The popular notion that a ten-year-old dog corresponds to a seventy-year-old person, based on the seven-year rule, may not be accurate, as dogs mature at different rates throughout their lives. Research published in the journal Cell Systems used DNA modifications to establish a more precise correlation between the age of animals and that of humans.
The study analyzed blood samples from 104 Labrador dogs, ranging from puppies up to sixteen years of age. To develop this new calculation method, the researchers examined canine DNA methylation and compared it with the DNA of approximately 304 human individuals, whose ages varied from 1 to 103 years.
Genetic methylation is defined as a chemical process that inserts small molecules into DNA, acting as a type of switch capable of turning genes on or off. In the context of this study on dogs, DNA methylation served as an aging marker, as its patterns change as the organism progresses in age.
The findings demonstrated that the rate of animal development is quite variable. It was observed that canine aging occurs very rapidly in the first months and years of life, but this speed significantly decreases as the pet ages.
To represent this curve mathematically, the team of scientists created an equation based on logarithms: the equivalent human age is determined by multiplying the natural logarithm of the animal's age by 16, plus 31 (formula: human age = 16 × ln(dog's age) + 31).
However, the analysis has an important limitation, indicating that this formula should not be seen as a rule applicable to all dogs. Since the study was conducted exclusively with the Labrador Retriever breed, other lineages may exhibit different aging processes.
Additionally, the physical size of the animal also influences this process. Generally, larger breed dogs tend to age faster and have a shorter life expectancy compared to small-sized dogs. Thus, the correspondence between canine and human age can change depending on the breed and the individual characteristics of each animal.
Therefore, the formula presented by the researchers should primarily be understood as an estimate of biological aging, and not as an exact conversion of any dog's age to human years.