Dogs start to age at the age of 6. How can we make them live longer and healthier?

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Large dogs may have shorter life spans, but are less likely to suffer from Alzheimer's.

It is enough to feed your dog one meal a day.

Eat a balanced diet. Extra supplements may not be very helpful.

· Exercise more, get sterilized, and age slower.

There are already hundreds of millions of pet dogs in the world.

The life span of a dog is only a dozen years. The speed at which a dog ages is much faster than that of a human.

This is sad news for dog owners, meaning that once you get a dog, you may have to watch it die in ten years.

There is a saying on the Internet that in the eyes of dogs, humans are like elves, an "immortal race" that can easily live for 500 years .

Owners know that dogs may show signs of "aging" after the age of 6. When dogs age, they may lose teeth, lose hair, have poor vision and hearing, gain weight, suffer from joint disease, lose energy, weaken muscle strength, and have a weakened immune system.

However, there is no sufficiently objective "dog aging standard" so far, because no one has studied "canine gerontology".

It was not until 2014 that three scientists from the University of Washington launched the Dog Aging Project [1].

This project aims to find out two things: First, how do dogs age? Second, is there any way to slow down their aging?

The Dog Aging Project is launched

The Dog Aging Research Project is a big project[2].

More than 100 researchers and nearly 40,000 pet dogs and their owners have joined this large-scale, long-term longitudinal research project , and follow-up research will last at least 10 years[3].

They are also collaborating with a much older project called the Family Dog Project, which was started by researchers at Eötvös Loránd University in Hungary in the 1990s to study “behavior and cognition between dogs and humans.”

Scientists from the Family Dog Research Project are teaching dogs to lie still in an MRI scanner. | Video screenshot of Training dogs to lie still in MRI scanner

Generally speaking, the larger the mammal, the longer its life span. Cats and dogs usually live for more than ten years, while cattle and horses live for several decades.

However, this rule does not apply within the same species. Large dogs grow faster and die earlier than small dogs . A small dog weighing around 10 kg can live for more than ten years, while a large dog weighing more than 60 kg will hardly live more than ten years. For example, the average lifespan of a large Bernese Mountain Dog is only 7 years, while the average lifespan of a small Chihuahua is 15 years. A 2013 study[4] concluded that for every 2 kg increase in weight after adulthood, a dog's lifespan is shortened by about one month.

The smaller the dog, the longer its average lifespan. |References[4]

For researchers, pet dogs are excellent research subjects.

First, the life span of a dog is only a dozen years at most. If the study starts at the age of 6, the obvious aging process of the dog can be observed and recorded within a few years . In contrast, if an animal with a life span close to that of humans is selected for research, such as an elephant, then the research funds may be spent, and the elephant may still eat bananas calmly and without much change.

Second, there are enough pet dogs, their genes are genetically diverse, and they live with humans in a variety of family environments. Compared with mice in the laboratory that have a monotonous environment, a monotonous and repetitive diet, and highly similar genetics, pet dogs are more like humans in reality with "diverse genes, diverse environments, and diverse experiences." Therefore, the data of pet dogs is more valuable for reference to humans.

Third, dogs and humans share more than 17,000 homologous genes . The effects of many genes can be studied in dogs. For example, if the SCN3A gene mutates, it will affect language development and cause epilepsy in humans; the same gene mutation will also affect the tone of a dog's howl[5]. For another example, narcolepsy. Scientists have long speculated that it may be some autoimmune system problem that causes daytime sleepiness or sudden sleepiness. The final breakthrough point was also in dogs. Researchers found related genes in Doberman Pinschers that affect both the nervous system and the immune system.

Doberman Pinscher | akc.org

Finally, the owners who signed up to participate in this study loved their dogs and were willing to take the time and effort to collect and provide various data.

With the joint efforts of countless owners, this project has made many discoveries.

Old dogs are less susceptible to dementia, and old dogs can learn new tricks

The first finding was that large dogs, although they had a shorter lifespan, were less likely to develop Alzheimer's .

Just like humans can suffer from Alzheimer's disease, dogs can also develop cognitive impairment (Canine Cognitive Dysfunction) in old age.

Just as humans donate their bodies for scientific research, some owners have reluctantly donated their pet dogs’ bodies for research into what happens in their dogs’ brains. It turns out that, like humans, dogs also have elevated levels of amyloid-β in their brains.

Large dogs have shorter lifespans, but does this mean that they also decline more quickly in cognitive abilities?

A 2020 study[6] compared more than 4,000 dogs of 66 breeds, using nine tasks to test the dogs’ cognitive abilities. The results found that the data were more consistent with the “truncation” hypothesis than the “acceleration” hypothesis .

That is to say, regardless of size, the cognitive abilities of all dogs follow a similar development rate, first upward and then declining. Big dogs do not "accelerate Alzheimer's disease."

Older dogs die earlier and at a stage when they are more cognitively capable . Smaller dogs live longer but may experience more significant cognitive decline later in life.

Two hypotheses about dog cognitive abilities. The left one is the "truncation" hypothesis, and the right one is the "acceleration" hypothesis. | References [6]

The second discovery is that old dogs can learn new tricks .

In 2020, researchers from the Smart Dog Lab in Vienna conducted a series of cognitive tests on 119 pet dogs (>6 years old)[7] and found that the older the dogs, the less courageous they became, their curiosity weakened, their interest in playing decreased , they were less willing to approach strangers or explore new environments, and their problem-solving ability also declined.

However, trainability, sociability, and independence in activities do not significantly weaken even as dogs age .

For certain specific tasks, such as learning to make eye contact with trainers, the old dogs performed just as well because they were rewarded with sausages after success.

Teaching old dogs new tricks is also helpful in delaying their aging and maintaining their cognitive abilities . It is recommended that owners play more games with their dogs at home when they have time, such as hiding snacks for them to find.

This study also tested the effect of giving dogs nutritional supplements. Some owners gave their dogs additional supplements (vitamin C, vitamin E, fish oil DHA, serine, tryptophan, tea polyphenols), but in this study, these supplements did not significantly improve the dogs' cognition .

In addition, lifelong training in dog schools does not seem to have as many benefits as expected, with only some positive effects on attention, but no benefits on learning speed or cognitive flexibility.

Doing this will slow down the aging of dogs

Eat one meal a day

A 2022 study[8] found that dogs that ate only one meal a day (about 8% in the study) were healthier, smarter, and had a lower risk of various diseases than dogs that ate two or three meals a day or even "always had food in their bowls."

For example, compared with other dogs, dogs that eat one meal a day have a 59% lower risk of hepatopancreatic disease, a 35% lower risk of gastrointestinal disease, a 29% lower risk of urinary system disease, a 21% lower risk of orthopedic disease, and a 16% lower risk of dental and oral disease.

Relative risk of disease, blue is statistically significant, yellow is statistically insignificant. | References [8]

And the dogs that ate less had better cognitive abilities, too. "It's like the difference between a 7-year-old and an 11-year-old," said researcher Emily Bray.

However, Bray also pointed out that this study does not directly recommend that owners feed their dogs once a day. "Even if we really find that dogs are healthier if they eat once a day, we should consider other factors, such as the dog's own preferences and expectations."

Exercise more

People who exercise more age slower, and dogs who exercise more also age slower.

In 2022, a study by the "Dog Aging Project"[9] tracked 11,574 dogs and found that the more exercise a dog got every day, the lower its risk of developing dementia. Dogs with high levels of exercise had a dementia risk of only 53% of that of other dogs.

In addition to physical exercise, mental training is also effective. Dogs that regularly undergo mental challenges also have a lower risk of dementia.

The study also found that dogs who took daily neuroprotective supplements such as fish oil were also associated with a lower risk of dementia.

Finally, I would like to remind you that this study is a correlation study and cannot completely establish a causal relationship. Theoretically, it is also possible that cognitive decline has caused dogs to become less active.

Speaking of exercise, a 2022 study[10] showed that large dogs exercise more than small dogs, and dogs living in the countryside exercise more than dogs living in cities. And surprisingly, the older the owner, the more exercise a dog gets.

The researchers speculate that this may be because older people have more free time than younger people, work fewer or more flexible hours, and do not have to take care of children (this is a US study).

Dogs who get more exercise have a significantly lower risk of developing dementia | petbasics.com

Cut off for permanent rule

If you don't plan on letting your dog have children, have it neutered as soon as possible.

A 2022 British study[11] found that it is better to neuter dogs early, regardless of gender. Neutered dogs have a longer life expectancy than dogs that have not been sterilized .

In dogs, although giving birth is beneficial to "extending life", it is not beneficial to "extending their own life".

However, neutered dogs may not be as obedient to your instructions. Studies[12][6] have shown that neutered dogs are more interested in food and less interested in "instructions from their owners."

So, you might end up with a long-lived dog that loves food and is chubby, but doesn't really pay attention to your commands.

Anti-aging drugs may help

In 2017, 24 pet dogs (>6 years old, >16 kg) participated in a small clinical trial[13], of which 16 were given rapamycin (0.05 mg/kg or 0.1 mg/kg orally three times a week) and 8 were given a placebo over a 10-week period.

Rapamycin was originally used to suppress immune rejection after organ transplantation, but it was later found to extend the lifespan of yeast, nematodes, fruit flies, and mice. Now, the drug is also being considered as a potential anti-aging drug for humans.

The results showed that compared with dogs using a placebo, the dogs using rapamycin had no obvious side effects and improved heart function. In addition, in the higher-dose rapamycin group, 70% of dog owners believed that their dogs were more energetic and exercised more. The researchers speculated that rapamycin's anti-inflammatory effect may have reduced the pain caused by arthritis in dogs .

Of course, rapamycin still needs larger-scale and longer-term studies. The next plan of the "Dog Aging Project" is to track the effects of rapamycin on 500 dogs for three years. Dog owners may wish to pay attention to this promising study.

How can I sleep without seeing your smile｜Unsplash

Conclusion

Over the next decade, the Dog Aging Project will work to unravel many of the mysteries of dogs and gain new insights.

There are still many things scientists want to study:

What intelligence do dogs have?

How do dogs perceive the world around them, and how does that perception change as they age?

After artificial intelligence analyzes big data, can it obtain the genome of a puppy and predict the dog's future appearance, personality and disease risks?

Bernese Mountain Dogs have a 225-fold risk of developing malignant histiocytosis[14]. Are there differences in the risk of other dog breeds developing various diseases?

Are there any special genetic features in the longevity of dogs? And can these special features be replicated in humans?

…

Dogs are the first animals domesticated by humans . Our two species have been together for tens of thousands of years.

There was a time when “dogs barked in the sound of water, and peach blossoms were covered with dew”. There was also a time when “dogs barked behind the wooden door, and people returned home in the wind and snow”.

Although time has passed, the relationship between people and dogs remains as Du Fu wrote, "The old dog is happy to see me return and lingers at the hem of my clothes."

References

[1]Dog Aging Project. (2022, May 11). Retrieved from https://dogagingproject.org

[2] Ogden, LE (2022). Inside the brains of aging dogs. Knowable Magazine | Annual Reviews. doi: 10.1146/knowable-072622-1

[3]Creevy, KE, Akey, JM, Kaeberlein, M., Promislow, DEL, Dog Aging Project Consortium, Barnett, BG, ...Wilfond, BS (2022). An open science study of ageing in companion dogs. Nature, 35110758. Retrieved from https://pubmed.ncbi.nlm.nih.gov/35110758

[4]Selman, C., Nussey, DH, & Monaghan, P. (2013). Ageing: It's a Dog's Life. Current Biology, 23(10), R451–R453. doi: 10.1016/j.cub.2013.04.005

[5]Morrill, K. (2022). Dog and Human Genetics: Similarity and Difference. Dog Aging Project. Retrieved from https://dogagingproject.org/dog-and-human-genetics-similarity-and-difference

[6]Watowich, MM, MacLean, EL, Hare, B., Call, J., Kaminski, J., Miklósi, Á., & Snyder-Mackler, N. (2020). Age influences domestic dog cognitive performance independent of average breed lifespan. Animal cognition, 23(4), 795-805.

[7] Chapagain D, Wallis LJ, Range F, Affenzeller N, Serra J, Virányi Z (2020) Behavioral and cognitive changes in aged pet dogs: No effects of an enriched diet and lifelong training. PLoS ONE 15(9): e0238517. https://doi.org/10.1371/journal.pone.0238517

[8]Bray, EE, Zheng, Z., Tolbert, MK, McCoy, BM, Kaeberlein, M., & Kerr, KF (2022). Once-daily feeding is associated with better health in companion dogs: results from the Dog Aging Project. GeroScience, 1-12.

[9]Bray, EE, Raichlen, DA, Forsyth, KK, Promislow, DEL, Alexander, GE, MacLean, EL, & . (2022). Associations between physical activity and cognitive dysfunction in older companion dogs: Results from the Dog Aging Project. bioRxiv, 2022.04.20.488879.

[10]Lee, H., Collins, D., Creevy, KE, Promislow, DE, Akey, JM, Benton, B., ... & Dog Aging Project Consortium. (2022). Age and Physical Activity Levels in Companion Dogs: Results From the Dog Aging Project. The Journals of Gerontology: Series A.

[11]Teng, KT-y., Brodbelt, DC, Pegram, C., Church, DB, & O'Neill, DG (2022). Life tables of annual life expectancy and mortality for companion dogs in the United Kingdom. Scientific Reports, 12, 1–11. doi: 10.1038/s41598-022-10341-6

[12]Scandurra, A., Alterisio, A., Di Cosmo, A., D'Ambrosio, A., & D'Aniello, B. (2019). Ovariectomy impairs socio-cognitive functions in dogs. Animals, 9(2), 58.

[13]Urfer, SR, Kaeberlein, TL, Mailheau, S., Bergman, PJ, Creevy, KE, Promislow, DEL, & Kaeberlein, M. (2017). A randomized controlled trial to establish effects of short-term rapamycin treatment in 24 middle-aged companion dogs. GeroScience, 39(2), 117. doi: 10.1007/s11357-017-9972-z

[14]Shaiken, LC, Evans, SM, & Goldschmidt, MH (1991). RADIOGRAPHIC FINDINGS IN CANINE MALIGNANT HISTIOCYTOSIS. Veterinary Radiology, 32(5), 237–242. doi: 10.1111/j.1740-8261.1991.tb00113.x

Author: You Shiyou

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