Life expectancy and survival analysis for companion dogs and cats in Seoul, South Korea

Abstract

Background: Investigating life expectancy and mortality is crucial for the development of evidence-based health strategies for companion animals. However, relevant studies are lacking in South Korea, possibly because of challenges in collecting mortality data. In this regard, preliminary analyses were conducted to obtain life tables for companion animals in South Korea.

Methods: The electronic records of six veterinary hospitals in Seoul, South Korea were examined. The data collected included breed, sex, spay/neuter status, date of birth, and date of death for all dogs and cats with a verifiable date of death since November 1, 2004 until December 31, 2022. After data preprocessing, descriptive statistical analysis was performed to summarize the demographics, and life tables and survival curves were created for dogs and cats. Cox proportional hazards regression was used to analyze the effects of demographic factors on survival.

Results: The mean age of dogs at death was 3427.49 days. Spayed or neutered dogs had a significantly higher life expectancy than intact dogs. Mixed-breed dogs had a higher life expectancy than purebred dogs. For cats, the mean age at death was 1965.49 days, with spayed or neutered cats living significantly longer than intact cats. Purebred cats had a higher median survival than Mixed-breed cats. Spaying or neutering and breed significantly affected survival probabilities in both species.

Conclusion: Our study provides insights into the longevity of companion animals in South Korea, and reveals that neutering and breed significantly influence life expectancy.

Keywords: companion cats; companion dogs; life expectancy; life tables; survival analysis.

Figure 1

Kaplan Meier curve of the entire study population of dogs and cats. (A) The Kaplan–Meier curves for dogs, (B) for cats. The horizontal axis shows the age of the dogs or cats and the vertical axis shows the cumulative survival probability by age of the dogs or cats. The red graph shows the Kaplan Meier curve for dogs and the blue graph for cats. The shading around the graphs represents the 95% confidence intervals. The vertical and horizontal dashed lines represent median survival.

Figure 2

Kaplan Meier curves for dogs survival based on sex, breed, and spay/neuter status. The horizontal axis shows the age of the dogs in the subgroup and the vertical axis shows the cumulative survival probability by age of the dogs. (A) Shows the Kaplan–Meier curves for dogs by sex, (B) for dogs by breed, (C) for male dogs by neuter status, (D) for female dogs by spay status. In the upper right corner of each subfigure, the p-value of the Log-rank test performed on each subgroup is shown.

Figure 3

Kaplan Meier curves for cats survival based on sex, breed, and spay/neuter status. The horizontal axis shows the age of the cats in the subgroup and the vertical axis shows the cumulative survival probability by age of the cats. (A) Shows the Kaplan–Meier curves for cats by sex, (B) for cats by breed, (C) for male cats by neuter status, (D) for female cats by spay status. In the upper right corner of each subfigure, the p-value of the Log-rank test performed on each subgroup is shown.

Figure 4

Cox regression analysis for dogs and cats based on spay/neuter status, sex, and breed. (A) Is a forest plot of the hazard ratio of dogs by spay/neuter status, sex, and breed. (B) Is a forest plot of the hazard ratio of cats by spay/neuter status, sex, and breed. In each subfigure, the horizontal axis shows the hazard ratio. The black squares represent point estimates of the hazard ratio for each subgroup, and the horizontal line across the black squares represents the 95% confidence interval.