Definition, Epidemiology, and Risk Factors of Erectile Dysfunction I. Definition and Epidemiology Erectile dysfunction (erectile dvsfunction (ED)) refers to the persistent inability of the penis to achieve and maintain an erection sufficient for satisfactory sexual intercourse in the past 3 months; ED is one of the most common sexual dysfunctions in men. Although ED is not a life-threatening disease, it is closely related to the patient’s quality of life, sexual partnership, and family stability, and is an early warning sign of many somatic diseases. The release of ED is not only affected by age, cardiovascular disease, diabetes and hyperlipidemia and other physical diseases, as well as sexual partnership, home conditions and other psychological and environmental factors, bad habits, drugs, surgery, race, culture, religion and socio-economic factors are also related to the occurrence of ED. Risk factors of ED (a) Age Current research suggests that age is the strongest independent factor among the risk factors related to ED. Kinsey’s study on the prevalence of ED in 1948 showed that ED is an age-related disease, with the prevalence rate ranging from 0.1% at the age of 20 to 75% at the age of 80. The results of the American MMAS in 1994 showed that the prevalence rate of ED was between 40-49, 50-59, 60-69 and 70%. ～In 1994, the results of MMAS in the United States showed that the prevalence of ED in the age groups of 40-49, 50-59, 60-69 and 70 years old and above were 38%, 48%, 57% and 67%, respectively. A randomized survey of 1,582 urban men over the age of 40 in Shanghai found that the prevalence of ED was 32.8% in the age group of 40-49, 36.4% in the age group of 50-59, 74.2% in the age group of 60-69, and 86.3% in the age group of 70 years or older. Studies have also shown that the association between age and ED is not only in terms of increased prevalence, but also in terms of changes in severity, with moderate to higher levels of ED being more common in older men over the age of 60. It is generally believed that a significant decrease in serum androgen levels with increasing age may be the direct cause [6]. However, there have been no findings to demonstrate a significant relationship between decreased serum free testosterone and ED. In addition, with increasing age, the structure of the tunica albuginea and corpus cavernosum of the penis changes, which may lead to a decrease in the ability to block venous blood return; the increasing prevalence of cardiovascular and cerebral vascular diseases, hypertension and diabetes mellitus, as well as the treatment of these diseases, have all impaired the erectile function of the penis to varying degrees, and this tendency has also increased with age. (ii) Somatic diseases 1, cardiovascular diseases Cardiovascular diseases are the main somatic diseases associated with ED, including atherosclerosis, peripheral vascular disease, hypertension and myocardial infarction. Cardiovascular disease leads to arterial ED by affecting the blood supply to the cavernous body. 59% of patients over the age of 60 who had suffered from ischemic heart disease had a prevalence of ED, compared with 35% of healthy people of the same age. In the MMAS, after correcting for age, the prevalence of complete ED was 39% in respondents who had been treated for heart disease; the prevalence of ED in the untreated hypertensive population was 15%, compared with 9,6% in the overall population. Some studies have also found that ED may be the first manifestation or “warning sign” of cardiovascular disease. Diabetes can affect erectile function by affecting the autonomic nervous system, peripheral vascular system and psychoneurological system. In the MMAS, age-corrected results showed that the prevalence of full-blown ED was three times higher in diabetic patients than in nondiabetic controls (68 years of ED per 1,000 diabetic patients). The likelihood of ED occurring within 10 years in those diagnosed with diabetes was 50%. The severity and prevalence of ED was significantly correlated with age and duration of diabetes, type of diabetes, glycemic control, diabetic neuropathy, diabetic nephropathy, and hypertension. 3, Abnormal lipid metabolism The role of hypercholesterolemia in sexual dysfunction is controversial. A study showed that men with total cholesterol (TC) greater than 240mq/dl (6, 2mmol/L) had a 1, 83 times higher risk of ED than men with TC less than 180mq/dl (4, 65mmol/L). In MMAS, high-density lipoprotein (HDL) is negatively correlated with ED patients. 4, Chronic prostatitis Some patients with chronic prostatitis have symptoms such as premature ejaculation, decreased libido, erectile dysfunction and painful ejaculation. The mechanism by which chronic prostatitis leads to sexual dysfunction is unknown, and most scholars believe that anxiety, depression, low self-esteem, loss of energy, fatigue, paranoia and insomnia are the main causes. The recurrence of testicular swelling and pain, perineal and penile discomfort, and lower urinary tract symptoms also aggravate the patient’s psychological burden. As the sexual dysfunction of the majority of chronic prostatitis patients is caused by psychological factors, in addition to medication, more psychological counseling and treatment is also needed. 5, chronic hepatic and renal insufficiency The prevalence of ED in patients with alcoholic cirrhosis is 70%, while in patients with non-alcoholic cirrhosis is 25%, suggesting that the prevalence of ED is related to hepatic insufficiency. The prevalence of ED in patients with chronic renal insufficiency is as high as 45%, but the pathophysiologic mechanism is not known.Cerqueira’s study of patients on chronic dialysis found that 58% of patients had ED, of which 28.6% were severe, 15.1% were moderate, and 14.3% were mild. Another study pointed out that, for kidney transplant recipients, if the transplanted kidney function is normal, most of the patients can return to the level of sexual function before the disease. (iii) Drugs Some anti-hypertensive drugs play an important role in the development of ED, MMAS, and the treatment of cardiac drugs related to ED accounted for about 28% of the reports; other drugs, such as hypoglycemic drugs and tricyclic antidepressants can also lead to ED. Cardioactive drugs: long-term use of cardiac glycosides can lead to ED, along with gynecomastia and libido, the mechanism of which is not known, but the serum level of estrogen increased, luteinizing hormone, and the serum level of luteinizing hormone increased, and the serum level of luteinizing hormone increased. The mechanism is unknown, but elevated serum estrogen levels and decreased luteinizing hormone (LH) and testosterone levels may play a role. In recent years, it has been found that digoxin may cause ED by inhibiting the action of sodium/potassium ATPase. Hormones: Estrogens and luteinizing hormone-releasing hormone (LHRH) analogs used in the treatment of prostate cancer often lead to ED. exogenous estrogens may inhibit gonadotropin-releasing hormone secretion, which leads to a decrease in testosterone levels in the blood. The use of LHRH analogs can also reduce libido in 92% of patients and cause ED in 86%. Psychotropic medications: Most medications that can produce central nervous system sedation or depression can cause ED. Reasons for this may include elevation of serum prolactin, sedative effects, anticholinergic effects, reduction of the activity of the dopamine system, and central effects on the limbic system. （Lifestyle habits related to ED include long-term smoking, alcoholism and drug abuse. 1, smoking Epidemiologic investigation that smoking can lead to ED, some people believe that smoking can increase the possibility of ED. However, it is certain that smoking is associated with ED by increasing the prevalence of cardiovascular disease. the MMAS study showed that baseline levels of smoking were twice as high in moderate or severe ED as in the control group (24% vs. 14%). In patients being treated for heart disease, the age-corrected prevalence of complete ED was 56% in smokers versus 21% in nonsmokers; in patients being treated for hypertension, the prevalence of complete ED was significantly higher in smokers than in nonsmokers (20% vs. 8.5%); in addition, smoking may exacerbate the effects of medications on ED. In a survey of sexual function in 50 patients admitted to the hospital for alcoholism, the prevalence of ED was 54% in alcoholics compared with 28% in controls (P < 0.05), compared with the general population matched for age and social relations. In another study evaluating sexual dysfunction in male and female alcoholics, 63% of male alcoholics had sexual dysfunction, mainly in the form of erectile and libido disorders, compared with 10% of controls who were matched for age. (v) Living status Divorced, living alone, or ? The prevalence of ED was higher in those living alone than in those with a spouse.Johannes concluded that education plays a positive role in erectile function. After correcting for age, the prevalence of ED was lower in those with a college degree or higher than in those with a high school degree or less. The prevalence of ED was lower among high income earners than low income earners, Ansong believes that the above phenomenon may be due to the fact that low education level and low income earners are often accompanied by a lack of attention to their health, as well as poor living conditions, while smokers and alcoholics tend to be more frequent. (vi) Trauma and medical factors ED is associated with pelvic surgery, especially radical prostatectomy, cystectomy, and rectal surgery. In radical prostatectomy, the use of nerve preservation can significantly improve postoperative erectile function, but still more than 50% of patients need to seek other forms of treatment to improve their erectile function after surgery; patients with symptoms of lower urinary tract obstruction are also associated with a higher prevalence of ED; genital, pelvic, and spinal cord injuries can disrupt nerves and blood vessels that are distributed to the penis, which is also a risk factor for ED; spinal cord The severity of ED due to spinal cord injury is determined by the segment of the injury, the presence of spinal shock, and the degree of trauma; the prevalence of ED in people with spinal cord injury is 64% to 94%. The incidence of ED is higher in prostate cancer patients treated with radiation than in patients undergoing radical prostatectomy with nerve preservation.