What factor might cause a Collie mix's expected lifespan average to be pulled down significantly?

Answer

A cross with a significantly larger breed

A cross with a significantly larger breed, such as a Great Dane or Mastiff, will almost certainly reduce the lifespan average due to heightened risks of orthopedic problems and certain cancers.

What factor might cause a Collie mix's expected lifespan average to be pulled down significantly?
DoglifespanmixCollie