As a veterinary epidemiologist my interest and passion lies in the investigation of causes of disease in companion animals and how to prevent them from occurring. One clear benefit of an epidemiological study such as a prospective cohort study is that the knowledge gained can be used to help members of the target population extend their healthspan, defined as the number of years in which an individual is generally healthy and free from serious disease.
Unlocking the secrets of successful aging
In 2015 I was invited to be part of a team to evaluate the results of 10+ years observation of a group of 39 Labrador retrievers; almost one-third (28%) of these Labradors achieved an exceptional age, reaching or exceeding 15.6 years. This exceptional age was defined by taking the breed`s average age of 12 and extending it by 30%. We were interested in trying to unlock some of the secrets of successful ageing as increasing the healthspan of dogs will benefit both the pet and their owners.
Could our ‘oldest of the old’ canine companions give us some clues to how we can age successfully?
But why should these Labradors be of interest to humans and our ageing process? The interest lies in the fact that a 15.6 year-old Labrador represents ̴95 years in human physiological age. The oldest dog, a male called Utah, died 5 weeks before his 18th birthday, a human equivalent age of ̴109 years, making him almost a supercentenarian in human terms (meet Utah and some of the other dogs). Could our ‘oldest of the old’ canine companions give us some clues to how we can age successfully?
Aiming to understand the process
A leading veterinary gerontologist, Professor David Waters, from Purdue University College of Veterinary Medicine, Indiana, USA, is well known for his work on the subject of extending human healthspan.
He has studied highly successful ageing in the domestic dog, Canis lupus familiaris, particularly in the Rottweiler breed. The ultimate goal is to fully understand the process of highly successful ageing, including cancer resistance, in both our domestic dogs and people; this has been captured in a 13-minute talk by Professor Waters on YouTube, shown below.
What did we find?
For an epidemiologist, this observation of longevity in Labradors, published today in Acta Veterinaria Scandinavica, produced some exciting results. Almost 90% of the Labradors exceeded the breed`s expected average age of 12 and five dogs went on to become 16 or 17 years of age.
Why did some Labradors live to 16 or 17 and others only reached their expected average age of 12 or even below?
When compared to other groups of Labradors, this group showed a significant increase in their lifespan. Why did some Labradors live to 16 or 17 and others only reached their expected average age of 12 or even below? Could their experience help in developing strategies that increase the healthspan of humans?
For humans, the ‘oldest of the old’ (centenarians) demonstrate a compression of morbidity; they have ‘compressed’ diseases into the last few years of their 100+ life that would have typically caused illness and death at a younger age. Our 16-17 year old Labradors represent 99-104 year old humans. What ‘compressions’ did they achieve and what can we learn about highly successful ageing?
We found that the longest lived Labradors, the 28% that became exceptionally aged (≥15.6 years old), had a significantly slower rate of body fat mass accumulation over their first 13 years of life compared to Labradors that lived only to their expected average age of 12 or less.
They also had a significantly slower loss of lean body mass compared to those with the shortest lifespan. An important component of lean body mass is muscle mass; loss of muscle mass and strength in the absence of disease is called sarcopenia.
In humans, age-related sarcopenia fits the current definition of a geriatric syndrome: conditions that result from incompletely understood interactions of disease and age on multiple body systems, producing a collection of signs and symptoms. Sarcopenia is associated with an increased risk of adverse outcomes such as physical disability, poor quality of life and death.
Do dogs hold the key?
We are now interested to further evaluate the changes in body fat and lean body mass to see if they could hold the key as to why some dogs did, and some did not, reach an exceptional age.
We are now interested to further evaluate the changes in body fat and lean body mass to see if they could hold the key as to why some dogs did, and some did not, reach an exceptional age. Such knowledge could be applied to the human ageing model and aid in the development of strategies to improve our chance of healthy ageing and to extend healthspan.
It must be noted that the Labradors included in the longevity observations were fed to maintain a body condition score of between 2 and 4 on a 5-point scale in order to avoid excessive weight gain that has been previously linked to musculoskeletal disease and decreased longevity. Interestingly, just this week an obesity gene (POMC) has been identified in Labradors by Dr Eleanor Raffan and other scientists at Cambridge University.
So, the next time you stroke your ageing dog and look lovingly into their eyes, just think that they could hold the keys to some of the secrets as to how we could also age successfully.