I dont know but one thing my grandfather always told me. The more I keep doing these things the better I feel. He was perfectly healthy up until 8 days before he died. Healthy enough had come out and throw on a welding hood and weld on my derby cars, at 80. Dont quit it is good for ya. I'm a firm believer to this day it wasn't the cancer that killed him, it was they made him quit doing the things he wanted to do. Get out there and do what you enjoy bud