The Hidden Links: How Weight, Neutering, and Age Shape OA Risk

This study, titled "Body weight, gonadectomy, and other risk factors for diagnosis of osteoarthritis in companion dogs" (Graves et al., 2023), conducted a retrospective cohort analysis of 131,140 dogs from Banfield Pet Hospitals (1998–2019) to identify key risk factors associated with the diagnosis of osteoarthritis (OA).

Key Findings

The researchers identified several significant factors that influence the risk of OA in dogs:

• Primary Risk Factors: Older age, higher adult body weight, and gonadectomy (neutering/spaying) were consistently associated with higher risks of OA across the entire study cohort and all 12 representative breeds evaluated.

• Weight Gain: Weight gain after maturity is a notable risk factor for OA. The study found that percent increases in body weight after desexing were associated with higher OA risks, particularly in larger dogs.

• Age at Desexing: There is an inverse relationship between age at desexing and OA risk. Dogs desexed at a younger age (<6 months) had a higher risk of developing OA compared to those desexed later (6-12 months, 12-24 months, and 24-60 months). This suggests that the protective effect of gonadal hormones regarding OA risk may be linked to skeletal development.

• Interaction Effects: The study noted a statistically significant interaction between desexing and adult weight, indicating that the increased risk of OA in larger dogs is more pronounced in those that have been desexed compared to intact dogs.

• Body Condition Score (BCS): While higher BCS was associated with OA, the effect sizes in the overall cohort were minimal, partly due to the challenge of standardizing BCS across different breeds and clinical practices.

Clinical Relevance

The authors suggest that these findings can assist vets in:

• Identifying High-Risk Dogs: Recognizing dogs at elevated risk early in life to implement appropriate preventative measures.

• Risk Management: Engaging in evidence-based discussions with owners regarding modifiable factors, such as weight management and the timing of gonadectomy, while weighing those factors against other health considerations.

• Proactive Surveillance: Triggering earlier diagnostic screenings and interventions for dogs identified with multiple risk factors.

One of our recommendations for monitoring dogs at risk of OA is to use the DogMA app. The Dog Mobility App is a tool used by caregivers to monitor their dog across their lifespan. This proactive approach encourages caregivers to play a role in their dog’s management and enhances engagement with vet professionals. 

Listen to our podcast

This approach fits with the recommendations from the COAST panel regarding education and awareness at various life stages.

Watch our webinar on OA guidelines

If you are keen on the detail of how the study was conducted, it’s listed here. 

This retrospective cohort study analyzed medical records from 131,140 dogs seen at Banfield Pet Hospitals in the United States between 1998 and 2019, specifically focusing on dogs with a death date in 2019.

• Data Source: Electronic medical records were extracted from the Banfield Pet Hospital network, which utilized a centralized proprietary system (PetWare®). The records included structured data (diagnoses, physical examination findings, services/medications) and unstructured narrative text.

• Inclusion Criteria: The study included dogs born after 1997 that were observed into maturity (2+ years) and had complete data for age at baseline and maximum body weight. Dogs with follow-up times exceeding 20 years were excluded.

• Variable Definitions:

  • Osteoarthritis (OA): Identified using specific structured diagnostic codes (e.g., "osteoarthritis," "arthritis," or "degenerative joint disease").

  • Body Condition Score (BCS): Standardized across different scales into a single 9-point scale.

  • Follow-up Time: Calculated as the interval between the first recorded visit and the date of OA diagnosis or death.

  • Wellness Plans: Treated as a stratifying variable to account for detection bias, as dogs on these plans had more frequent clinical visits and a higher likelihood of diagnosis.

Statistical Analysis

• Modeling: Cox proportional hazards models were employed to assess the relationship between OA incidence and various risk factors: age at baseline, sex, neuter status, age at neutering, and body condition metrics (weight and BCS).

• Breed-Specific Evaluation: To understand consistency across breeds, the same stratified Cox regression model was applied to 12 representative breeds, selected based on weight quartiles and sufficient sample size.

• Interactions: The researchers tested interactions between specific variables, such as desexing status and adult body weight/BCS, and percent changes in weight/BCS after desexing, to better understand how these factors modify OA risk.

Link to full text paper