That one year of dog is seven human years? Well, that depends

The difference between the life expectancy of dogs and human life expectancy often involves emotional drama: we know that our companions are called to die long before us, that one day we will have to say goodbye to them and that, in that chain of dogs that becomes the biography of so many people, only one of those animals, the last one, will survive us. The close bond that leads us to share our lives cannot prevent biology from advancing at a very different rate in each species. Scientists have found in that lag an exciting object of study, since the aging of dogs becomes an accelerated version of ours: Investigating it, we can not only extend the existence of our furry companions (and, with it, delay that hard moment of goodbye), but perhaps also reach valid conclusions to slow down our own deterioration.

Interestingly, in this matter of the ages of the dog, We are governed many times by clichés, and the greatest of all is the one that equates a canine year with seven human years. This arithmetic tool so handy and with so much tradition (it is already mentioned in writings of the thirteenth century) is, of course, the result of comparing how long a dog usually lasts with what a person usually lasts, but its deficiencies are obvious without necessity to give them a lot of laps. The most obvious is that there are big differences between the life expectancy of the different dog breeds: the largest live, on average, less than ten years, while some of the smallest can approach twenty. Another obvious mismatch is that puppies reach sexual maturity in their first year, a trait totally alien to the 7-year-old boy or girl who is supposed to be equated with them.

A team from the University of California has examined the DNA of a hundred Labrador retrievers to refine that correspondence. Looking at methylation (an important part of epigenetics, that is, environmental factors that influence the expression of genes), they have established a more accurate graph of the dog’s ages: thus, the cheerful 2-year-old puppy would actually be equivalent to a 42-year-old adult, but from then on his aging slows down progressively, so that the 5 canine years would correspond to 56 humans and the 10 would come to around 68. The marked initial curve of the Labradors would be an accentuated version of the tables that already existed for medium dogs, according to which the first year of the puppy would be fifteen human years, the second would add nine and, from there, each would add five more.

Arthritis and obesity

This research has confirmed that both species experience similar molecular changes at different stages of life. It thus supports the studies that observe canine aging as a valid model of ours, among which it stands out the Dog Aging Project, a large-scale US initiative with 80,000 registered dogs. The owners of all of them have to fill in statistics and provide veterinary reports, but in addition the DNA of 10,000 of the specimens will be sequenced and biological samples of 1,500 will be taken. ‘Most of what we know about the biology of aging comes from studies done in yeast, worms, fruit flies and laboratory mice. The lives of these organisms take days, weeks or months in the carefully controlled environment of laboratories, ”explain those responsible. Faced with these aseptic conditions, so far removed from ‘real life’, dogs “share the daily environment of their owners, including climate variations, exposure to toxins and infectious diseases, meal times and exercise regimen”, in addition to having “a sophisticated health system” of veterinary consultations and clinics.

In fact, one of the studies behind the Dog Aging Project showed that dogs and people Not only do we share the most common chronic conditions (arthritis, obesity, diabetes, hypothyroidism …), but many of the main causes of death have a similar incidence at different stages of our lives. The greatest discrepancy occurs in deaths from cardiovascular diseases, much more frequent in humans, but the other seven most frequent reasons for death show a clear correlation by age. The evolution of deaths from cancer, for example, is almost identical, and there are even coincidences that deaths by accident are more common among young adults. Scientists trust that their first objective, to extend the existence of dogs, will later be transferable to humans, but they know that, in reality, with that first goal they would have already managed to improve the quality of our life: «We would give people more years with each dog.