Teaching Old Dogs New Tricks

Healthy Aging

Our Aging Companions

If only the dog’s gene of unconditional love was linked to longevity – then we could enjoy their warm snuggles and affectionate licks longer. Perhaps there is hope. Recently, the news covered Spike, a chihuahua mix who lived an impressive 23 years – and now, Bobi (a Rafeiro do Alentejo), who is over 30 years old!

In the Annual Review of Animal Biosciences, Ruple et al. wrote a nice review on the science behind dogs and aging, including how human advances are helping dogs live longer – and a few tricks they may be able to teach us humans about living longer, too.

Amazing diversity in one small word: dog

As shared by Ruple et al., dogs are an amazingly diverse species. From weighing less than 8 to more than 80 pounds, it is incredible to think that a toy poodle and great dane are the same species. What comes with different sizes, however, are different length lifespans. The smaller the dog, the longer it tends to live. This is no trivial matter – smaller dogs can live 2 to 3 times longer than the biggest dogs.

How dogs age

Dogs age similarly to us, and just like us, older dogs typically develop chronic diseases of aging. Older dogs can get arthritis, cancer, and Alzheimer’s disease (also called Canine Cognitive Dysfunction Syndrome). Lopez-Otin et al. have shown that our underlying drivers of aging are shared, too. This includes shortened telomeres, dysfunctioning mitochondria, and other key hallmarks of aging that are observed across many species, including humans and dogs. Over time, these cell-based changes with aging translate into our slowing, graying (but still sweet) dogs.

So, why does size matter?

According to Kraus et al., larger dogs simply age at a faster rate than smaller dogs. This is evident by similar aging-related breakdown processes, including physical disease onset, that occur across all dog sizes. As explained by Ruple et al., this phenomenon falls under the Compression Hypothesis, where a dog’s size directly dictates its aging rate. Interestingly, Sutter et al. showed that a single mutation in the insulin/insulin-like growth factor (IGF1) gene is a major determinant of small size in dogs – the same gene that has been associated with lifespan. So, it may just be that this mutation drives not only small size in dogs, but slower aging rates, too.

Now, about old dogs & new tricks

While the Compression Hypothesis holds true for physical aging-associated conditions, it does not translate to cognitive decline in dogs. As explained by Watowich et al., under the Truncation Hypothesis, dogs have to live enough years to develop cognitive decline. Shorter-lived large dogs don’t tend to develop Canine Cognitive Dysfunction Syndrome (CCDS) because they don’t live long enough for these changes to happen. In contrast, many small dogs develop CCDS due to their longer lives.

Here’s the good news for our little pals: lifelong training can protect them from developing CCDS. That’s right – continuing to teach your old dog new tricks can keep their brains younger and healthier, longer. Just like us humans and crossword puzzles.