regression. Cases were defined as race starts that resulted in fatality within three days of racing, in which at least one of five codes relating to sudden death was recorded. Fatalities due to catastrophic musculoskeletal injury were omitted from the study cohort.
Results
The authors found 536 race starts resulted in sudden death, an incidence rate of 0.13 per 1,000 starts. Fifteen risk factors were significantly associated with sudden death, including horse age and sex, season and purse of race, race distance and horses’ recent history of injury and lay-up. Horses racing while on furosemide medication were at 62% increased odds of sudden death.
Clinical relevance
Associations found between previous injury and sudden death suggests preexisting pathology could contribute in some cases. The association between furosemide and sudden death prompts further study to understand which biological processes could contribute to this result.
Euan Bennet and Tim D. H. Parkin. "Fifteen risk factors associated with sudden death in Thoroughbred racehorses in North America (2009–2021)." Journal of the American Veterinary Medical Association. JAVMA 20 Oct 2022 DOI: https://doi.org/10.2460/javma.22.08.0358
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