How long will my dog live? Longevity Study – my October 2018 “Best of Health” article

Best of HealthHow long will my dog live?

It seems a long time ago, but in 2014 the KC ran its pedigree dogs breed health survey with an online survey that attracted just under 50,000 responses. Among these were 5663 reports of dogs that had died. Now, that set of mortality data has been analysed and published in an Open Access paper: “Longevity and mortality in Kennel Club registered dog breeds in the UK in 2014”. The co-authors are Tom Lewis, Bonnie Wiles, Aimee Llewellyn-Zaidi, Katy Evans and Dan O’Neill; names that will be familiar to many readers.

There are some interesting findings in the paper and I’d like to share a few of those, this month.

The most commonly reported causes of death were old age (13.8%), unspecified cancer (8.7%) and heart failure (4.9%); with 5.1% of deaths reported as unknown cause. Overall median age at death was 10.33 years. Breeds varied widely in median longevity overall from the West Highland Terrier (12.71 years) to the Dobermann Pinscher (7.67 years). There was also wide variation in the prevalence of some common causes of death among breeds, and in median longevity across the causes of death.

What do dogs die of?

All dogs are going to die of something (!) so it’s perhaps good news to find that owners reported “old age” as the most common cause of death. Interestingly, “old age” as reported by the owners ranged from just under 6 years old to just over 22 years old. The median age of death under the “old age”category was 13.7 years.

At the recent Breed Health Coordinator Symposium, Dr Mike Starkey told us that 1 in 4 dogs will be affected by cancer so it’s probably not surprising to see Cancer (of unspecified types) as the second highest cause of death. The median age of cancer deaths was just over 10 years, again suggesting it is as most people would expect, a condition of older age. The range for age of death due to cancers was very wide: 2 months to 21 years.

What do different breeds die of?

It’s well-known that canine longevity varies considerably depending on the size of the breed; giant breeds have shorter lifespans while smaller breeds tend to live longer. Of particular interest to me was a previous VetCompass study that showed Miniature Dachshunds to be among the longest-lived breeds. This breed was subsequently chosen to be a long-lived representative in a genome-wide association study that Cathryn Mellersh (AHT) and other colleagues conducted to compare the genomes of long and short-lived breeds.

The latest paper shows data for “Within Breed Proportional Mortality” (WBPM). This is a way to look at the relative differences between the various causes of death for each breed where there were sufficient reports. (Unfortunately, from my personal point of view there were too few Dachshund reports to be included in this analysis).

This is where the paper gets really interesting. The data shows, for example that the WBPM for “old age” ranged from 3.85% in Bernese Mountain Dogs to 25.0% in Bearded Collies. In other words, significantly fewer BMDs die of old age than Bearded Collies. The WBPM for ‘cancer – unspecified’ ranged from 0.00% in Gordon Setters to 19.56% in Flat Coated Retrievers. The WBPM for ‘heart failure’ ranged from 0.00% in Whippets to 19.82% in Cavalier King Charles Spaniels. Again, these reflect what most people know about cancer risk in FCRs and heart disease in Cavaliers. The analysis also shows that Border Terriers had the highest WBPM for dying as a result of road traffic accidents.

This WBPM data enabled the authors to identify how individual breeds’ causes of death compared with the Overall Proportional Mortality (OPM) based on reports for all the dogs in the survey. Boxers and FCRs were the 2 breeds less likely to die of old age compared with the OPM. Cavaliers were less likely to die of cancers, compared with the OPM, but, as you would expect, were more likely to die of heart conditions. If your breed is among the 25 analysed in this way, it’s well worth looking at the data to see how it compares with your own experience.

Healthspan vs. Lifespan

Healthspan is an interesting concept that has become quite topical. A dog’s healthspan is the length of time it is healthy, not just alive. The paper says “Although death may be postponed by improved healthcare, extended longevity by itself does not necessarily imply an improved or even a good quality of life, so a delicate balancing act exists between longevity and acceptable quality of life.” This leads to challenging ethical debates about whether a shorter but healthy lifespan with a short, rapid decline to death, might be preferable to a longer life with long periods of illness and a slow decline to death. There is, inevitably, a difficult decision to be made by owners, with vets, about treatment options to prolong life, quality of life and when might be the right time to consider euthanasia.

The concept of healthspan means that longevity almost certainly means different things in different breeds. A giant breed would, typically, be expected to die younger than a toy breed but as long as the dog was healthy during that lifespan, most people would not consider there to be welfare issues. Conversely, long-lived breeds should not necessarily be considered as being “healthier”, particularly if much of their lifespan is subject to a debilitating illness.

4 categories of breed

The authors merged the results of longevity by breed with Within Breed Proportional Mortality (WBPM) and came up with 4 categories of breed:

  1. Long-lived with no specific cause of death at a raised proportional mortality (e.g. WHW Terrier, Bearded Collie, Gordon Setter)
  2. Long-lived with at least one cause of death at a raised proportional mortality (e.g. Labrador, Golden Retriever, Border Collie)
  3. Short-lived with no specific cause of death at a raised proportional mortality (e.g. GSD, Whippet)
  4. Short-lived with at least one cause of death at a raised proportional mortality (e.g. Flat Coated Retriever, Dobermann)

Category 4 breeds are short-lived with serious, breed-specific, life-limiting conditions. Categories 1 and 3 are breeds where there is a wide variation in longevity associated with factors that apply across all dogs (such as size) and there is no obvious disease that accounts for death.

The paper concludes: “This study has identified individual breeds that have both a low median lifespan and also a high proportional mortality for one or more specific causes of death. Breeds with this combination are highlighted with potential welfare concerns that may need to be addressed.”

If your breed is one of the 25 breeds with causes of death with more than 50 reports, the paper is well worth reading and reflecting on what actions your breed clubs might need to be taking.

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