Exploring mechanisms of sex differences in longevity: lifetime ovary exposure and exceptional longevity in dogs.

To move closer to understanding the mechanistic underpinnings of sex differences in human longevity, we studied pet dogs to determine whether lifetime duration of ovary exposure was associated with exceptional longevity. This hypothesis was tested by collecting and analyzing lifetime medical histories, age at death, and cause of death for a cohort of canine 'centenarians'--exceptionally long-lived Rottweiler dogs that lived more than 30% longer than average life expectancy for the breed. Sex and lifetime ovary exposure in the oldest-old Rottweilers (age at death, > or = 13 years) were compared to a cohort of Rottweilers that had usual longevity (age at death, 8.