As practicing veterinarians, we share and discuss with each other about complicated and challenging cases. Either to get some support or to learn from each other. One of the most bizarre types of cases that we can’t find good scientific proof or explanations yet, are “sympathy illness.”
A dog has been limping for one week, after the X-ray, he is diagnosed with cranial cruciate ligament tear. ( Same as ACL in people) The owner is in shock because she herself had just recovered from an ACL surgery.
A dog has really bad skin allergies with secondary infections, and as I’m explaining and suggesting the allergy testing, the owner nods and interrupts me, “I know all too very well of the allergy tests, because I grew up with very bad eczema.”
A cat starts losing weight and drinks lots of water, once he is diagnosed with diabetes, the owner says to the cat, “Buddy, now we both need to get the insulin shots.”
Sometimes the similarities between the pets’ and the owners’ conditions could be as mild as a loose knee cap, but sometimes, it would be as sad as an aggressive form of cancer.
I’m not sure if there’s a specific term for this types of scenarios, and “sympathy illness” is the closest one I could find.
One of the most likely explanations, is that statistically, many degenerative diseases, including osteoarthritis and cardiovascular diseases, are commonly seen in both aged pets and senior citizens. Therefore, it is not surprising that a 13 year-old Labrador, who belongs to a 75 year-old gentleman, has arthritis, just like his owner.
Granted, indoor pets and humans share the same living environment, as a result, they are under exposure of similar risks, such as chemicals, pollutions, and cigarette smoke. Please see the links of an Scientific American article and the Golden Retriever Lifetime Study webpage provided below for details.
As part of a company that supports evidence based products and recommendations, I won’t go deep into personal opinions and assumptions here. However, I do believe that the relationships between us and our pets, the bond we share with each other, and the impact we have towards each other’s life, are more profound than we think.
That means, when we take good care of our pets, we will start taking better care of ourselves. That means, when we are more involved in our own health, our pets will be benefit from it as well.That means, don’t wait on either. No matter which direction you pick, start offering both yourself and your pet(s) a better life!​

https://www.scientificamerican.com/article/pets-share-owners-diseases/
https://www.morrisanimalfoundation.org/golden-retriever-lifetime-study