Photo courtesy of Center for Exceptional Longevity Studies/Gerald P. Murphy Cancer Foundation
Kyrie, a 15-year-old female Rottweiler from Homer, Alaska, was the first dog to be visited by Dr. Waters during The Old Grey Muzzle Tour 2013.
Cancer - a disease in which cells go mad systematically - is often associated with aging. Figure out something intrinsic to aging, and we may end up unlocking new information on cancer that can help save canine, feline, and human lives. More specifically, if we can understand why some dogs of a cancer-prone breed manage to live far beyond their expected lifespan, we may not have to find ways to treat it. Maybe we can prevent it instead.
A research veterinarian with a background in oncology and aging crossed the country earlier this year to visit Rottweilers in their homes to try to understand why some dogs age better than others. Some of that information will pertain to people, too. David J. Waters, PhD, DVM, hit the road March 1 in Homer, Alaska, for his second Old Grey Muzzle Tour. In addition to being a professor of oncology at Purdue's vet school, Dr. Waters is the director of the Center for Exceptional Longevity Studies at The Gerald P. Murphy Cancer Foundation in Indiana. He has established the first database to track long-lived Rottweilers in order to study the factors involving successful aging.
Waters sees a connection between longevity and lack of active cancer. He thinks we don't pay enough attention to preventing cancer as opposed to treating it. Something happens in old tissue that can cause cancer to set up housekeeping, and Waters wants to know what it is.
Waters believes that in exceptionally long-lived dogs and people there is a resistance to dying of cancer. He thinks that if we know what the resistance is, we can learn to duplicate it.
He studies aging and longevity in Rottweilers because they are so prone to cancer. Rotties have an average lifespan of 8 to 9 years; cancer causes about 80% of those deaths at that age. If a Rottie lives to be 13 - the equivalent of a person living to 100 – cancer mortality drops to only 25%. In people, the risk of cancer in 100-year olds is only 4%.
While relatively few of these dogs die of cancer, Waters’ autopsy studies show that more than 90 percent of them actually have one or more types of cancer at the time of death.
"These Rotties have figured out how to treat cancer like an annoyance, like athlete's foot," Dr. Waters said at his stop at Veterinary Village in Lomira, Wisc. "They have cancer, but they can hold it at bay."
In his research, he's evaluating the impact of early life choices and interventions on healthy longevity - as opposed to frail longevity - and learning a bit about how factors such as stress and ovaries affect aging. He’s creating a frailty index for dogs.
In terms of stress, his hypothesis is that highly successful aging may be related to cortisol levels.
"If you don't handle stress well, your cortisol levels stay up," Waters said. "It does bad things. It's not healthy. With aging in dogs and people, cortisol levels go up. The better you handle stress, the healthier you will be. There is plasticity to longevity."
Measuring serum cortisol levels is one way to measure stress, so those levels were evaluated in the geriatric dogs. The exciting results: None of the old dogs he's encountered over the years had elevated cortisol levels. Instead, 40% of them had low cortisol levels, but retained a youthful response to a challenge. Waters points out that the knee-jerk medical response to the basal cortisol results is "it makes sense they might be low, the dog is ancient," but he thinks there is more to it than that.
Of course, without cortisol tests taken when young, it's impossible to know if the dogs always had low cortisol. Before this research, no one thought to ask whether highly successfully aging individuals might be able to side-step the aging-associated increase in stress hormone levels.
One thing he has discovered while traipsing about the country is that these old dogs are not reactive to most things. Instead of being afraid of nail clipping or vacuum cleaners, these dogs are generally nonreactive. He hears such things as "well, he doesn't like hot air balloons” to describe temperaments.
"Our research results urge fresh thinking: High stress hormone levels are not an obligate part of aging," he said.
The impact of ovaries makes a difference, in his opinion. He was taught to remove the ovaries early to lessen the risk of mammary gland cancer, but he has learned from studying Rottweilers that if they are removed early it erases the female longevity advantage. A paper published by Waters’ team has shown the longevity benefits of ovaries are independent of reproduction. He says there are published papers, including one of his, on why dogs should keep their ovaries: because ovaries are part of a system that promotes longevity. Human research is coming to similar conclusions for women.
"Why would you make lifestyle choices, such as keeping ovaries, based on avoiding one disease, mammary cancer?" he asked. “We need to consider potential trade-offs and the impact of our decisions on overall healthy longevity from a more holistic perspective.”
However, this news doesn't mean that you must keep your female intact to reap the benefits of keeping ovaries longer. During a spay, a dog's ovaries don't have to be removed, although traditionally they have been. Your veterinarian can remove the uterus and leave the ovaries, a procedure sometimes called a partial spay or ovary-conserving hysterectomy. It still eliminates the ability to get pregnant, bleeding and heats, and the risk of pyometra as long as all of the uterus is removed.
Waters is seeking the key to healthy longevity and how these lovely old Rottweilers manage to become old Rottweilers. His long-term goal is to find out how people and pets can view cancer as an annoyance rather than a killer. He may do it in his lifetime and he may not, but he's asking new questions - and that's what produces new results.
If you have a Rottweiler aged 13 or over, you can contact Waters’s research team at http://www.gpmcf.org/index.html, email@example.com, (765) 775-1005.
Timothy H. Tobish
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VIN News Service commentaries are opinion pieces presenting insights, personal experiences and/or perspectives on topical issues by members of the veterinary community. To submit a commentary for consideration, email firstname.lastname@example.org.