How Body Size and Head Shape Impact Behavioural Aging in Dogs – My “Best of Health” article for January 2024

♦ January 25, 2024

As dog breeders, we know that different breeds have vastly different life expectancies. Small breeds like Chihuahuas can live over 15 years, while giant breeds like Great Danes rarely make it past 7 or 8. This two-fold difference in lifespan likely translates to differences in how dogs age behaviourally and cognitively as well. But how exactly does expected lifespan impact dogs’ senior years? And what other physical traits, like body size and head shape, influence ageing patterns?

A new large-scale study by Turcsán and Kubinyi (2023) sheds light on these questions by analysing survey data from owners of over 15,000 pet dogs worldwide. Their findings reveal key insights into how morphological factors affect dogs’ behavioural healthspan and risk of cognitive decline. As breeders and owners, understanding these patterns can help us make informed breeding choices to improve our dogs’ quality of life into old age.

Body size matters most

Of all the factors studied, body size had the most consistent impact on ageing patterns. Dogs over 30 kg showed an earlier decline by 2-3 years in behaviours like trainability, motivation, playfulness, and cognitive functioning. However, their rate of decline was slower than smaller dogs. Giant breeds also had lower prevalence of canine cognitive dysfunction (CCD) risk by old age.

In contrast, small dogs showed more gradual behavioural decline starting later in life. But they had a much sharper downward trajectory and higher CCD risk by their senior years. Medium-sized dogs (9-30 kg) seemed to experience the most optimal ageing patterns. Their behavioural decline began around the same time as larger dogs but progressed more slowly into old age.

These findings contradict the idea that short-lived giant breeds simply experience accelerated ageing. It seems their early behavioural changes are more related to physical decline than cognitive decline. Breeders of giant breeds could, therefore, focus on improving structural soundness to help delay this physical breakdown. For breeders of small and medium breeds, maintaining cognitive health into old age should be made a priority.

Head shape influences CCD risk 

Skull shape also impacted ageing patterns, though less consistently than size. Dolichocephalic (long-headed) dogs showed earlier decline in trainability than mesocephalic or brachycephalic breeds, but later onset of cognitive changes. Most notably, they had double the CCD risk by old age compared to brachycephalic and mesocephalic breeds.

This indicates skull conformation affects vulnerability to cognitive decline. Breeders of dolichocephalic breeds like collies or borzois could prioritise early cognitive enrichment and lifelong training to help preserve mental faculties into old age. Meanwhile, breeding for moderation in skull morphology may help reduce CCD risk.

Purebreds face higher CCD threat

Purebred dogs showed no difference in onset or rate of behavioural decline compared to mixed breeds. However, they did have almost 1.5 times higher CCD prevalence by old age. This highlights the increased susceptibility of purebreds to neurodegenerative disorders due to genetic homogeneity. It seems that the hybrid vigour of mixed-breeds helps them maintain their cognitive health longer than is the case for purebreds.

As breeders, we play a key role in improving breed health through responsible breeding practices. Conducting genetic testing, being aware of the impact of closed gene pools, and introducing new bloodlines can help address this issue. We can also educate puppy buyers about providing extra cognitive enrichment to purebred dogs as they reach their senior years.

When do owners perceive “Old Age”? 

Surprisingly, most owners perceived their dogs as “old” by 6 years of age – long before major behavioural decline occurred. Only 20% of 6 year olds were considered old, but this sharply rose to 90% by age 12. Size and head shape impacted when this plateau was reached, but not the initial uptick around 6 years.

This reveals a disconnect between actual and perceived ageing patterns in dogs. As an influential source of breed information, breeders can help educate owners that while some greying and slowing down is normal by 6 years, most behavioural ageing occurs years later. This allows owners to support their dogs better for fuller, healthier lifespans.

Key takeaways for dog owners

1. Body size has a big impact on ageing. Giant breeds over 30kg experience earlier physical decline leading to behavioural changes as early as 5-6 years old. Small breeds show cognitive decline later around 10 years old. Aim for a medium 9-30kg dog for optimal healthspan.

2. Purebred dogs have a higher risk of cognitive dysfunction than mixed breeds. Be vigilant about cognitive symptoms like disorientation and provide plenty of training/games.

3. Long-headed (dolichocephalic) dogs like collies are more prone to cognitive decline than medium or short-headed dogs. Prioritise brain exercises and training especially as they reach senior years.

4. Most owners think their dog is “old” by 6 years, but major behavioural decline happens around 10 years. Don’t mistake some grey hairs for full “old age”. Keep providing exercise and enrichment for their brain and body well into the senior years.

5. Every dog ages differently based on breed, genetics, and care. Get to know your individual dog’s ageing patterns and adjust their care accordingly. Work closely with your vet for the best preventative care and early intervention.

6. Keep your dog’s environment and routine consistent as they age to reduce disorientation. Consider ramps, orthopaedic beds, and softer foods to accommodate physical limitations.

7. Engage in scent games, trick training, food puzzles etc. to maintain cognitive skills into old age. Always keep training sessions positive and low-stress for an ageing dog.

8. Monitor your senior dog for signs of cognitive decline like confusion, anxiety, forgetting commands, or house soiling. Report it to your vet as it can indicate neurological issues.

9. With proper care and prevention, dogs can live long lives with excellent quality of life. Be proactive about your dog’s healthcare and cognitive enrichment to help them thrive as a geriatric!

As experts on our chosen breeds, we have significant influence on both breeding practices and public perceptions. By applying these research findings, we can continue improving dogs’ healthspan and help owners better care for their ageing companions. Through responsible breeding for physical and cognitive soundness, we can ensure dogs of all shapes and sizes can live their senior years to the fullest.

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