Living with a dog can help humans in lots of ways, from reducing stress and anxiety to lifting our spirits and making us laugh. Yet despite the abundance of benefits dogs offer, they also come with a notable drawback: Their life spans are much shorter than ours, forcing us to deal with the sadness of their deaths every 15 years or so.
Grieving for our dogs is just part of life, and in the big picture, it's a small price to pay. But according to researchers at the University of Washington (UW), there may be a way to help our best friends stay with us — and stay healthy — a little longer.
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Dog aging varies widely by size and breed, with smaller dogs typically maturing more quickly, yet also living a few years longer on average. It's also common for mutts to outlive purebred dogs, thanks to the perks of higher genetic diversity. But while almost any dog is considered elderly by age 15, some have been known to nearly double their expected life spans — including Bluey, an Australian cattle dog who famously lived to see his 29th birthday last century.
And now researchers at UW's Dog Aging Project (DAP) are working to bring similar longevity to canines of all kinds. In addition to performing "the first nationwide, large-scale longitudinal study of aging in pet dogs," this project involves efforts to improve dogs' "healthy life span" via therapies that already work in lab settings.
"To be clear, our goal is to extend the period of life in which dogs are healthy, not prolong the already difficult older years," the project's website explains. "Imagine what you could do with an additional two to five years with your beloved pet in the prime of his or her life. This is within our reach today."
If it pans out, this may also aid ongoing research into extending the lives of other animals, including humans. But for now, the therapy is focused on dogs.
Namely, they're testing the FDA-approved drug rapamycin (aka sirolimus) on middle-aged dogs. High doses of rapamycin are already used in humans to fight cancer and prevent organ-transplant rejection, but at low doses, it has also been shown to slow aging and extend life span in several animals with few or no side effects. In mice, for example, the immunosuppressant can lengthen lives by up to 25 percent.
"If rapamycin has a similar effect in dogs — and it's important to keep in mind we don't know this yet — then a typical large dog could live 2 to 3 years longer, and a smaller dog might live 4 years longer," the project's organizers write. "More important than the extra years, however, is the improvement in overall health during aging that we expect rapamycin to provide."
Rapamycin trials have already begun on 32 middle-aged golden retrievers, Labrador retrievers and German shepherds. Ranging from 6 to 9 years old, these dogs will spend several months on a low-dose rapamycin regimen in which researchers study age-related metrics like heart function, immune response, physical activity, body weight and cognitive measures. They'll also follow these 32 dogs throughout the rest of their lives, looking for any significant changes in aging or life span.
And in phase two of the study, a second group of middle-aged dogs will enter a longer-term, low-dose rapamycin regimen "designed to optimize lifespan extension." Based on mouse studies conducted both at UW and elsewhere, they anticipate the drug "could increase healthy lifespan of middle-aged dogs by 2-5 years or more."
Rapamycin isn't a miracle drug, however, and high doses have been linked to side effects like immune suppression and delayed wound healing. But as the DAP website argues, "these are greatly mitigated at the doses used to extend longevity, and both animal and human studies indicate that even mild adverse events are rare."
While the idea of extending dogs' lives is exciting, it's important not to let quantity of life overshadow quality of life. We may never have full control over how long our dogs live, but we can make sure they live well while they're here.
A good reminder of this comes from Pegasus, a Great Dane rescued from unscrupulous breeders in South Africa when she was 4 weeks old. Suffering from a pigment deficiency often associated with blindness and deafness, Pegasus wasn't expected to live very long. Filmmaker Dave Meinert adopted her anyway, and decided to film her daily as she grew up. In May 2015, he released a time-lapse movie (see below) of her reaching adulthood that quickly went viral. And as he explains in the video, Pegasus' prognosis only helped the pair live every day like it was their last.
"I still don't know how long she is going to live," Meinert admits. "But right now is pretty great."