Long term use of statin drugs can/will deteriorate muscles, much like Atkins diet if you have lost all of the fat and there is nothing but muscles left in the body to burn without intake of carbos or fat. My uncle Jim has been on Lipitor for 15 years or more and has had a noticable loss of strength, enough that my Mom and her 2 sisters, all nurses, will not take it any statin drug at all (70 to 80 yr old).
You’re going to lose muscle, pretty much no matter what, over a period of 15 years, and especially from 70 to 80 years old. I believe even Jack LaLane is a smaller man that he was 15 years ago.