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Reference Desk March 2012

Can Dogs Teach Us How to Live Long Lives?

by Mary Fuller, DVM

    Just think of all the things that dogs do for us. They can lower our blood pressure, chase away the blues, and make sure that we get our exercise.

    Now, according to a presentation by Dr. David J. Waters at the North American Veterinary Conference, dogs can also teach us a thing or two about growing older.

    As the director of the Center for Exceptional Longevity Studies at the Gerald P. Murphy Cancer Foundation, Dr. Waters works to determine if the secret to healthy aging can be unlocked by studying pet dogs with extraordinary longevity.

    Specifically, Dr. Waters and his colleagues are working to identify which genetic and environmental factors may add not just years—but healthy years—to a life.

    As a starting point, Dr. Waters focused on more than 140 of the oldest Rottweilers—those who were still going strong at 13 years of age, which is about the equivalent of 100 human years. While most Rottweilers typically reach 8 to 10 years of age, only about one in 6,000 Rottweilers in the United States makes it to the age of 13.

    Rottweiler

    Detailed information was collected from each dog to determine which factors contributed to their longevity. In 2010, when only 15 of the dogs were still alive, Dr. Waters embarked on “The Old Grey Muzzle Tour,” visiting each canine across 13 states to collect additional medical and lifestyle information.

    Of the 15 remaining “centenarian” dogs, females outnumbered males by 11 to four. Dr. Waters found a striking similarity in people: Women who lived to be 100 also outnumbered men—by a ratio of four to one. Why were females—both canine and human—more likely than males to reach this ripe old age?

    One possible explanation, according to Dr. Waters’ study, is that Rottweilers who kept their ovaries longer actually lived longer. And dogs who had their ovaries removed before four years of age were less likely to break longevity records.

    These findings paralleled the results of a recent Nurses’ Health Study of 2,900 women: Participants who had an elective hysterectomy but kept their ovaries had lower overall mortality than women who had both the uterus and ovaries removed.

    Even mice appear to gain an advantage from their ovaries. In another study, the ovaries from young mice were transplanted into older mice who'd previously had their ovaries removed. Guess what? The newly implanted ovaries in older mice actually extended their life expectancy.

    So does this mean that every dog will benefit from keeping her ovaries? Not necessarily, admits Dr. Waters.

    In addition to helping to reduce pet overpopulation, ovariohysterectomy (the removal of the uterus and the ovaries) still has many benefits. Dogs who are spayed early have a lower risk of developing mammary cancer. The procedure also eliminates the risk of developing pyometra, an often life-threatening infection of the uterus, as well as other sex hormone–related conditions.

    Still, these studies do suggest that choices made early in life can influence health in later years.

    Dr. Waters is also studying the relationship between aging and cancer, since cancer risks increase with age for both people and dogs.

    In one study, cancerous rat cells were implanted into the livers of both young and old rats. Within a week, all the rats had tumors. But, by day 85, all of the tumors had cleared from the young rats, while 90 percent of the older rats still had tumors.

    Could this mean that older bodies provide a better environment for cancer cells? If this is true, why is it that people who live to be 100 generally don’t succumb to lethal cancers?

    According to Dr. Waters, the same proved true for dogs in his study—the oldest dogs were rarely diagnosed with cancer. Could it be that the oldest dogs and people have more cancer-resistant genes than everyone else?

    The questions are certainly intriguing. And while Dr. Waters doesn’t have all of the answers yet, he’s hoping to prove one thing: Old dogs can teach us a few new tricks.

    Source: Vetstreet

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    Did you know... 51% of veterinarians reported a net decrease in patient visits over the last two years, while 42% said that revenues decreased in 2010 as compared to 2009. Read More

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