Figure 7.

Odds ratios (OR) for contrasts between combinations of track and surface (TS) and horse age (AGE) and describing an AGE*TS interaction identified in multivariable logistic regression modelling of fatalities in Ontario Thoroughbred racehorses for the period 2003–2015, unit of interest—workout event by horse-year. For OR values above 1, the numerator odds of fatality are higher than the denominator odds. The pattern for each comparison is for OR to rise as AGE increases and reflects progressively increasing fatality with age in the numerator. The effect is most marked for workouts on turf at Track 1, which show a very high liability for older horses. No workouts were recorded on turf at Track 2. (Note log scale on y-axis.) Confidence intervals that include 1.0 are non-significant.