Survival analysis approach to risk factors associated with hyperlipemia in donkeys

Abstract

Objective - To investigate the effect of gender, body condition, and age as risk factors for the development of hyperlipemia in a population of donkeys. Design - Retrospective survival analysis. Animals - 130 donkeys with hyperlipemia from a source population of 4,126 donkeys. Procedure - A Kaplan-Meier product limit survival method was used to evaluate the effect of gender and body condition on the probability of diagnosis of clinical hyperlipemia. Cox's proportional hazard model was used to evaluate the risk of being diagnosed with hyperlipemia controlling for gender, body condition, and age at entry into the population. Results - Female donkeys and donkeys of obese body condition were more at risk for developing hyperlipemia than males or those of moderate or poor body condition, respectively. None of the females in the study was pregnant. Donkeys were more likely to become hyperlipemic soon after entering the source population. Investigation of the effect of age at entry into the population indicated that older animals were at higher risk than younger animals and, controlling for age, the hazard ratios associated with being female and being overweight were 2 and 1.5, respectively. Clinical Implications - Although pregnancy and lactation are widely acknowledged as risk factors for hyperlipemia, in this population, females and obese donkeys were at highest risk, regardless of pregnancy status. Risk was greatest around the time donkeys first entered the source population. Control of body condition, reduction of stress, and close monitoring of high-risk donkeys might reduce incidences of, or allow more timely intervention for, this potentially fatal condition.