Estimates say that up to a fifth of heterosexual couples have anal intercourse at least intermittently, more rarely exclusively.
The risk of sexually transmitted infections is the same or perhaps higher with anal than with vaginal penetration. There's more likelihood of trauma, since anal intercourse requires complete relaxation of the rectal sphincter muscles before penetration. Trauma or injury to those muscles can lead to loss of muscle tone or control. That makes this form of intimacy not entirely "safe," but, more importantly, consent freely given by both partners is an essential feature of sexual activity in a loving relationship.
You asked whether this was a new phenomenon and whether you were "too old" to adapt! I don’t think it's new (or, at less than 20 percent, a phenomenon), but our notions about sexuality and what's "typical" or even erotic are very complicated and influenced by many factors. You may never become comfortable with this form of intimacy, but you are never too old to explore options and be open to new sexual techniques.