Mortality and life table analysis in a young cohort of pet cats in the UK

Abstract

Objectives: Mortality data represent an important resource for understanding population health that previously have mostly been extrapolated from veterinary records. The aims of this study were to explore mortality for a cohort of pet cats in the UK using data from owner-completed questionnaires, thus potentially representing a more comprehensive population, and to determine the all-cause mortality and survival probabilities. Methods: Data were collated from the ‘Bristol Cats’ study questionnaires, owner communications and medical records for the cohort’s first 8 years of life. Mortality was classified by organ system, disease or event, and analysed by age and life stage. Age-specific mortality and cumulative survival probability curves were constructed using life table analysis. Results: Of 2444 cats recruited into the ‘Bristol Cats’ study, at least 362 died before reaching the age of 9 years. The most common cause of death in cats up to the age of 8 years was road traffic accident (RTA; 45.6%). For kittens (aged <1 year), the most common causes were RTA (61.2%), feline infectious peritonitis (11.9%) and other trauma (7.5%). The most common causes of mortality in young adult cats (aged 1–6 years) were RTA (49.6%), non-specified (14.4%), renal disease (6.5%) and cardiovascular disease (6.5%). Cats aged up to 2 years had an annual probability of dying in the range of 2.8–3.1%, which decreased between 2 and 3 years of age to 1.7%. Thereafter, the probability of dying gradually increased with age, with the oldest age group (aged 7–8 years) having a 3.6% probability of dying. Conclusions and relevance: This study identified important differences in causes of mortality for the first two life stages in a population of cats that may not be fully accounted for in medical records. Life table analysis documented an increasing probability of death with age after year interval 2–3 with a higher mortality risk for cats aged up to 2 years.