A 15-year-old cat is roughly equivalent to a human aged around 80
A 15-year-old cat is not simply an ‘elderly pet’. According to a new biological model, it is roughly equivalent to a human aged around 80. Scientists reached this conclusion by comparing thousands of data points on ageing in cats, humans and other mammals.
The main idea behind the study is that domestic cats can serve as a useful natural model of ageing. They live alongside humans, live to a very old age and, as they age, exhibit changes in the brain similar to those seen in humans.
The study has been published in the journal Biology Open.
This does not mean that a cat’s brain ages in exactly the same way as a human’s. However, the similarities are striking enough for scientists to suggest studying older cats more closely — including to gain a better understanding of healthy ageing and age-related brain diseases.
Details
The researchers used 3,754 observations, including brain MRI scans, blood test results, clinical records, age-related changes and developmental stages in cats, humans and other mammals. They did not simply convert age using the formula ‘one cat year equals several human years’, but instead built a model based on measurable biological characteristics.
Brain scans were particularly important. In both cats and humans, similar processes occur with age: the brain gradually loses volume, whilst the cerebral ventricles — cavities filled with fluid — expand. Such changes are often associated with ageing and age-related decline in brain function.
According to this model, it turns out that the later stages of life in cats and humans can be compared. One example from the study: an 80-year-old human roughly corresponds to a 15-year-old cat.
Why cats have caught the attention of scientists
Many laboratory animals have a very short lifespan or do not age in the same way as humans. Furthermore, diseases are often induced artificially in them in order to study a specific process.
The situation is different with cats. Domestic cats age naturally, live in a normal environment, suffer from age-related illnesses and are increasingly undergoing veterinary examinations, including MRIs. They can therefore provide data on ageing under real-world conditions, rather than just in the laboratory.
Another advantage is their lifespan. Cats live for much shorter periods than humans, so age-related changes can be observed more quickly. At the same time, they live long enough to reach stages similar to human old age.
What this could mean for humans
If scientists gain a better understanding of how cats’ brains age, this could help in studying brain ageing in humans. Of particular interest are changes associated with neurodegeneration, cognitive decline and age-related diseases.
This approach is also beneficial for the animals themselves. If veterinary and medical databases are developed in tandem, this could improve the diagnosis of age-related diseases in cats whilst simultaneously providing more information about human ageing.
Why this isn’t just another ‘cat age’ conversion table
Popular conversion tables often state that a 1-year-old cat is equivalent to a certain number of human years, a 5-year-old to another number, and a 15-year-old to yet another. But such schemes are far too simplistic.
New research shows that ageing does not proceed at a constant rate throughout life. At different stages, the body develops and ages in different ways. Therefore, rather than comparing calendar years, the scientists compared actual biological indicators: the brain, blood, development and age-related changes.
This is precisely why the phrase ‘a 15-year-old cat is roughly equivalent to an 80-year-old human’ is not a matter of everyday arithmetic, but the result of a biological comparison.
Source
Study: Capucine Januel et al., “Cat brains age like humans: Translating Time shows pet cats live to be natural models for human ageing”, Biology Open, 2026.