The concept that married people live longer is interesting. I'm sure there is some merit to the idea that if you're married there is someone there to nag you about going to the doctor, but I think much larger factors are having the finances of dual incomes and access to an immediate support person.
Surgeries require having a designated person to look after you. Many injuries require driving to somewhere like an emergency room which can be hard to do if you are the one injured. If you're home with the flu, it's hard to tell when it's bad enough to go to the hospital without another person checking on you. And if you pass out it requires another person to find you like that to get medical aid.
You can prop it up as the benefits of marriage, but I think there's a much deeper discussion to be had about how we've built society around marriage as an inevitable conclusion and neglected to build support systems that function outside of romantic pairings.
