This goes beyond Boeing.
Way, way, way long ago (80s) I worked for another Elite Megacorp called IBM. It was on the cusp of some serious internal upheavals so various incentives (packages) were constantly rolling out. We were a diverse group age-wise, yet we all sat together at lunch.
The 50+ crowd would talk about their impending probable retirement and constantly bring up this 18 months study. It seemed every one of them had an anecdotal story of a buddy who retired and was dead in 6 months. The whole process was fraught with fear.
Flash forward 30 years. One of my 50+ co-workers who did retire around 55 back in 91 or so is still going just fine. He was the one who always brought up the "study." We met with him at lunch a few times shortly after he ER'd and he was a different, much happier person. I think he surprised himself!
So, yeah, this "study" is getting old. Both literally, and figuratively.
I recall first seeing this "study" perhaps 10 years ago when the info was circulated at a megacorp where I was doing part-time contract work. At about the same time, the same was shared on this forum.
Just now, I briefly tried to track it down to see when it originated, but found only one reference saying it has been on the Web for at least 20 years, which is about the time the Internet went mainstream.
The "report" by Dr. Sing Lin, which one can still find on the Web, is dated 2002. It referenced some data provided by a Dr. Ephrem (Siao Chung) Cheng which showed that Boeing retirees who hanged on till 65 definitely would not live another 18 months!
And Dr. Sing Lin went on to say that 65-year-old retirees at Lockheed, Bell Labs, Ford Motor, eerily shared the same fate. On the Web, I saw another source that "confirmed" the same phenomenon at Sandia Labs.
If I searched further, perhaps would see confirmation of the same experience in large foreign companies. Or is this only observed at American companies that exploited their employees and worked them to death?
Lastly, I used to see some writing from Boeing refuting this hoax. I cannot find it anymore, but recall that they said longevity of Boeing retirees showed no correlation to their age at retirement. A notable statistics they pointed out was that Boeing retirees had a longer lifespan than the general public.