Age
Just because you get older does not necessarily mean you will suffer from ED, but the risk is greater with age. With increased years, most men become more dependent on direct stimulation of the penis and surrounding regions in order to get an erection. One’s imagination, thought, or other sensory input that was sufficient in the past, may not be sufficient anymore.
Mood also becomes more important as fatigue, stress, depression, or frustration can hamper the ability to achieve an erection. The time from release to a new erection also tends to increase with age. Sometimes, it can take up to a week before an erection can be obtained again after sex.
