I don't doubt this is true, but not sure of the study method. Instead of looking at 10 volunteers for a week or so, they should have actually studied people who work the overnight shifts, for a prolonged period of time.
I've worked the 12am to 8am shift, either two or three nights a week, for three years now, and can attest that it messes you up in many ways. You eat at odd hours, unless you cook and bring your food ahead of time its tough to eat healthy, you never have enough sleep (on my day off i sleep about 10 hours to make up for lost sleep), and i wonder if your immune system is compromised by the weird hours and how your body is always trying to adjust, especially when say, you do something with friends or loved ones on their off hours or off days.
Emotionally i think it takes a toll, too. If you work nights or overnights, you're the one who either can never meet friends or new people (who wants to get a drink at 10am?) and when you do hang out with friends, you're the one who has to leave early and can't drink and who can't really have as much fun as the others because at the back of your mind you're always counting how long it is until you have to leave for work. If you are in a relationship, or even just meet someone and try to be boyfriends with them, the odds are against you, unless of course, they work odd hours too. Also, since most workplaces have much fewer people working at night than during the day, you don't get as much human interaction with your co-workers so its tough to bond with them and also very hard to feel connected to your workplace, get the news, get the gossip, get the heads-up on what other positions may be opening, have a chance for higher up supervisors to see you and your work.
That being said, most everyone i know who works the midnight and night shifts has really good skin because they hardly ever see the sun. and we are able to go to the gym, the beach, shop, etc., early in the day, when all those places are far less crowded.
And yeah, i've asked my boss to consider moving me to a different sked.