Once again, all the information I can find suggesting this is from anti-Scientology sites. Obviously, official Church sites deny this. I will abide by this affidavit from L. Ron Hubbard filed in June 1983. It was good enough for the State of California.
Also, I found a quote from one of the workers on his ranch in the 1980's.
“Mr. Hubbard was very active until the last time I saw him which was just a matter of days before he passed on. That was why it came as such a surprise to me for he appeared normal and certainly not suffering from any physical or mental ailment. He had been alert, chipper, active and content.”
Affidavit from L. Ron Hubbard