Here’s a new word for you: obsolagnium. You may not find it in an ordinary dictionary. But if you are over 50, you may well be familiar with the concept, because it means “waning sexual desire resulting from age.”

In fact, it is rarely age per se that accounts for declines in libido among those in the second half-century of life. Rather, it can be any of a dozen or more factors more common in older people that account for the changes. Many of these factors are subject to modification that can restore, if not the sexual energy of youth, at least the desire to seek and the ability to enjoy sex.

Nor is it just hormones. Addressing only the distaff half of the population, the Boston Women’s Health Book Collective, in its newest work, “Our Bodies, Ourselves: Menopause,” points out: “Our sexual desire and satisfaction may be influenced by our life circumstances, including the quality of our sexual relationships, our emotional and physical health, and our values and thoughts about sexuality, as well as by the aging process and the shifting hormone levels that occur during the menopause transition.”

The same, of course, is true of men. Difficult life circumstances can do much to dampen anyone’s libido. Stress at work or home, looming bankruptcy, impending divorce, serious illness, depression, a history of sexual abuse and a host of medications are among the many things that can put a big crimp in your desire for sex at any age.