I have often heard this. And even witnessed it some. But i wonder if the phenomenon is actually due to the fact that people who are in good health and well when they retire are more likely to stay active and those who are not in good health or don't feel well, tend to not stay very busy after they no longer are required to.

My father noticed the same thing and feared it would happen to him, so he kept working part time after retirement. When he finally retired completely, he died within a few years at a healthy (other than sudden cancer) age of 74. I’ve suspected there is something about the pressure of work that “holds” us together, though I can’t put my finger on it.