Risk factors for epistaxis on British racecourses: evidence for locomotory impact-induced trauma contributing to the aetiology of exercise-induced pulmonary haemorrhage.
BACKGROUND
The proposed biological mechanisms for exercise-induced pulmonary haemorrhage (EIPH) are many and varied. Better knowledge of risk factors should lead to achievable measures to reduce the incidence.


OBJECTIVE
To identify risk factors associated with epistaxis following racing in UK Thoroughbreds, to gain possible insights into the pathogenesis of the condition and to investigate the association between epistaxis and race finishing position.


METHODS
The association of epistaxis occurring on UK racecourses between 1996 and 1998 with a wide range of race-, horse- and start-level variables was examined in multivariable mixed effect logistic regression analyses. Four multivariable analyses were conducted, one for all race types considered collectively and one each for flat, hurdle and steeplechase race types considered separately.


RESULTS
Risk of epistaxis was significantly increased for hurdle and steeplechase race types compared to both flat and National Hunt flat races. In 3 of the 4 final models, there was a significant biological trend for increasing risk of epistaxis with increasing ground hardness ('going') and accumulated years spent racing. However, in flat races epistaxis was such a rare outcome (0.33 cases per 1000 starts) that this subset analysis had insufficient power to measure the detectable effect of 'going' as statistically significant. Horses with epistaxis were significantly more likely to have a poorer finishing position than those without blood at the nostrils.


CONCLUSIONS
Findings were consistent with the theory that locomotory impact-induced trauma contributes to exercise-induced epistaxis. Further validation of this hypothesis through application of similar methods to endoscopically visible EIPH and through biomechanical studies is warranted.


CONCLUSIONS
Knowledge of significant risk factors should allow formulation of practical measures, such as track watering, to reduce the risks of EIPH and epistaxis in racehorses.
Newton
J R
JR
Animal Health Trust, Lanwades Park, Kenftord, Newmarket, Suffolk CB8 7UU, UK.
Rogers
K
K
Marlin
D J
DJ
Wood
J L N
JL
Williams
R B
RB
D000818:Animals; D016022:Case-Control Studies; D004844:Epistaxis / Q000453:epidemiology / Q000209:etiology / Q000662:veterinary*; D005260:Female; D006470:Hemorrhage / Q000453:epidemiology / Q000209:etiology / Q000662:veterinary; D006734:Horse Diseases / Q000453:epidemiology* / Q000209:etiology; D006736:Horses; D016015:Logistic Models; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology; D012307:Risk Factors; D012420:Running / Q000502:physiology; D012621:Seasons