November 4, 2025, 9:38 am | Read time: 4 minutes
How much frailty in old age can shorten life apparently depends on how long a dog’s hormonal balance remains intact. A study of exceptionally long-lived Rottweilers shows: In males that were neutered early, the risk of death increased significantly with increasing frailty. While in those neutered late or not at all, this correlation disappeared entirely. This raises new questions about optimal neutering practices.
Can the Age-Related Decline in Dogs Be Halted?
Rottweilers typically have a life expectancy of eight to ten years. The study uses data from the “Exceptional Aging in Rottweilers Study” (EARS), a unique long-term project in North America focused on particularly long-lived Rottweilers (over 13 years). The goal was to determine which factors might be crucial for Rottweilers (and other dogs) to live particularly long lives.
Research on frailty in old age usually focuses on how to slow down age-related decline. It is much less common to investigate whether and how certain biological factors can mitigate the effects of frailty, contributing to so-called frailty resilience.
This is where the research team led by David J. Waters from the Gerald P. Murphy Cancer Foundation Center for Exceptional Longevity Studies (USA), in collaboration with Purdue University, comes in. The remarkable study was published in the journal Scientific Reports (2025). The scientists examined whether the duration a long-lived Rottweiler remained unneutered had an impact.
Are Unneutered Males Less Frail?
The researchers analyzed 87 male Rottweilers aged at least 13 years. All animals were assessed using a validated, 34-point clinical frailty index (EARS-FI). They were then observed until their natural death. The dogs varied greatly in the duration of their “intact” HPG system—depending on when (or if) they were neutered.
If the dogs had a long-intact “hypothalamic-pituitary-gonadal (HPG) system”—a functional hormonal axis that, among other things, regulates testosterone—the negative effects of age-related frailty in males were influenced.
A similar correlation between low testosterone levels and higher frailty has already been researched in humans. The hormonal balance is regulated via the HPG axis. An early disruption—such as through neutering—can therefore potentially have long-term health effects.
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Intact Rottweilers Had a Protective Effect According to the Study
The results clearly show that the risk of mortality due to frailty strongly depends on the hormonal life course. In the entire group, the risk of death tended to increase with a rising frailty index.
The most affected were dogs with less than 2 years of an intact HPG axis: Their risk of death increased by 16 percent. In a second group, which remained unneutered for 2 to 9.8 years, the risk was only slightly increased. And in the group with more than 9.8 years of an intact HPG axis, there was no longer a significant correlation between frailty and mortality.
This protective effect persisted even when factors such as body condition, birth year, or reason for neutering were considered. An interaction analysis revealed: Each additional year with an intact HPG axis reduced the frailty-associated risk of death by about one percent.
Neutering Must Be Reconsidered in Veterinary Medicine
The study provides compelling evidence that a longer intact HPG system can significantly mitigate the health consequences of age-related frailty—at least in males. Whether a similar correlation exists in females requires further study.
While the influence of hormones on the development of frailty has mostly been studied, this work highlights a new aspect: the role of the hormonal axis in resilience against already existing frailty. The results suggest that early neutering—thus the early interruption of the hormonal axis—could impair the ability for resilience in old age in the long term.
The authors propose considering the integrity of the HPG system more as a potential biological regulator for frailty resilience in the future. And possibly also in terms of aging research in humans. A life-course-oriented perspective, as used in this study, seems particularly promising.
However, it must be emphasized that the assessment of body condition was carried out by the owners themselves and not by veterinarians. This could have led to misjudgments. Additionally, it remains unclear whether certain time windows for the protective effect of the hormonal axis are particularly crucial—a question that future studies with larger samples need to address. 1