My dad is 78 years old. He has always been a hairy man especially on his chest. The next time I went to visit them in fla he had absolutely no chest hair. What could cause a man to loose his chest hair and alot of it?
Kidding aside, he could also have an autoimmune disorder (there are many) which causes alopecia (hair loss) in patches or generalized. If he is losing hair elsewhere, that is likely. A dermatologist could be consulted if it bothers him or he has other symptoms of autoimmune problems. You could research causes of alopecia to see if anything seems to fit.