Our Research Results on Ovaries and Longevity
Life course analysis of the impact of mammary cancer and pyometra on age-anchored life expectancy in female Rottweilers: Implications for envisioning ovary conservation as a strategy to promote healthy longevity in pet dogs. The Veterinary Journal 2017; 224(1):25-37.
Mammary cancer and pyometra are widely recognized as important, ovary-driven health hazards of pet dogs. Early ovariohysterectomy (spay) can reduce the incidence (occurrence) of these two diseases. In this manuscript, Dr. Waters reported results of the first-ever breed-specific, life course analysis of the impact of mammary cancer and pyometra on life expectancy and premature mortality in dogs. The analysis shows that at no time points during the life course was the current or future diagnosis of mammary cancer or pyometra associated with shortened survival compared to females who never developed these conditions.
Longevity in pet dogs: Understanding what’s missing. The Veterinary Journal 2014; 200(1):3-5.
In this invited editorial published in a top European veterinary journal, Dr. Waters urges us
to take a closer look at longevity research in dogs so we can gain an understanding
of what’s missing. It summarizes: Although the biology of successful aging is unquestionably
complex, solid progress in successful aging hinges on closer attention to two concepts:
life course perspective and whole organism thinking.
Caught in an act of convenience: Disentangling our thinking about the influence of ovariohysterectomy (spaying) on healthy longevity in dogs. In: Domestication History, Genetics, Behavior and Implications for Health. Nova Science Publishers Inc.; 2013; 115-120.
Ovaries are endocrine organs, not just reproductive units. When we remove endocrine organs,
we can expect to re-set the system, impact overall health. This essay uses accessible language
to describe how we might direct our re-thinking and shift the dialogue to illuminate
the longevity benefits of ovaries.
Exceptional longevity in female Rottweiler dogs is not encumbered by investment in reproduction. AGE 2013; 35(6):2503-2513.
This was the first study in the scientific literature to explore the potential trade-off between
investment in reproduction and longevity in dogs. In a detailed evaluation of reproductive
histories of Rottweilers that captured both reproductive intensity (number of offspring)
and tempo of reproductive effort (age at first and last reproduction), we found no evidence
that a bitch’s physiological investment in offspring is associated with disadvantaged
longevity. Instead, independent of reproductive investment, longer duration of ovary
exposure was significantly associated with highly successful aging.
In search of a strategic disturbance: Some thoughts on the timing of spaying. Clinical Theriogenology 2011; 3: 433-437.
The purpose of this paper was to provoke a thoughtful re-examination of our assumptions
regarding the health consequences of early, elective ovariohysterectomy in dogs. Ovaries
are endocrine organs so ovary removal is a physiological disturbance. This line of reasoning
raises a new set of questions. If we refocus our thinking on optimizing the timing of spaying
(rather than debating whether spaying is good or bad), can we make spaying a strategic physiological disturbance?
Probing the perils of dichotomous binning: how categorizing female dogs as spayed or intact can misinform our assumptions about the lifelong health consequences of ovariohysterectomy. Theriogenology 2011; 76:1496-1500.
Previous studies on spaying and longevity had categorized bitches as spayed or intact based on
gonad status at time of death. In this paper we showed this common method of categorizing
our study subjects – ignoring the timing of spaying in each bitch – distorts the real relationship
between number of years of ovary exposure and longevity. Our conclusion: Continuing to
categorize bitches based upon whether they are spayed or intact at time of death
is an inadequate method for representing important biological differences in lifetime
ovary exposure, which can lead to misleading assumptions about the overall health
consequences of ovariohysterectomy.
Exploring mechanisms of sex differences in longevity: Lifetime ovary exposure and exceptional longevity in dogs. Aging Cell 2009; 8: 752-55.
This study, published in the world’s top impact aging research journal, was the first to analyze
the relationship between the number of years of ovary exposure (age at spay) and likelihood
of exceptional longevity in dogs. Results showed that female Rottweilers were twice as likely
to reach exceptional longevity than male Rottweilers, but taking away ovaries during
the first 4 years of life completely erased the female longevity advantage. Evidence
from this landmark study, along with data from women and mice, point in the same direction:
Ovaries are part of a system that promotes longevity.
Exceptional longevity in pet dogs is accompanied by cancer resistance and delayed onset of major diseases. Journal of Gerontology: Biological Sciences 2003; 58: B1078-1084.
This report contained the first detailed description of pet dogs who had reached
exceptional longevity. Similar to human centenarians who live to be 100, oldest-old Rottweiler
dogs showed a delayed onset of major life-threatening diseases, including cancer. This paper
introduced the scientific community to pet dogs living in the same households as humans
as an attractive mammalian model of human aging to study the factors that regulate longevity
and cancer resistance.
Endogenous gonadal hormone exposure and bone sarcoma risk. Cancer Epidemiology Biomarkers Prevention 2002; 11:1434-1440.
This was the first study published in the scientific literature to focus on the role of sex hormones and bone cancer. Results showed that male and female Rottweilers who had their testes
or ovaries removed during the first 12 months of life had a 3 to 4-fold increased risk for bone sarcoma.