Domestic Dogs (Canis Familiaris)

Domestic dogs (canis familiaris) have become increasingly popular as model organisms in longevity research due to their diverse breeds, sizes, and lifespans. This makes them excellent subjects for studying aging and its related processes.^[1]^[2]

Reasons for Choosing Dogs

Dogs share many environmental exposures with humans and exhibit a wide range of lifespans and physiological traits. This diversity provides a unique opportunity to study the genetic and environmental factors affecting longevity. Additionally, their close living proximity with humans allows for the assessment of environmental influences on morbidity and mortality in both species. Recently, the companion dog has been proposed as a powerful model to better understand the genetic and environmental determinants of morbidity and mortality in humans.

Comparative Biology of Aging in Dogs

Survivorship (a) and hazard curves for (b) for human (left) and dogs (right). Human data are from the U.S. Census Bureau (1972–2002), and canine data come from the VetCompass database (2010–2013). For both species, colors represent the two sexes, female (red) and male (blue). ^[1]

The biology of aging in dogs varies significantly across breeds, offering insights into how genetic diversity influences aging. Studies on canine aging also help in understanding age-related diseases and their progression. Comparative analyses of morbidity and mortality between humans and dogs have shown significant similarities in the effects of age on disease risk, especially in neoplastic, congenital, and metabolic causes of death. Furthermore, research has emphasized the value of studying aging in dogs to improve dog health and support translational discoveries for humans.

Genetic Factors in Canine Longevity

Research into the canine genome has identified various genetic factors that contribute to their longevity. These findings are crucial for understanding the genetic basis of aging and developing interventions to extend healthy lifespan. The history of intense breeding in dogs for specific traits has resulted in a species with considerable genetic variation among breeds, which is valuable for studying genetic influences on longevity and disease. In particular, variations in genes like IGF1, which is linked to size and longevity in dogs, provide critical insights into the genetic underpinnings of aging.

Environmental and Lifestyle Factors

Factors such as diet, exercise, and living conditions play a significant role in the longevity of dogs. These aspects offer valuable insights into how lifestyle choices impact aging and healthspan. Dogs' exposure to diverse environments, often mirroring those of humans, makes them ideal for studying the impact of environment on aging. This includes evaluating the role of environmental toxicants that target stem cells, accelerating aging and age-related diseases.

Human-Canine Health Comparisons

A large-scale comparison of human and canine patterns of morbidity and mortality has revealed that many chronic conditions common in humans, such as obesity, arthritis, and diabetes, are also prevalent in dogs. This similarity extends to the association with comorbidities, suggesting that dogs can be a powerful model for studying human health issues. However, there are differences in certain areas, such as cardiovascular disease, highlighting the need for detailed comparative studies.

Morbidity and Comorbidity Analysis

Studies have shown that dogs exhibit multimorbidity with age, similar to humans, and that specific chronic conditions in dogs are associated with an increase in comorbidity number. This similarity suggests that companion dogs may provide an ideal model to study multimorbidity and comorbidity in humans. Additionally, cognitive aging in dogs, as shown in studies on breeds like Beagles, provides valuable insights into the progression and management of age-related cognitive decline.

Limitations and Future Research Directions

Current studies have limitations, such as reliance on data from veterinary teaching hospitals, which may not represent the general canine population. There is a need for more detailed data from canines representing a full diversity of ages, breeds, comorbidities, and environments. Future longitudinal studies of aging in dogs could provide more accurate insights into human morbidity and mortality. The recent launch of large-scale studies like the Golden Retriever Lifetime Study and the Dog Aging Project underscores the growing importance and potential of canine models in aging research.

References

↑ ^1.0 ^1.1 Hoffman JM et al.: The companion dog as a model for human aging and mortality. Aging Cell 2018. (PMID 29457329) [PubMed] [DOI] [Full text] Around the world, human populations have experienced large increases in average lifespan over the last 150 years, and while individuals are living longer, they are spending more years of life with multiple chronic morbidities. Researchers have used numerous laboratory animal models to understand the biological and environmental factors that influence aging, morbidity, and longevity. However, the most commonly studied animal species, laboratory mice and rats, do not experience environmental conditions similar to those to which humans are exposed, nor do we often diagnose them with many of the naturally occurring pathologies seen in humans. Recently, the companion dog has been proposed as a powerful model to better understand the genetic and environmental determinants of morbidity and mortality in humans. However, it is not known to what extent the age-related dynamics of morbidity, comorbidity, and mortality are shared between humans and dogs. Here, we present the first large-scale comparison of human and canine patterns of age-specific morbidity and mortality. We find that many chronic conditions that commonly occur in human populations (obesity, arthritis, hypothyroidism, and diabetes), and which are associated with comorbidities, are also associated with similarly high levels of comorbidity in companion dogs. We also find significant similarities in the effect of age on disease risk in humans and dogs, with neoplastic, congenital, and metabolic causes of death showing similar age trajectories between the two species. Overall, our study suggests that the companion dog may be an ideal translational model to study the many complex facets of human morbidity and mortality.
↑ Ruple A et al.: Dog Models of Aging. Annu Rev Anim Biosci 2022. (PMID 34699257) [PubMed] [DOI] [Full text] As the most phenotypically diverse mammalian species that shares human environments and access to sophisticated healthcare, domestic dogs have unique potential to inform our understanding of the determinants of aging. Here we outline key concepts in the study of aging and illustrate the value of research with dogs, which can improve dog health and support translational discoveries. We consider similarities and differences in aging and age-related diseases in dogs and humans and summarize key advances in our understanding of genetic and environmental risk factors for morbidity and mortality in dogs. We address health outcomes ranging from cancer to cognitive function and highlight emerging research opportunities from large-scale cohort studies in companion dogs. We conclude that studying aging in dogs could overcome many limitations of laboratory models, most notably, the ability to assess how aging-associated pathways influence aging in real-world environments similar to those experienced by humans.

[pmid29457329-1] 1.0 ^1.1 Hoffman JM et al.: The companion dog as a model for human aging and mortality. Aging Cell 2018. (PMID 29457329) [PubMed] [DOI] [Full text] Around the world, human populations have experienced large increases in average lifespan over the last 150 years, and while individuals are living longer, they are spending more years of life with multiple chronic morbidities. Researchers have used numerous laboratory animal models to understand the biological and environmental factors that influence aging, morbidity, and longevity. However, the most commonly studied animal species, laboratory mice and rats, do not experience environmental conditions similar to those to which humans are exposed, nor do we often diagnose them with many of the naturally occurring pathologies seen in humans. Recently, the companion dog has been proposed as a powerful model to better understand the genetic and environmental determinants of morbidity and mortality in humans. However, it is not known to what extent the age-related dynamics of morbidity, comorbidity, and mortality are shared between humans and dogs. Here, we present the first large-scale comparison of human and canine patterns of age-specific morbidity and mortality. We find that many chronic conditions that commonly occur in human populations (obesity, arthritis, hypothyroidism, and diabetes), and which are associated with comorbidities, are also associated with similarly high levels of comorbidity in companion dogs. We also find significant similarities in the effect of age on disease risk in humans and dogs, with neoplastic, congenital, and metabolic causes of death showing similar age trajectories between the two species. Overall, our study suggests that the companion dog may be an ideal translational model to study the many complex facets of human morbidity and mortality.

[pmid34699257-2] Ruple A et al.: Dog Models of Aging. Annu Rev Anim Biosci 2022. (PMID 34699257) [PubMed] [DOI] [Full text] As the most phenotypically diverse mammalian species that shares human environments and access to sophisticated healthcare, domestic dogs have unique potential to inform our understanding of the determinants of aging. Here we outline key concepts in the study of aging and illustrate the value of research with dogs, which can improve dog health and support translational discoveries. We consider similarities and differences in aging and age-related diseases in dogs and humans and summarize key advances in our understanding of genetic and environmental risk factors for morbidity and mortality in dogs. We address health outcomes ranging from cancer to cognitive function and highlight emerging research opportunities from large-scale cohort studies in companion dogs. We conclude that studying aging in dogs could overcome many limitations of laboratory models, most notably, the ability to assess how aging-associated pathways influence aging in real-world environments similar to those experienced by humans.

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