Long-term health and predictors of survival for hyperthyroid cats treated with iodine 131

Two hundred thirty-one cats treated with radioactive iodine at the Texas Ve terinary Medical Teaching Hospital were followed for a median of 25 months by means of an ambidirectional (prospective, retrospective) cohort study de sign. Cox proportional hazards models were used to determine predictors of survival based on data at the time of hyperrhyroid diagnosis (collected ret rospectively) and found that only age at diagnosis and sex of the cat were predictors of survival. Increasing age (for each year of age, relative risk [RR] = 1.2, 95% confidence interval [CI] = 1.1-1.3) and being male (RR = 0 .68, 95% CI = 0.5-0.9) increased likelihood of death. Tables predicting sur vival after diagnosis and treatment of hyperthyroidism for various age and sex combinations were created. In addition, Cox proportional hazard models were run with all data available at the end of the study (collected retrosp ectively and prospectively) including number and type of major health probl ems reported at the time of death or censoring. In this model, significant factors were age at diagnosis, sex, and either type of major health problem or number of health problems. Cats with renal disease or cancer were more likely not to survive and increasing from none to 2 health problems also de creased survival. Renal problems and cancer were the most common health pro blems at the time of death or censoring. This study provides estimates of d uration of survival for cats successfully treated for hyperthyroidism with radioactive iodine, which can be useful in assisting with client treatment decisions.