You can, but it's gonna be weird =)
What we call a "vieux garçon" in french, is someone who is still not married after an advanced age. It means he's gonna end his life alone.
You can say :
Je suis une personne âgée (sound like "I'm an elder people")
But 68 isn't that old so you can just say :
Je suis un retraité de 68 ans
Which means "I'm a 68yo retired man."
Cheers !