"There have been plenty of detailed studies carried out recently... that demonstrate how the life expectancy of a retiree drops the earlier they reitre."

The main finding of the study you link to seems to be that early retirement doesn't increase life expectancy, as some have previously assumed.

It did find that "employees who retired at 55 had a significantly increased mortality compared with those who retired at 65", but with the proviso that "poorer health status of some early retirees may play some part".