Risk factors for race-associated sudden death in Thoroughbred racehorses in the UK (2000-2007).

REASONS FOR PERFORMING STUDY Sudden death adversely affects racehorse welfare, jockey safety and the public perception of horseracing. OBJECTIVE To describe the risk of racing-associated sudden death in Thoroughbred racehorses in the UK from 2000 to 2007, to identify whether there were risk factors uniquely associated with sudden death and to improve the understanding of the pathogenesis of racing-associated sudden death by identification of risk factors for such cases. METHODS A sudden death was defined as an acute collapse and death, in an apparently healthy Thoroughbred racehorse, during or immediately after racing, in the absence of clinical data indicative of a catastrophic orthopaedic injury. The retrospective study included 201 case race starts and 705,712 control race starts. Univariable and multivariable logistic regression were used to identify risk factors for sudden death at any one start. RESULTS In the multivariable model, age, distance, race type, season and number of starts in the 60 days prior to the race were associated with sudden death. CONCLUSIONS The risk factors identified in this study are not uniquely associated with sudden death and have been also been identified in studies using all causes of fatality as the outcome. These data suggest that a generic approach to reduce fatal musculoskeletal injury and sudden death may be possible. POTENTIAL RELEVANCE The identification of risk factors allows speculation on the underlying mechanisms of sudden death in racing. This may stimulate hypothesis-led investigations into the pathogenesis of exercise-related arrhythmias, exercise-induced pulmonary haemorrhage and blood vessel rupture.