4. EPIDEMIOLOGY AND PREVALENCE OF SEXUAL DYSFUNCTION AND DISORDERS OF MALE REPRODUCTIVE HEALTH
4.1. Erectile dysfunction
Epidemiological data have shown a high prevalence and incidence of ED worldwide [208]. Among others, the Massachusetts Male Aging Study (MMAS) [209] reported an overall prevalence of 52% ED in non-institutionalised men aged 40-70 years in the Boston area; specific prevalence for minimal, moderate, and complete ED was 17.2%, 25.2%, and 9.6%, respectively. In the Cologne study of men aged 30-80 years, the prevalence of ED was 19.2%, with a steep age-related increase from 2.3% to 53.4% [210]. The incidence rate of ED (new cases per 1,000 men annually) was 26 in the long-term data from the MMAS study [211] and 19.2 (mean follow-up of 4.2 years) in a Dutch study [212]. In a cross-sectional real-life study among men seeking first medical help for new-onset ED, one in four patients was younger than 40 years, with almost 50% of the young men complaining of severe ED [213]. Differences among these studies can be explained by differences in methodology, ages, and socio-economic and cultural status of the populations studied. The prevalence rates of ED studies are reported in Table 1 online supplementary evidence: https://uroweb.org/guidelines/sexual-and-reproductive-health/publications-appendices.
4.2. Premature ejaculation
As evidenced by the highly discrepant prevalence rates reported in Table 2 online supplementary evidence (https://uroweb.org/guidelines/sexual-and-reproductive-health/publications-appendices) the method of recruitment for study participation, method of data collection and operational criteria can all greatly affect reported prevalence rates of premature ejaculation (PE) [214]. The major problem in assessing the prevalence of PE was the lack of a universally recognised definition at the time the surveys were conducted [215]. Vague definitions without specific operational criteria, different manners of sampling, and non-standardised data acquisition have led over time to heterogeneity in estimated prevalence [215-219]. The highest prevalence rate of 31% (men aged 18-59 years) was found by the National Health and Social Life Survey (NHSLS), which determines adult sexual behaviour in the USA [220]. Prevalence rates were 30% (18-29 years), 32% (30-39 years), 28% (40-49 years) and 55% (50-59 years), respectively. It is, however, unlikely that the PE prevalence is as high as 20-30% based on the relatively low number of men who seek medical help for PE. These high prevalence rates may be a result of the dichotomous scale (yes/no) in a single question asking if ejaculation occurred too early, as the prevalence rates in European studies have been significantly lower [221]. Two separate observational, cross-sectional surveys from different continents found that overall prevalence of PE was 19.8 and 25.8%, respectively [222,223]. Further stratifying these complaints into the classifications defined by Waldinger et al., [224], rates of lifelong PE were 2.3 and 3.18%, acquired PE 3.9 and 4.48%, variable PE 8.5 and 11.38% and subjective PE 5.1 and 6.4%, respectively [222,223]. Both studies showed that men with acquired PE were more likely to seek treatment compared to men with lifelong PE. Treatment-seeking behaviour may have contributed to errors in the previously reported rates of PE, as it is possible that men with lifelong PE came to terms with their problem and did not seek treatment. The additional psychological burden of a new change in ejaculatory latency in acquired PE may have prompted more frequent treatment seeking [225]. Thus, it is likely that there is disparity between the incidence of the various PE sub-types in the general community and in men actively seeking treatment for PE [226,227]. This disparity could be a further barrier to understanding the true incidence of each sub-type of PE. An approximately 5% prevalence of acquired PE and lifelong PE in the general population is consistent with epidemiological data indicating that around 5% of the population have an ejaculation latency of < 2 minutes [228].
4.3. Other ejaculatory disorders
4.3.1. Delayed ejaculation
Due to its rarity and uncertain definitions, the epidemiology of delayed ejaculation (DE) is not clear [229]. However, several well-designed epidemiological studies have revealed that its prevalence is around 3% among sexually active men [220,230]. According to data from the NHSLS, 7.78% of a national probability sample of 1,246 men aged 18-59 years reported inability achieving climax or ejaculation [220]. In a similar stratified national probability sample survey completed over 6 months among 11,161 men and women aged 16-44 years in Britain, 0.7% of men reported inability to reach orgasm [231]. In an international survey of sexual problems among 13,618 men aged 40–80 years from 29 countries, 1.1-2.8% of men reported that they frequently experience inability to reach orgasm [232]. Another study conducted in the United States (USA), in a national probability sample of 1,455 men aged 57-85 years, 20% of men reported inability to climax and 73% reported that they were bothered by this problem. [233]. Considering the findings of these epidemiological studies and their clinical experiences, some urologists and sex therapists have postulated that the prevalence of DE may be higher among older men [234-236]. Similar to the general population, the prevalence of men with DE is low among patients who seek treatment for their sexual problems. An Indian study that evaluated the data on 1,000 consecutive patients with sexual disorders who attended a psychosexual clinic demonstrated that the prevalence of DE was 0.6% and it was more frequent in elderly people with diabetes [237]. Nazareth et al., [238] evaluated the prevalence of International Classification of Diseases 10th edition (ICD-10) diagnosed sexual dysfunctions among 447 men attending 13 general practices in London, UK and found that 2.5% of the men reported inhibited orgasm during intercourse. Similar to PE, there are distinctions among lifelong, acquired and situational DE [239]. Although the evidence is limited, the prevalence of lifelong and acquired DE is estimated at 1 and 4%, respectively [240].
4.3.2. Anejaculation and Anorgasmia
Establishing the exact prevalence of anejaculation and anorgasmia is difficult since many men cannot distinguish between ejaculation and orgasm. The rarity of these clinical conditions further hampers the attempts to conduct epidemiological studies. In a report from the USA, 8% of men reported unsuccessfully achieving orgasm during the past year [220].
According to Kinsey et al., [241], 0.14% of the general population have anejaculation. The most common causes of anejaculation were spinal cord injury, diabetes mellitus and multiple sclerosis. Especially in most cases of spinal cord injury, medical assistance is the only way to ejaculate. While masturbation leads to the lowest rates of ejaculation, higher response rates can be obtained with penile vibratory stimulation or acetylcholine esterase inhibitors followed by masturbation in patients with spinal cord injury [242].
4.3.3. Retrograde ejaculation
Similarly to anejaculation, it is difficult to estimate the true incidence of retrograde ejaculation (RE). Although RE is generally reported in 0.3-2% of patients attending fertility clinics [243], diabetes may increase these rates by leading to autonomic neuropathy. Autonomic neuropathy results in ED and ejaculatory dysfunctions ranging from DE to RE and anejaculation, depending on the degree of sympathetic autonomic neuropathy involved [244]. In 54 diabetic patients with sexual dysfunction, RE was observed with a 6% incidence [245]. In a controlled trial, RE was observed in 34.6% of diabetic men [246]. A more recent trial reported the rate of RE among 57 type-1-diabetes mellitus patients (aged 18-50 years) was at least 8.8% [247]. Retrograde ejaculation was also reported in studies of patients who had undergone transurethral resection of prostate (TURP) or open prostatectomy due to disrupted bladder neck integrity. A study of the effect of prostatectomy on QoL in 5,276 men after TURP, found that 68% reported post-surgical RE [248]. However, with the development of less invasive techniques, the incidence of RE decreases following the surgical treatment of LUTS [249-253]. There is a relative heterogeneity of surgical treatment modalities for RE although the scientific literature does not provide detailed and homogenous data on the objective prevalence of post-surgical RE, and the Guidelines Panel cannot make a specific recommendation in this regard.
4.3.4. Painful ejaculation
Painful ejaculation is a common but poorly understood clinical phenomenon, which is associated with sexual dysfunction. Several studies demonstrated its prevalence to range between 1-10% in the general population [254-256]; however, it may increase to 30-75% among men with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) [257-261]. It should be noted that the design of most of these studies was not scientifically sound and the condition was probably under-reported due to the lack of an evidence-based definition and well-defined prognostic criteria.
4.3.5. Haemospermia
The exact incidence and prevalence of haemospermia are difficult to elucidate due to a number of factors including its covert presentation, usually self-limiting nature and patient embarrassment. The symptoms represent 1-1.5% of all urological referrals and occurs in all age groups, with a mean age of 37 years [262,263]. In a PCa screening study of 26,126 men, aged > 50 years or older than 40 with a history of PCa or of black ethnicity, haemospermia was found in 0.5% on entry to the trial [264].
4.4. Low sexual desire
The global prevalence of low sexual desire in men is 3-28% [232,265,266]. Low solitary and dyadic sexual desires have been reported in 68% and 14% of men, respectively [267]. Also, low sexual desire has been observed as a common complaint in gay men, with a prevalence of 19-57% [268,269]. Despite its relationship with age, low sexual desire has also been reported among young men (18-29 years), with a prevalence of 6-19% [220,270,271].