Re: Horse and human age correlation?

Dear Heather,

This was a much more difficult question to find ANY information on than I had anticipated. I searched through my personal horse books as well as most of the equine text books at the CSU Vet Library. I also did a search on the Vet data base and found nothing. So I then asked around. No one I asked had heard of a specific formula, but several people gave their input.

One of the doctors I work with, Dr. A.S. Turner stated that since horses will live until 30 or 40 years of age (sometimes a bit more even) that it is likely around 2 years per 1 year of humans, as a 40 year old horse is quite old, and not nearly as many horses make it to 40 as they do 30. This would be similar to 80 and 60 in humans. However, Sandi Crowe, a radiologist tech and long time horse breeder stated that horses are teenagers from about 2-3 years of age. This is when they reach sexual maturity, reach nearly their adult size, and generally act like independent brats. (Yep, definitely teenagers). Now, if our hypothesis of 2 to 1 were to hold up, then horses should be teenagers from about 6 years to 10. But since this isn't the case, we can look the other way and say that 2-3 horse years correlates to 12-18 humans years in a 6 to 1 ratio. But if 6 to 1 were the ratio, then a 40 year old horse would be 240 years old in human years! See the problem?

What I concluded from my search is that the reason you don't hear about a simple equation for estimating horse to human years is that it is non-linear. This means that it isn't a simple number, like multiplying by 7, as it is for dogs. It is likely a logarithmic or negative exponential curve, which obviously isn't easy to explain! However, you can estimate by starting at 6:1 when they are young and gradually decreasing it until 2:1 when they are probably in their mid-20's. (Dogs and cats are similar but they tend to get to that 7:1 ratio by the time they are 3, so it makes a better estimate for them, but they do reach their teenage years much faster than the 7:1 ratio indicates). Hope this helps.

If you want a cool project to do, research racetrack horse longevity and working horse longevity, and correlate when they stop racing or working, as compared to humans, to get a good estimate of equine mid-life age correlations. (Meaning the time most racehorses retire is likely to correspond to a humans low to mid 30's since this is when most pro athletes retire. In working horses the average retiring age will likely correspond to 50's in human years). Once these are plotted, an actual equation or table could be made. Would be cool and might even be recognized by the AVMA or similar group. Again, hope that I answered your question.

BK