A fairly surprising claim...
Also since I enjoy discussing the meat behind brief and shallow articles here is the link for the paper they're discussing.http://www.iea.org.uk/sites/default/files/in-the-media/files/Work%20Longer,%20Live_Healthier.pdf
...I think Jamesqf is on the right track, though maybe not necessarily about work, maybe just activity. If you stay active, then you'll be better off. If you retire and become inactive, then you'll be worse off.
What I do believe is that sitting around doing nothing, never getting out of the house, having no goals, and not contributing to society in any way IS bad for your health!