Frequently asked questions
A 2019 University of California San Diego study (Wang et al., published in Cell Systems) used DNA methylation patterns to compare epigenetic ageing between dogs and humans. They found dogs age much faster than humans early on (a 1-year-old dog is biologically ~30) then slow down. The formula 16 × ln(age) + 31 fits their data.
Large dogs age faster. A Great Dane is considered senior at 6-7, a Chihuahua not until 11-12. The reasons aren't fully understood — possibly faster growth = more cell divisions = faster cellular ageing. Small dogs typically live 14-16 years; giant breeds often 7-9 years.
The American Association of Feline Practitioners and the American Animal Hospital Association published a consensus cat life-stage chart in 2010 (updated 2021). Cats have less size variation than dogs, so a single formula works: 15/24/+4 per year after.
It's a 1950s estimate based on rough averages of dog vs human lifespan. It misses that pets age rapidly in their first 2 years and slow down dramatically. A 1-year-old dog is closer to a 30-year-old human than a 7-year-old. Modern research treats it as a myth.
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