Poor sleep patterns can be a contributing factor for erectile dysfunction, Mucher says. One review published in the journal Brain Research emphasized the intricate relationship between the level of sex hormones like testosterone, sexual function, and sleep, noting that testosterone levels increase with improved sleep, and lower levels are associated with sexual dysfunction. Hormone secretion is controlled by the body’s internal clock, and sleep patterns likely help the body determine when to release certain hormones.
4. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Erectile dysfunction (updated Nov 2015). https://www.niddk.nih.gov/health-information/health-topics/urologic-disease/erectile-dysfunction/Pages/facts.aspx (accessed Nov 2016). myDr myDr provides comprehensive Australian health and medical information, images and tools covering symptoms, diseases, tests, medicines and treatments, and nutrition and fitness.Related ArticlesImpotence causesFind out the physical and psychological causes of impotence, also called erectile dysfunction or ED.Erectile dysfunction: visiting your doctorFind out what questions a doctor may ask when discussing erectile dysfunction (ED, or impotence8 Surprising causes of erectile dysfunctionOccasional erectile dysfunction is not uncommon, but if it's persistent, erectile dysfunction caAdvertisement
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.
In some cases, nocturnal penile tumescence testing is performed to find out whether the man has erections while asleep. Healthy men usually have about four or five erections throughout the night. The man applies a device to the penis called a Rigiscan before going to bed at night, and the device can determine whether he has had erections. (If a man is able to have normal erections at night, this suggests a psychological cause for his impotence.)
Although vardenafil does not seem to produce significant clinical QT prolongation, it has been suggested that it be avoided in patients who have congenital QT prolongation abnormalities and in patients using class I antiarrhythmic drugs, such as quinidine and procainamide. It is also best to avoid the use of vardenafil with class III antiarrhythmic drugs, such as amiodarone or sotalol.
Among the phenomena in the ageing man are a decrease in erectile function and testosterone levels. Add to these, increased risk for CVD, muscle wasting, decrease in bone density and libido, with all of these factors having an interplay with testosterone metabolism.33 Androgens play a key role in maintaining erectile function through four main mechanisms. Androgen deprivation has been shown to result in impairment of NO synthase release, altered PDE5 expression and activity, impaired cavernosal nerve function, and contribution to veno-occlusive disease in the penis.34 The role of testosterone replacement therapy (TRT) as a potential to improve erectile function in the man with ED remains an issue for patient and physicians who are comfortable treating androgen deficiency which include primary care physicians and specialists. Androgens are known to have a significant impact on the function of the smooth musculature within the corpus spongiosum.35
The nerves and endothelium of sinusoids and vessels in the penis produce and release transmitters and modulators that control the contractile state of corporal smooth muscles. Although the membrane receptors play an important role, downstream signaling pathways are also important. The RhoA–Rho kinase pathway is involved in the regulation of cavernosal smooth muscle contraction. 
Instead of injecting a medicine, some men insert a suppository of alprostadil into the urethra. A suppository is a solid piece of medicine that you insert into your body where it dissolves. A health care professional will prescribe a prefilled applicator for you to insert the pellet about an inch into your urethra. An erection will begin within 8 to 10 minutes and may last 30 to 60 minutes.
The physical examination can reveal clues for physical causes of erectile dysfunction. A doctor will perform an assessment of BMI and waist circumference to evaluate for abdominal obesity. A genital examination is part of the evaluation of erectile dysfunction. The examination will focus on the penis and testes. The doctor will ask you about penile curvature and will examine the penis to see if there are any plaques (hard areas) palpable. The doctor will examine the testes to make sure they are in the proper location in the scrotum and are normal in size. Small testicles, lack of facial hair, and enlarged breasts (gynecomastia) can point to hormonal problems such as hypogonadism with low testosterone levels. A health care provider may check pulses in your groin and feet to determine if there is a suggestion of hardening of the arteries that could also affect the arteries to the penis.
ED usually has something physical behind it, particularly in older men. But psychological factors can be a factor in many cases of ED. Experts say stress, depression, poor self-esteem, and performance anxiety can short-circuit the process that leads to an erection. These factors can also make the problem worse in men whose ED stems from something physical.
Knowing about your history of ED will help your health provider learn if your problems are because of your desire for sex, erection function, ejaculation, or orgasm (climax). Some of these questions may seem private or even embarrassing. However, be assured that your doctor is a professional and your honest answers will help find the cause and best treatment for you.