Aging: Dogs, Too, Can Hope to Live Longer

Geneticists at the University of Washington (United States) are studying the aging process in domestic animals*. According to them, certain common medications could help increase pets’ longevity, while also improving their health and quality of life. They have begun trials with rapamycin, an anti-rejection drug administered to transplant patients, to evaluate its ability to delay aging in dogs. This drug has already been shown to extend the lifespan of mice by more than 25 percent. A similar effect in dogs—which has yet to be confirmed—could extend their lifespan by several years. As human life expectancy continues to rise, the lifespan of pets, such as dogs and cats, seems far too short. However, research in the biology of aging has made major strides in recent years. In particular, molecules capable of slowing aging and extending lifespan have been successfully tested in small mammals, such as mice and rats. These same advances could benefit pets, such as dogs, which can now expect to live healthier lives and up to five additional years (two to three years for a large dog, four to five years for a small dog). Low doses of rapamycin, an immunosuppressant known to extend the lifespan of mammals, were added to the diet of 24 middle-aged dogs—Golden Retrievers, Labradors, and German Shepherds. The initial phase of this trial was intended solely to demonstrate the absence of significant treatment-related side effects. However, the researchers also observed statistically significant improvements in cardiac function in the dogs that received rapamycin compared to those treated with a placebo—similar to what had been observed in laboratory studies of aged mice. Of course, this is a study with a limited sample size, and the encouraging results need to be replicated on a larger scale and over a longer period of time. At this stage, there is no evidence that the improvements in cardiac function observed with rapamycin indicate a more general improvement in the dogs’ health, or slowed aging, nor is it known what the long-term side effects might be. Analysis of the data collected during this first phase is still ongoing, and the full results have not yet been published. Phase 2 of the trial is expected to begin by the end of the year and last three to five years. The dogs selected** for this study will receive a low dose of rapamycin and will be regularly evaluated through veterinary examinations and activities with their owners. Several age-related functions and characteristics will be monitored (cognition, cardiovascular and immune systems, and cancer incidence).  

Unexplained Differences in Longevity

Wild canids live longer than their domestic counterparts. However, some dogs have reached the remarkable age of 29 years, leading scientists to believe that these animals possess a metabolism capable of keeping them alive and healthy for longer than is currently the case. However, it remains difficult to determine why certain animal species live longer than others. For some, their longevity is thought to be due in part to the fact that they have faced few predators over millions of years. This would also explain why life expectancy tends to be higher among larger animals. Solitary species also live to a greater age, likely because they are less exposed to disease than if they lived in large populations. For a long time, it was believed that species with higher metabolic rates and faster heart rates lived shorter lives because of their faster biological clocks. However, some animals with rapid heart rates, such as parrots, do not seem to follow this rule. Macaws, for example, can live past 100 years. Trials conducted on dogs could also benefit humans. Many researchers are currently working to increase human life expectancy. One study, launched this year, aims to determine whether metformin, a drug used to treat diabetes, can increase longevity in humans. * For more information: http://dogagingproject.com/ ** To participate in Phase 2 of this trial, which includes dogs at least 6 years old, weighing at least 18 kg, and in good health: http://dogagingproject.com/phase-2-application/