The rate at which aging affects internal organs varies from person to person; one fifty-year-old man may be much stronger than another fifty-year-old man. However, most people's systems slow down as they age, and with some exceptions, even the virile and athletic fifty-year-old man is probably not at the same level of health as when her was thirty years old. So in this sense, he is more prone to experiencing heartburn.
Diminished muscle tone and slackening physical abilities affect the digestive system, too, which is anther reason why GERD is more prevalent among middle-aged and older people.