Possibly the most common question we receive is ‘Why aren’t you including small dogs in your project?’ The answer is, we are. And we aren’t. Every study has to have a focus, it has to have a goal that can be measured and compared with the funding available for that specific study. And we have a variety of trials, or studies, in the works.

The longitudinal study will include a variety of dogs, large and small, all over the world. The goal of this study is simple and far-reaching and will have a huge impact on the future of veterinary care. We will track a variety of health parameters over the entire length of a dog’s life. No drug interventions are part of this one, as the goal is to understand how and why some dogs get sick at a young age, while others live a long and healthy life. It will result in a huge database open to anyone. It will give veterinarians especially a more accurate picture of just what normal aging is in different breeds of dogs. We want at least 10,000 dogs involved in this study, for the clearest picture of what constitutes normal aging in dogs. If you haven’t enrolled in the longitudinal study, you may do so here.

We already know that big dogs tend to age faster than small dogs. The average lifespan of a Chihuahua is 12-20 years for example, while that of a Great Dane is 8-10 years. Why is that? Honestly, scientists don’t know exactly. It is at least partially due to higher levels of IGF-1 signaling in big dogs, which is the single greatest predictor of body size in dogs. Beyond that, there are many different theories being explored.

Our intervention trials with Rapamycin focus on large dogs over small ones because we want to know as soon as possible if rapamycin makes a difference. The math is a bit complicated, but the statisticians tell us that in order to be able to detect a 15% increase in lifespan from rapamycin, we need to study about 500 larger dogs for 5 years. It would take about twice as long, or we would need about twice as many dogs, to be able to demonstrate the same effect in small dogs, because they age more slowly. Another practical consideration is that the vast majority of NIH funding comes in the form of 5-year grants, so any study we propose to NIH has to be doable in that time frame. A rapamycin intervention trial on small dogs would be nearly impossible to get funded through NIH, which we view as our most likely source of funding.

It is important to realize however that what we learn from the intervention trials can be applied to all dogs. Except for some breed specific disorders, all dogs get old in pretty much the same way. All people get old too. The basic mechanisms are likely the same. What we learn for big dogs will apply to small ones as well.

Future intervention trials may very well include small dogs. The only thing holding us back is funding. Do you sense where I’m going with this? You guessed it. You could donate. All of Phase 2 has been funded by a private foundation. All of any particular trial can be tailored to donor wishes. We are not likely to turn away funding for a small dog intervention study. We just haven’t received one yet.


by Tammi Kaeberlein

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