Half of all statistics are made up.

Who knows the real answer to this one. Not unlike any other profession, if you eat right, exercise regularly and maintain a healthy lifestyle you shouldn't have any problem living well into your retirement years.

There is no doubt that night flying is tougher on your body than working during normal daylight hours. Some can handle it very well, others mediocre, and still others cannot do it - everyone is a little different.

I think the time of day and type of flying (domestic vs international) are just factors of a much bigger equation. The big question that should be asked is if the person in question is maintaining a healthy lifestyle overall. The next big question that should be asked is one regarding the stress levels of one's given occupation. i.e., flying nights vs one who works 60+ hours a week in the office.