2015 ACVIM Forum Research Abstract Program

Five-hundred fifteen of nine-hundred eighty two horses with complete epidemiological information were included in the final data analysis. Of the 515 horses, 222 (43%) were PPID + , 203 (39.4%) were IR + . Further, horses were stratified into 1 of 4 groups based on ACTH and insulin laboratory results (PPID + / IR -), (PPID + /IR + ), (PPID -/IR + ), and (PPID -/IR -). Of the 515 horses, 115 (22.3%) were PPID + /IR -, 97 (18.8%) were PPID + / IR + , 106 (20.6%) were PPID -/IR + , and 197 (38.3%) were (PPID -/IR -). Of the 515 horses evaluated, 18.5% of horses <15 years of age were PPID + , 33% of horses 15 to 19.9 years of age were PPID + , 56.3% of horses 20 to 24.9 years of age were PPID + , and 74% of horses >25 years of age were PPID + . In particular, the odds of PPID for horses between 15 and 19.9 years of age was approximately twice (2.2) that for horse <15 years old. Compared to horses in the youngest age group, the odds ratio (OR) for PPID increased to 4.6 for horses between 20 and 24.9 years of age and to 14.0 for horses ≥25 years of age. Even after adjusting for the age of the horses, insulin-resistant horses were seen to have approximately twice the odds (1.9) of PPID compared to horses with normal insulin levels.