My Husband Who Has Had MS For 15 Years With

My husband who has had MS for 15 years with very little disease progression has recently started smoking cigars almost if not daily. He was a cigarette smoker in his teens but stopped just before we met. He was 24 at the time. I am concerned about disease progression of MS and risk. He also had some issues with A fib back along. Should he continue this habit? I am concerned.he is 59 years old now.