How do I persuade my father to stop taking statins?

4 years ago my father took a routine trip to the doctors, (then aged 74), and was prescribed statins and a whole bunch of other drugs. He previously had no history of heart or cholesterol problems. Since then he has steadily deteriorated mentally to the extent that he has been tested for alzheimers and dementia, both of which he has been cleared of. My belief is that the drugs are causing this but I can't persuade him to try leaving off of them for a while. Despite an otherwise clean bill of health, the Doctors would have him believe that he will suffer a heart attack or stroke if he stops. Any suggestions. No jokes please