Searching for the Origin of the Natural Lifespan of Havanese

The Havanese Club of America, Inc. (HCA) has been carefully monitoring the evolution of the health of the breed since its recognition in 1996. Indeed, four major health surveys have been conducted by the HCA’s Health Committee since then.1 The first two general surveys (2004 and 2012) contained over 2000 dogs. These early surveys showed that Havanese are a relatively healthy breed prone to very few genetic or early-life-threatening diseases. That they were a “long-lived” breed and endowed with many charming characteristics, has led to both their enormous popularity as companion dogs and, in more recent years, helped to propel them to the height of recognition in the show ring.

The third survey was conducted in 2017. Known as the “Longevity Survey,” it answered the question of how many years Havanese actually lived. The answer turned out to be quite surprising, but posed many additional questions! That survey included 512 mostly AKC registered Havanese, going out in age to almost 19 years. It showed that while the average
lifespan of both sexes was 13+/-0.5 years, those Havanese surviving beyond their 9th or 10th birthday had even longer average lifetimes—closer to 15 years. At first glance the reason was simple: If one looked at a plot of the lifetime of the Havanese reported in the survey, there wasn’t a simple peak at the average lifespan, but rather a “bulge” at about 9 to 10 years, and a larger peak to the right—at almost 15 years lifetime. The bulge contained almost 20% of the survey population and it effectively “dragged” the average lifetime down to 13 years. Thus, if that bulge were removed, the balance of the dogs would have had the much longer 15 year average lifespan. Unfortunately, the survey left unanswered what the cause(s) of this bulge of early mortalities was. Nor did it speak to what the ultimate cause(s) of death were.

In 2018, in response to this puzzle of early mortalities, a major follow up survey (the “Rainbow Bridge Survey”) was initiated. The goal was to try to uncover the principle causes of natural death, and catalog them as a function of age and sex. We could also examine whether spay/neuter age and lifestyle at all influenced lifespan or cause of death within the reported population. The Health Committee hoped to use this information to improve the existing health testing guidelines, and further increase lifetimes and the quality-of-life for
the breed.

Over a year and half, the Health Committee collected information on a total of 156 Havanese, largely from HCA and AKC breed club members. About a third of the responders were or had been Havanese breeders. Responders were asked to provide the dog’s sex, registration, age at death, cause of death, the basis for determining cause, as well as spay/neuter age and lifestyle. A comparable number of females and males were reported.2 The primary causes of death were then compiled into 12 major categories [e.g.: natural death/cause unknown, cardiovascular, cancer, liver, kidney, endocrine, neurologic, etc.], with more than 65 detailed subcategories. The assignment of primary cause was based solely on the information provided by the responder. Each dog was then independently assigned to these primary categories by both the author and a committee member and author who is a practicing veterinarian.3 Secondary and/or tertiary causes were compiled as well.

The survey confirmed that the lifetime distribution was not a simple peak, but as before, it exhibited a modest fraction of early mortalities. We could now, however, look deeper at the causes of death as a function of age and sex and, with this new information, a number of unexpected patterns began to emerge.

Perhaps not unexpected, the two most common health issues arising in the early mortalities were cancers and cardiovascular diseases (26% and 27% of the sample, respectively). Cancers resulted in shorter average lifetimes of 10.3 years, while cardiovascular disease lead to death at about 12.4 yrs. The types of cancer varied widely, but liver/spleen, b & t-cell lymphoma, and leukemia were the most prevalent. Most of the reported cardiovascular diseases appeared in midlife, but ultimately resulted in congestive heart failure.

These short average lifespans, and the distinct difference in lifespan for cancers and cardiovascular diseases, account for much of the distortion of the lifetime distribution for both males
and females.

The least expected finding was the observation that cancers occur much more frequently in the male population (37.5+/-8.5%) than in the females (17.9+/-5.0%) while cardiovascular diseases are more prevalent in the female population (35.7+/-7.6%) compared to the males (22.2+/-6.1%). While the sample was small, the observed difference between males and females for all cancer-related deaths has a 1 in 386 chance of being a statistical fluctuation. The difference for cardiovascular-related mortality rates between sexes has a 1 chance in 476 of being a fluctuation. And, while the rate of occurrence is different for females and males, there is no significant difference by sex in the corresponding lifespans for either of these two diseases.

The next smaller contributor to early mortalities are non-cancerous diseases of the liver, occurring at a much lower frequency (5.8+/-1.9%), but with no statistically significant difference between sexes. The average age at death is, however, quite low, 6.9+/-1.1 yrs. These are comprised largely of chronic liver disease and Hepatitis as opposed to Microvascular Disease or Portosystemic Vascular Disease—thought to be common in smaller
Toy breeds.4

Neurological diseases, the final large category leading to earlier deaths, make up 5.8+/-2.0% of the population. The average age at death is 10.8+/-1.6 years and is similar for both sexes. Neurologic diseases are, however, widely distributed in age, but there is a suggestion in the data of excesses in both the younger and the older dogs which correlate to the reported causes (e.g.: seizures in younger dogs and dementia in older dogs).

When we examined those dogs that survived to the oldest ages, we found that 9.6% of the total population died naturally of an unknown (undiagnosed) cause, and had an average lifetime of 14.7+/-0.4 yrs. A small fraction of all dogs (8.3%) were euthanized for quality-of-life issues (without an
underlying diagnosis being reported). Their average age was 15.3+/-0.3 yrs. In both these classes, the number of females and males in the sample were almost equal.5 Kidney disease/failure stood out as a leading diagnosed component of mortality in these older dogs, occurring in 9.6+/-2.5% of the population and leading to death (usually by euthanasia) at 14.2 +/-0.9 yrs. The disease appeared as well in an almost equal number of females
and males.

In all living animals, we expect there to be a natural progression of cellular degeneration, ultimately leading to death by the failure of one or more organs. This process is accelerated by diseases which lead to earlier degeneration in the functioning of one or more individual organs, followed by death. Accordingly, we can use the survey to answer the question, “What is the natural lifespan of Havanese?” One way to think about characterizing the natural lifespan is to define it by those dogs that died either of unknown cause or were euthanized for quality of life with no explicit underlying illness or died from a classic natural organ failure associated with old-age—such as kidney failure. These three “older-age” categories represent about 27% of the survey population and their average age at death allows us to define 15.1+/-0.4 years as a natural lifespan for Havanese.

 

In all living animals, we expect there to be a natural progression of cellular degeneration, ultimately leading to death by the failure of one or more organs.

Thus far, we have accounted for about 92.3% of the dogs in the survey. Dogs in all the other primary categories (dermatological, intestinal, endocrine, and miscellaneous diseases) had lifetimes that were distributed fairly uniformly (with an average of 11.5 years) and did not exhibit any statistically significant patterns
of mortality.

Finally, we tried to use the data that was collected for each dog to examine correlations with spay/neuter age and lifestyle. Spay/neuter age is strongly correlated to those dogs used in breeding—the two populations divide cleanly around two years of age. While no statistically discernible differences in their subsequent lifespans or cause of death were observed with spay/neuter age, there was intriguing evidence that the 24 dogs living in rural (versus 99 dogs in urban and suburban) environments had statistically significant longer average lifetimes (by almost 2.5 years). The latter observation, however, requires careful confirmation by a separate study with both higher statistics and more precise definitions of lifestyles—something that the Health Committee is considering for the future.

This article has been approved by the Board of Directors of the Havanese Club of America, Inc. An abbreviated version appears in the March 2021 AKC Gazette.

1 The complete reports from each of the four surveys are available on the “Health tab” at https://havanese.org/ under surveys.

2 There is no mechanism to know, independently, the extent that the sample population is totally unbiased, correctly representing the population at large. This uncertainty cannot, therefore, be included in the errors. Indeed, some categories may be under-represented (see footnote 5) making the true frequencies of occurrences of the other categories smaller in the general population. However, relative frequencies reported within each category, average ages, and differences by sex are less likely to be biased.

by Dr. Rafe H. Schindler

3 The Rainbow Bridge Survey report was authored by Sara D. Dellorto, Dr. Adam King, DVM, and Dr. Rafe H. Schindler.

4 A comparable number of liver cancers were observed. They resulted in later deaths at ~10 years, consistent with the typical cancer mortality age, and where they are specifically accounted.

5 It is plausible that these two categories are under-represented in the population. Not having a specific cause of death, for example, may have led respondents to not report their dogs in the survey. This is unlikely to affect the average age of these deaths—only its statistical uncertainty. However, as discussed in footnote 2, undercounting one or more categories leads to higher observed rates for the other categories in the survey.

  • Dr. Rafe H. Schindler is a professor of Elementary Particle and Particle Astrophysics at Stanford University. He has chaired the club’s Health Committee since 2015. Dr. Schindler and his spouse have bred and shown Havanese for more than 15 years and are Havanese Club of America Breeders of Distinction and American Kennel Club Breeders of Merit.

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