Theriogenology
Volume 76, Issue 8 , Pages 1496-1500, November 2011
D.J. Waters, S.S. Kengeri, A.H. Maras, E.C. Chiang
Affiliations: Gerald P. Murphy Cancer Foundation, West Lafayette, Indiana
How categorizing female dogs as spayed or intact can misinform our assumptions about the lifelong health consequences of ovariohysterectomy.
In 2009, we reported findings from the first study evaluating the relationship between canine longevity and number of years of lifetime ovary exposure. All previous studies examining gonadal influences on canine longevity relied upon categorizing females as “intact” or “spayed” based on gonadal status at the time of death. Our study of Rottweilers generated a novel result: Keeping ovaries longer was associated with living longer. This result challenged previous assumptions that spayed females live longer. In the present investigation, we explored a methodological explanation for the apparent contradiction between our results and those of others, so we might better understand the impact that timing of spaying has on longevity. We hypothesized that naming female dogs as “spayed” or “intact” based upon gonadal status at time of death – a method we refer to as dichotomous binning – inadequately represents important biological differences in lifetime ovary exposure among bitches spayed at different ages. This hypothesis predicts that a strong relationship between years of lifetime ovary exposure and longevity in a population could be obscured by categorizing females as spayed or intact. Herein, we provide support for this hypothesis by reanalyzing longevity data from 183 female Rottweilers. In this study population, there was a three-fold increased likelihood of exceptional longevity (living ≥13 yr) associated with the longest duration of ovary exposure. However, categorizing females in this population as spayed or intact yielded the spurious, contradictory assertion that spayed females (presumed to have the least ovary exposure) are more likely to reach exceptional longevity than those that are intact. Thus, by ignoring the timing of spaying in each bitch, the inference from these data was distorted. It follows from this new understanding that dichotomous binning—naming females as spayed or intact—is inadequate for representing lifetime ovary exposure, introducing misclassification bias that can generate misleading assumptions regarding the lifelong health consequences of ovariohysterectomy.
Translation: The longer a bitch retains her ovaries, the better the odds of a longer life.
I found this interesting, especially as I am currently writing an article assembling documentation on the pros and cons of early canine castration for our quarterly magazine.
However, as I like to quote my sources, I'm a bit stumped by the date "November 2011" at the top. Did you have a sneak preview, or...? Many thanks.
I receive the table of contents and abstracts of articles "in press" for each issue of the magazine. You can sign up to get this by email on the magazine website. Full text of articles can also be ordered online for $15. http://www.theriojournal.com/
