Its natural for men to notice a gradual decrease in sex drive (libido) as they age. The degree of this decline varies, but most men maintain at least some amount of sexual interest into their 60s and 70s. After the age of 40, a natural fall in testosterone levels can lead to a loss of libido in men and an increase in the time needed to achieve an erection. Testosterone levels peak in the late teens, and the initial drop does not usually have any significant physical effects before the age of 30. Between the ages of 30 and 40, a man’s testosterone levels fall by about 1% every year, while high enough to be measured, the effects are rarely a concern. After the age of 40, however, a low libido in men can be noticeable as testosterone levels decrease even further. Other factors that can contribute to a loss of sex drive include depression, stress, alcoholism, illicit drug use, fatigue, medication side effects, and relationship problems. However, it's important to note that loss of sex drive is not inevitable with age, and there are steps men can take to maintain their sexual health, such as regular exercise, a healthy diet, and managing stress.