Introduction

Erectile dysfunction (ED) is usually defined as the persistent inability to attain or maintain penile erection sufficient for sexual intercourse.¹ The reported prevalence of ED has differed from country to country. For example, ED prevalence in the USA, UK, Japan, Denmark, and Australia was reported to be 52, 32, 26, 32, and 34%, respectively.^2,3,4 These different rates of prevalence may be due to not only ethnic differences, but may also be due to different definitions of ED, subjects, and research methods.⁵ One study reported that despite a high prevalence of sexual problems in primary care patients, only a small percent of these problems were detected.⁶ Therefore, an accurate survey of prevalence and risk factors for ED in the primary care setting is very important because such survey results can provide physicians with fundamental guidelines on sexual counselling in clinical practice. Recently, a five-item version of the International Index of Erectile Function (IIEF-5), which is a useful instrument for the detection of ED in clinical settings, was developed⁷ and a validation study was carried out on the Korean version of the IIEF-5.⁸ In this study, we investigated the prevalence of ED and the associated factors related to ED among male patients in family practices in Korea by using the Korean version of the IIEF-5.

Materials and methods

Study subjects

Subjects were enrolled consecutively by 32 family physicians of hospital-based family practices in Korea from November 1 to December 15, 1999. Selection criteria included male patients aged 20 y and older visiting the investigating physicians. Patients who had difficulty in understanding and writing the questionnaire were excluded. Each subject for this survey was informed and consented to participate.

Questionnaire

Using a structured, self-administered questionnaire, patients were asked about their erectile function, demographic characteristics, and lifestyle. The Korean version of the IIEF-5, which has been verified in terms of validity and reliability, was used for the assessment of ED.⁸ It consists of five questions in two domains, including four questions on erectile function and one question on intercourse satisfaction. Each item is scored on a five-point ordinal scale (1–5) where lower values represent poorer sexual function.^7,8 A response of one for a question was considered the least functional, whereas a response of five was considered the most functional. In our previous study, ED was classified into the following four categories based on the Korean version of the IIEF-5 scores: severe (5–9), moderate (10–13), mild (14–17), and normal (18–25).⁸ Thus, we defined ED as a score of 17 or less on the Korean version of the IIEF-5. Questions about demographic characteristics and lifestyle consisted of marital status, educational status, income, alcohol drinking, cigarette smoking, and exercise.

Data collection and analysis

The investigating physicians checked concurrent illnesses and measured body mass index (weight divided by height squared; kg/m²). Physicians also completed standardized case record forms. Each completed questionnaire and case records form was sent to a coordinating center of the Korea Post-Marketing Surveillance Research Group. Using statistical analysis, prevalence estimates for the total population of men aged 20 y and older were age standardized (direct standardization) to the current male population of Korea (population data as of July 1, 2000). The data were analyzed using SAS software, version 8.02 for Windows. We used the Mantel–Haenzel test, Pearson's ² test, and unconditional logistic regression, as appropriate, to investigate the factors associated with ED.

Results

Characteristics of study subjects

Of the 3593 subjects in the study, 3501 (97.4%) completed the structured, self-administered questionnaire. Table 1 shows selected characteristics of the study subjects. The mean age (standard deviation) of men in our study was 40.6 (11.5) y. More than 50% of the participating men had been smoking more than 10 pack-years. One-third had been exercising regularly, about 50% were college graduates, about two-thirds had light activity related to job, about 90% were married, and about two-thirds were overweight (BMI25 kg/m² or more). Hypertension was the most common chronic disease (20.7%) in study subjects, followed by gastritis and peptic ulcer disease (19.7%), diabetes (11.3%), chronic liver disease (7.1%), hyperlipidemia (3.2%), anxiety (2.3%), depression (2.3%), heart disease (1.8%), prostatic hyperplasia (1.3%), and chronic obstructive lung disease (1.3%).

Table 1 - Baseline characteristics of 3501 study subjects.

Full table

Prevalence of ED

The overall crude prevalence of ED was 36.6% (95% CI 35.0–38.2); the frequency of mild, moderate, and severe dysfunction was 24.7, 10.2, and 1.6%, respectively (Figure 1). After direct standardization to the Korean population as of the year 2000, we estimated the age-adjusted prevalence of ED among Korean men to be 32.2% (95% CI 30.6–33.7). The prevalence and severity of ED increased with age (P<0.001). The prevalence of ED was 14.4% for ages 20–29 y, 21.2% for ages 30–39 y, 32.5% for ages 40–49 y, 52.4% for ages 50–59 y, and 68.5% for ages60 y, respectively.

Figure 1.

Prevalence and severity of ED by age (N=3501).

Full figure and legend (71K)

Factors associated with ED

Table 2 shows the association between ED and possible risk factors according to prevalence odds ratios. Heavy smoking of more than 30 pack-years (OR 1.36, 95% CI 1.00–1.86) was associated with an increased risk of ED. Compared with men having less than 12 years education, the adjusted odds ratios (OR) for ED for men with education of 12 y and greater than 12 y were 0.69 (95% CI 0.50–0.96) and 0.56 (95% CI 0.40–0.79), respectively. Compared with men having light job-related physical activity, the adjusted OR for ED for those with high job-related physical activity was 1.65 (95% CI 1.16–2.34). Low income was significantly associated with ED (P<0.001). In this study, other risk factors such as alcohol consumption, exercise, marital status, and obesity were not found to be associated with an increased risk of ED.

Table 2 - Prevalence OR of potential risk factors for ED in 3501 men.

Full table

After adjusting for age, smoking amount, educational status, job-related physical activity, and income level, we analyzed the association between ED and concurrent diseases (Table 3). ED was significantly associated with diabetes (OR 1.49, 95% CI 1.12–1.98), anxiety (OR 3.01, 95% CI 1.62–5.56), and depression (OR 3.61, 95% CI 1.84–7.08). Other medical conditions such as hypertension, benign prostatic hyperplasia, cardiovascular disease, chronic liver disease, chronic obstructive lung disease, gastritis and peptic ulcer, and hyperlipidemia were not associated with ED in this study.

Table 3 - Prevalence OR of selected diseases for ED in 3501 men.

Full table

Discussion

This study shows that the prevalence of ED in primary care was determined to be 36.6%. Risk factors and concurrent diseases associated with ED were increasing age, more than 30 pack-years of smoking, low educational status, low income level, high degree of job-related physical activity, diabetes, depression, and anxiety. This is the first study to investigate the prevalence of ED in Korea using the Korean version of IIEF-5 and one of the few studies in the primary care setting.

At present, five types of sexual function questionnaire are available; the more popular being a brief male sexual function inventory for urology⁹ and IIEF.¹⁰ The latter has been newly developed and established. It was designed to diagnose ED reliably, to be a self-administered measure of ED, and to monitor changes related to treatment.¹⁰ Its Korean version was established to be a reliable, validated, multidimensional scale for the assessment of ED.^11,12

In this study, ED was evaluated by the Korean version of the IIEF-5. The IIEF-5 was developed to be used as a simple diagnostic tool for ED in general practice settings.⁷ The Korean version of the IIEF-5 was also established as a reliable, validated scale for assessment of ED, and its cutoff score has been defined.⁸

In our study, the overall prevalence of ED was 36.6%. This result is similar to that (39.4%) of an Australian outpatient-based study of subjects between the ages of 18 and 91 y.¹³ However, it is lower than that (58.9%) from a community-based study in Chungup county, Chonbuk province, Korea.¹⁴ This is due to the difference in the age distribution and difference in the assessment questionnaire for ED. The prevalence of ED varied according to age; 14.4% in the third decade, 21.2% in the fourth, 32.5% in the fifth, 52.4% in the sixth, and 68.5% in the seventh and above. The prevalence and severity of ED increased especially rapidly with increasing age after 40 old. This result is similar to results of previous studies in other countries^15,16,17 and suggests that age is an evident risk factor for ED.

Our study showed an association between cigarette smoking and the risk of ED, consistent with other studies.^18,19 A smoking history more than 30 pack-years was a strong predictor of ED. This information may motivate smokers to quit. Alcohol consumption and exercise were not associated with ED, consistent with other studies.²⁰

We investigated an association between socioeconomic status and ED. Education was inversely related to ED in this study, consistent with other studies.^17,21 Heavy job-related activity was also associated with ED as in another study, which found blue-collar occupation to be a risk factor for ED.²⁰ Low income was associated with ED, which was inconsistent with other studies.^20,21 Our results suggest that men of lower socioeconomic status are more likely to incur ED. Marital status was not associated with ED, consistent with another study.¹⁷ Obesity (BMI >27 kg/m²) was not a risk factor for ED, which was consistent with some,¹⁵ but not all studies.²⁰

Many studies have shown ED to be more prevalent in patients with diabetes.^16,17,20,21 We also found that diabetic patients had high rates (55%) of ED and having diabetes was associated with a 1.5-fold increase in the risk of ED. Depression and anxiety were associated with ED, but this is controversial.^15,17,20 Hypertension and heart disease were not associated with ED in this study, unlike other studies.^17,20,21,22 This is due to the difference in the severity of diseases among study populations. We also included patients with untreated or mild hypertension that was not associated with ED²¹ in this study. This would produce an overall OR of null. Hyperlipidemia was not associated with ED in this study, a finding inconsistent with other studies.^22,23 Hyperlipidemia is frequently asymptomatic or underdiagnosed, which would likely result in nondifferential misclassification of the results toward null. The prevalence of benign prostatic hyperplasia was quite low in this study compared with another study.²⁴ This may be due to the small proportion of elderly subjects and to underdiagnosis of prostatic hyperplasia in this study. Benign prostatic hyperplasia was not associated with ED in this study, a finding inconsistent with other studies.^23,25 This conflicting result may be due to similar reasons as the reasons for the low prevalence of prostatic hyperplasia. Further studies are required to determine the reasons for these conflicting results.

A possible problem of external validity of this study may be that our study subjects were recruited from hospital-based family practice clinics. Our results may not accurately represent the prevalence of ED in the Korean male population. Therefore, we estimated age-adjusted prevalence by direct standardization. However, in our Korean medical environment, patients seen in hospital- and community-based family practice settings are not differentiated. Patients are able to seek care at family practice clinics of secondary and tertiary medical centers without referrals and their medical insurance reimbursement is not penalized for doing so. Thus, our study subjects do represent the general population in primary care in Korea and we consider the behavior of ED patients in our study to be applicable to other general primary care settings. This study was planned as a sequential survey to avoid subject selection bias, but such bias could not be completely eliminated due to clinical settings. Some of the elderly and severely ill patients were rejected. If they had been enrolled, the prevalence of ED would have been higher.

In summary, ED is a major health problem among Korean men in the primary care setting. Risk factors associated with ED are age, more than 30 pack-years of smoking, low¹³ educational status, low income level, and a high degree of job-related physical activity. Diabetes, depression, and anxiety are frequently associated with ED.

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Acknowledgements

This study is an add-on study of postmarketing surveillance for Sildenafil, which is supported by a grant from Pfizer Korea.