Dogs in a healthy aging study were required to be at least 40 pounds and 6 years old, with no pre-existing conditions, to approximate a human equivalent of 55 years.

“so we enrolled dogs into this study this was a very small study all for it at a private veterinary specialty clinic in the Seattle area and so the dogs had to be at least 40 pounds and at least 6 years old and they could not have any pre-existing conditions so again this is a study of healthy aging we wanted healthy dogs coming into the study six years old at that weight range we figured that that would be you know roughly the human equivalent of 55 years maybe big dogs age faster than small dogs so that's why we had the weight criteria”