In 2008, Waters offered a look at findings from the first 100 senior Rotts in the database in a presentation he called “Sex, Ovaries, Rock & Roll.” According to Waters, the results support the notion that how long females keep their ovaries influences how long they live.
Waters’ team found that Rottweilers spayed after age six were 4.6 times as likely to reach 13 years of age as those spayed at a younger age. Female Rottweilers normally live longer than males, a statistical norm also documented in humans. But according to Waters’ study, published in the journal Aging Cell (Dec. 2009 8(6):752–55), removing ovaries during the first four years of life erased the survival advantage.
Waters’ team spent a decade collecting and analyzing medical histories, longevity and causes of death for 119 Rottweilers in the U.S. and Canada, comparing them with a group of 186 Rottweilers with typical longevity. They found that female Rottweilers who kept their ovaries for at least six years were four times more likely to reach exceptional longevity compared to females who had the shortest lifetime-ovary exposure.
The findings mirror those of a human study, the Nurses’ Health Study, conducted by William Parker, MD, and colleagues from the John Wayne Cancer Institute in Santa Monica, Calif. This study, which included more than 29,000 women who underwent a hysterectomy for benign uterine disease, found that the benefits of ovary removal—protection against ovarian, uterine and breast cancer—were outweighed by a higher mortality rate from other causes. Parker pointed out that for 35 years, doctors have advised women undergoing hysterectomy to have their ovaries removed to prevent ovarian cancer. According to new findings, women who retain their ovaries for at least 50 years often live longer than those who don’t.
For dogs, the comparable age for keeping the ovaries intact, at least for large breeds like Rottweilers, is about six or seven years. (On average, Waters says, the 11 females he visited on his tour had “four years of lifetime ovary exposure.”) How ovaries affect longevity in Rottweilers is not understood, but many vets agree that hormones and genetic controls play a role in cancer.
However controversial, current research gives rise to a new set of questions. Waters compares sterilization to an ecosystem. Remove an element—say, caterpillars—and there are likely to be unanticipated consequences. A shorter lifespan might be one consequence of removing ovaries.
Nonetheless, Waters doesn’t recommend that people delay spaying their pets, saying that more research is needed. Not every Rottweiler benefits from keeping her ovaries. The challenge now is to identify which dogs will.
The research points to three options for owners of female dogs: do not spay; spay the dog after age six; or spay before puberty, which is the commonly accepted practice, and the one most vets recommend. In fact, spaying prevents two potentially fatal health problems: mammary tumors and pyometra, a serious uterine infection. It also helps with behavioral problems related to the heat cycle. And, of course, spaying helps curb overpopulation.
Waters’ work is part of a shift towards the study of healthy aging, which is more than simply long life. To that end, Waters, who is also professor and associate director of Purdue University’s Center on Aging and the Life Course, developed the first gerontology training program for vets, which teaches them how to educate owners on lifestyle choices.
Those of us who love pets can take heart: a dog’s environment and emotions; their diet; and, yes, their lifestyle, matter greatly. How we care for our dogs can make a huge difference in the quality and length of their lives. For example, studies show that slightly underweight dogs live an average of two years longer than heavier ones. Other studies have shown that the stress hormone cortisol plays a role in triggering the growth of later-stage cancer cells. Reducing stress by addressing behavioral problems could lower the probability of cancer in some dogs.