Larger dog breeds such as Great Danes, Burmese Mountain Dogs, Newfoundlands, Irish Wolfhounds, etc. don’t live as long as average dogs because their organs are so large, and their bodies are so big that it takes a lot to keep the body going. Especially when the dogs are tall, the blood sometimes can’t get to the bottom of the paw, that’s why a lot gnaw on their paws when they’re older; heart problems are common.
A lot of larger breeds have high risk to bloat and hip dysphasia also.
They just have to deal with all the health issues they’re prone to have.