'Oldest-Old' Rottweilers Continue to Advance Research on Healthy Longevity
Exceptionally long-lived Rottweilers — those that live to be 13 years of age and older — are providing important clues about successful aging. These "oldest-old" Rottweilers have lived at least 30 percent longer than the average for their breed.
"These exceptional dogs have dodged cancer and other life-threatening diseases of aging. We believe studying them can shed light on what it takes to live well," says David J. Waters, D.V.M., Ph.D., DACVS, director of the Center for Exceptional Longevity Studies at the Gerald P. Murphy Cancer Foundation located in the Purdue Research Park in West Lafayette, Ind.
The goal of learning more about this special group of Rottweilers — the equivalent of 100-year-old people — inspired Waters to visit them in their homes, where he could observe firsthand their environment and learn from their owners about what makes them tick. Waters set out on his famous "The Old Grey Muzzle Tour" in March 2010 to visit 15 of the longest-lived Rottweilers in the country.
Even before the tour, Waters and his research team had been collecting lifetime medical histories of the oldest-living Rottweilers. Established in 2007, the Exceptional Longevity Database was created to provide extensive data to aid research on successful aging in pet dogs. The database now contains information on more than 230 Rottweilers from 41 states and several Canadian provinces.
The Rottweiler Health Foundation awarded Waters a five-year grant in 2007 to support his cancer and longevity research in the breed. Additionally, the American Rottweiler Club has helped the researchers identify dogs to include in the studies.
Among the early findings from the research was that the likelihood of dogs dying from cancer rose with age during adulthood until dogs turned 10 years old, and then the risk began to decline. Exceptionally long-lived Rottweilers were less likely to die of cancer than were individuals with usual longevity. The findings led Waters to compare the oldest dogs to those with usual longevity in hopes of identifying genetic and lifestyle factors responsible for cancer resistance and exceptional longevity.
As more is learned about the biology of aging, Waters and his team hope to develop effective interventions that can interrupt disease processes in the early stages and therefore benefit overall health. An additional payoff is that the oldest-old Rottweilers may help contribute information relevant to healthy human aging.
Cancer has long been recognized as a disease of aging. Advancements in husbandry and medical care have contributed to dogs living longer and thus to cancer becoming more common. Both dogs and people have a high lifetime risk for cancer.
Waters, who is cross-trained in both aging and cancer, studies naturally occurring cancer in humans and animals and is finding that pet dogs present a novel approach to battling cancer. The compressed canine lifetime allows scientists to evaluate new prevention strategies and cancer therapies much faster than in humans.
Cancer similarities between dogs and humans are noteworthy. For example, dogs and humans are the only species that frequently develop prostate cancer, and the mammary cancer affecting dogs spreads to bones, just as in women. Osteosarcoma, the most frequent bone cancer in Rottweilers and other large breeds, has many similarities to the deadly osteosarcomas that affect teenagers.
"We see dogs as powerful tools to deepen our understanding of the aging process and the aging-cancer connection," Waters says. "New tools mean new hope — hope that the new research can lead to longer, healthier lives for both pets and people."
While the Exceptional Longevity Database provides scientists with a rich source of medical record information, the Biorepository at the Murphy Cancer Foundation serves as a source of serum, blood cells and DNA from the longest-lived Rottweilers. The banked samples are being used to help identify biomarkers — molecules in the blood, body fluids or tissues that signal a normal or abnormal process — to help measure signs of cancer, cancer resistance and aging.
To better understand cancer resistance, Waters' team has placed high priority on careful post-mortem evaluation of the vital organs of these exceptionally long-lived dogs. Waters believes these autopsy studies can help to determine whether cancer resistance reflects a complete suppression of the biological events that cause cancer. Through an increased understanding of cancer resistance, scientists will better position themselves to develop interventions that will reduce cancer risk.
The Effect of Spaying on Longevity
An important discovery from Waters' research on longevity was that female Rottweilers are two times as likely to achieve exceptional longevity as males. The research also uncovered a previously overlooked association: The longer females kept their ovaries, the longer they lived.
"If females retained their ovaries for more than four years, the likelihood of exceptional longevity increased to more than three times that of males," Waters says. "But taking away the ovaries during the first four years of life completely erased the female survival advantage."
The discovery came when the researchers studied 119 of the oldest-old Rottweilers in North America, of which the females had elective ovariohysterectomies performed at various ages. These "centenarian" Rottweilers were compared to a group of 186 Rottweilers with usual longevity of about 9 years of age. The data included the dogs' medical histories and their ages and causes of death. Telephone interviews were conducted with owners and veterinarians.
Waters' team was the first to evaluate whether the number of years of lifetime ovary exposure is significantly associated with exceptional longevity. "We observed a robust association between the length of lifetime ovary exposure and longevity that was independent of the cause of death," Waters says.
The research was published in December 2009 in Aging Cell.¹ The Rottweiler findings mirrored those reported in 2009 by Dr. William Parker of the John Wayne Cancer Institute when he evaluated 29,000 women who underwent a hysterectomy for benign uterine disease and showed that the positive effects of ovary removal were outweighed by increased mortality from other causes. The study, published in Obstetrics and Gynecology, showed that longevity was cut short in women who lost their ovaries before age 50.
The results from dogs and women indicate that ovaries are part of a system that promotes longevity. The findings provide strong rationale for future studies in both species to define the ovary-sensitive biological processes that promote healthy longevity.
More Research Is Needed
Scientists are seeking new animal models that more closely mimic human aging and foster new experimental approaches that will help find the factors that favor healthy longevity. The longevity research in Rottweilers has stimulated interest in the scientific community that pet dogs may become one of biogerontology's new workhorses.
The National Academies of Sciences invited Waters to write about the opportunities and challenges of dog aging research in The ILAR Journal in February 2011,² in a special issue devoted to benchmarking the most useful animal models of human aging. Waters wrote about the promises of studying exceptionally long-lived Rottweilers and relating the findings to aging in humans.
In November 2011, Theriogenology³ published an article by Waters in which he explored the methods that previous investigators had used to study spaying and longevity. It presented fresh thinking on how future studies on spaying and longevity might generate more reliable results.
"It's no longer a matter of judging whether spaying is good or bad, but rather a matter of estimating the timing of spaying that will benefit each dog the most," Waters wrote. In summarizing the article's message, Waters says, "Naming female dogs as spayed or intact based on their gonadal status at the time of death inadequately represents important biological differences in lifetime ovary exposure among bitches spayed at different ages. By ignoring the timing of spaying in each bitch, we introduce a misclassification bias that I suspect has generated some misleading assumptions about the lifetime health consequences of ovariohysterectomy."
An urge for a more careful focus on the impact that the timing of spaying has on the health of female dogs was published last December in Clinical Theriogenology.† Waters challenged veterinarians to reevaluate the health consequences of elective spaying in pet dogs and to recognize spaying as a physiological disturbance.
"If you remove the gonads, you reset the system in ways that could affect a diverse collection of outcomes ranging from the incidence of diseases to the way an individual responds to an immune challenge," wrote Waters. "By shifting the debate away from 'Should we spay or should we not?' toward a new question 'What age of spaying best promotes healthy longevity?', we prepare for making spaying a strategic disturbance." Prior to Waters' research of the oldest-old Rottweilers, no one had evaluated the association between longevity and the number of years of ovary exposure. The new research is leading to a greater appreciation for a life-course perspective of aging emphasizing that adult health outcomes can be profoundly influenced by things that occur in early life.
"While genetics typically claims 30 percent of the blame for why we don't live as long as the next guy, up to 70 percent revolves around lifestyle decisions," Waters says. "The choices owners make for their dogs may meaningfully contribute to longevity — whether it is diet, vaccinations, to spay or neuter, or even exposure to lawn chemicals. Ultimately, we want to get at the root of highly successful aging."
Purina appreciates the support of the American Rottweiler Club and particularly Elaine Starry, ARC health coordinator, in helping to identify topics for the Purina Pro Club Rottweiler Update newsletter.
¹ Waters DJ, Kengeri SS, Clever B, Booth JA, Maras AH, Schlittler DL, Hayek MG. Aging Cell. 2009;8:752-755.
² Waters DJ. The ILAR Journal. 2011; 52(1):97-105.
³ Waters DJ, Kengeri SS, Maras AH, Chiang EC. Theriogenology. 2011;76(8):1,496-1,500.
† Waters DJ. Clinical Theriogenology. 2011;3: 433-437.