There was a lot of curious phrasing in the article and is very unclear. It starts off with the line "those who tend to stay up late and sleep in well past sunrise are at increased risk of early death". But then goes on to talk about the health consequences of Night Hawks trying to live as Morning Larks.

So the article is saying don't sleep in or you'll die young but if you get up early your health will suffer adversely?

Also seems to hinge on whether the participants "consider themselves" to be a night-owl. If the effect is there, you should be able to stratify by, say, regularly going to bed after 1am (or whatever). This doesn't seem to be that.