Sex Drive for middle aged men?

Scott K asked:


I am 49 years old. I am not gay, I love women and I often fantisize about women that I see that I think are attractive, but when it comes right down to the act itself i suddenly loose interest. Everything works just fine, I mean i could cut diamonds with some of the erections I get but it seems my sex drive has really gone down. Is that natural in men my age?