I would think the 25% is just an average. Some men never have a problem with erections. Some healthy men in their 60's never have a problem with their erections -- no Viagra needed at all, thank you. And, no, it is NOT completely associated with age. In fact, many men in their 40's and even younger, are already dealing with ED, especially if they smoke, are obese, don't exercise, or are addicted to porn, among other things. In fact, even men in their 20's and 30's can have these problems.
Ginseng, specifically “red ginseng,” is known as the “herbal Viagra” that helps puts to rest men’s bedroom woes. Red ginseng is when the root has been steamed and then dried. The ginseng root is the part of the plant that is mostly used as a natural remedy when in its supplement form. However, the plant must be grown for a minimum of five years before it can be used. In a 2008 review, seven studies on red ginseng and ED, ranging in dosages from 600 to 1,000 milligrams three times a day, were found to provide evidence for the effectiveness of the herb in ED treatment.
Something else to consider is your porn use. If you are masturbating to very stimulating porn on a regular basis then it might be difficult to get as aroused in the bedroom with your partner. Watching video pornography is very stimulating and often men have difficulty creating that same level of arousal or stimulation with their partners. Consider masturbating without technology as visual images in your head are less stimulating then watching something live. Try this for two weeks and see if your erection quality improves.
Exercise regularly. Make it a priority to get outside or go to the gym to walk, run, swim, bike, or do strength training at least 4 times a week. According to a study conducted by Harvard, walking 30 minutes a day caused a 41% drop in risk for ED. Getting regular exercise aids circulation, getting your blood pumping through your entire body. When it's time to sustain an erection, better circulation is key.
ED exists in approximately 75% of men with SB and is dependent upon the level of the neurologic lesion (54). The level of the neurologic lesions usually corresponds to sensation and penile sensation indicates pudendal nerve signaling. With absent sacral reflexes ED is variable. Furthermore, Diamond et al. reported that 64% of men with lesions below T10 obtained erections versus 14% with a lesion above T10 (55). It has also been suggested that ED may be underreported due to lack of sexual education even in men without associated cognitive impairment (56).
A physical exam checks your total health. Examination focusing on your genitals (penis and testicles) is often done to check for ED. Based on your age and risk factors, the exam may also focus on your heart and blood system: heart, peripheral pulses and blood pressure. Based on your age and family history your doctor may do a rectal exam to check the prostate. These tests are not painful. Most patients do not need a lot of testing before starting treatment.