Introduction

Obesity is a nutritional disease of concern in both canine and feline pets, with up to 35% of adult dogs and cats in the United States reported to be either overweight or obese [1] [2] [3] [4]. Several chronic diseases have been associated with overweight and obesity in both dogs and cats, including osteoarthritis, heart disease, and diabetes mellitus, as well as hypothyroidism in dogs [5] [6]. This population analysis was conducted in order to provide a recent assessment of select chronic conditions as co-morbidities in the US pet population.

Methods of analysis

Medical records of all canine and feline in-patients seen in 2013 at over 850 Banfield Pet Hospitals were used to extract information regarding body condition score (using a 5-point scale, with 1 = cachexia, 3 = ideal, 5 = obese), reproductive status and diagnoses of select chronic diseases hypothesized to be linked to overweight or obesity: diabetes mellitus, heart disease (cardiomyopathy, heart failure, valvular insufficiency), osteoarthritis and hypothyroidism (dogs only). Relative risk (calculated as a prevalence ratio, i.e., the probability of being overweight if an animal has a chronic disease vs. not having the disease) and 95% confidence intervals were calculated for each chronic disease, and adjusted for spay/neuter status.

Results

In 2013, more than 463,000 cats and 2,281,000 dogs visited a Banfield hospital. The distribution of sex and neuter status for the cat population was as follows: 6.5% intact females, 5.5% intact males, 43.6% spayed females and 44.4% neutered males. The distribution in the dog population was 10.7% intact females, 14.3% intact males, 37.4% spayed females, and 37.6% neutered males.
Among the cats, 23.1% were juveniles (< 12 months of age), 20.9% young adults (1-3 years old), 37.2% mature adults (3-10 years of age), and 18.8% geriatric adults (10 years and older). Among the dogs, 22.0% were juveniles, 23.3% young adults, 44.6% mature adults, and 10.1% geriatric adults.

Overall, 30.3% of cats and 26.3% of dogs were recorded as being either overweight or obese (BCS of 4 or 5). Those diagnosed with the chronic conditions of interest were commonly overweight or obese, with the prevalence of overweight/obesity greater in animals with the chronic disease than those without the disease (Table 1). Neutered pets were more likely to be diagnosed with all conditions than intact pets (P < 0.0001 for each comparison; Table 2), with prevalence ratios in cats noticeably greater than in dogs. The relative risk of overweight or obesity in pets diagnosed with chronic disease vs. no chronic disease for osteoarthritis, heart disease and diabetes mellitus in cats are 1.39, 1.05, and 1.79 (respectively) and in dogs 1.97, 1.55, and 2.09 (respectively); the relative risk for canine hypothyroidism is 2.73. Because neuter status is associated with being overweight/obesity, the calculations were adjusted for neuter status; in brief, this involved calculating the relative risk of being overweight/obese with a given condition for the neutered population, and for the intact population, then combining the two calculations to establish the adjusted relative risk. This weighted average of the two risk groups resulted in a decrease in the magnitude of the relative risk of overweight/obesity associated with each chronic disease. With the exception of feline heart disease (p = 0.75), pets with the chronic conditions were significantly more likely to be reported as overweight or obese (P < 0.0001).

Discussion

Overweight and obese pets are at greater risk for specific chronic diseases that impact on the quality of life for the pets and their owners. The proportion of patients seen at Banfield Pet Hospital that are diagnosed with the selected chronic diseases is small; although a high proportion of patients seen at Banfield are young, the low prevalence of these chronic diseases reported here are similar to those previously reported [1] [2] [3] [7].

Multivariate analyses are needed to more fully characterize the associations between these conditions and overweight/obesity, controlling for potential confounders and other identified risk factors such as gender, age, and breed [1] [2] [5] [6]. Because of the cross-sectional nature of this study, it is not possible to determine whether the chronic conditions preceded, co-developed with, or followed an overweight or obese body condition. However, the significant associations found suggests that diagnosis of certain chronic conditions is an excellent opportunity to educate clients of the importance of nutrition and weight control in order to reduce the other risks associated with overweight and obesity.