Age-related prevalence of erectile dysfunction in Japan: Assessment by the International Index of Erectile Function

Authors


Correspondence: Ken Marumo MD Department of Urology, Tokyo Electric Power Hospital, Shinanomachi 9-2, Shinjuku-ku, Tokyo 160-0016, Japan. Email: t0621888@pmail.tepco.co.jp

Abstract

AbstractBackground: The effects of age and concomitant chronic illness on male sexual function were investigated to obtain insight into the prevention of erectile dysfunction (ED).

Methods: A questionnaire from the International Index of Erectile Function (IIEF) was given to 2311 non-institutionalized men aged 23–79 years along with a survey of health status. The study sample consisted of 1517 men who provided complete responses to the questionnaire. For statistical analysis, ANOVA was conducted to evaluate the effect of aging on the sexual functions and a logistic regression model was used to identify significant independent risk factors for ED.

Results: There was a significant correlation between age and the scores for erectile function, orgasmic function, sexual desire and intercourse satisfaction. The prevalence of moderate and severe cases of ED were 1.8% and 0% for ages 23–29; 2.6% and 0% for ages 30–39; 7.6% and 1.0% for ages 40–49; 14.0% and 6.0% for ages 50–59; 25.9% and 15.9% for ages 60–69; and 27.9% and 36.4% for ages 70–79 years, respectively. Hypertension, diabetes mellitus, heart disease, chronic hepatitis, disc herniation and cerebral infarction under treatment with anticoagulants were significant independent risk factors for ED.

Conclusions: The results obtained indicated a significant association between aging and chronic diseases and erectile function. Further epidemiologic research and analysis of individual risk factors are required to allow more effective future strategies for the treatment and prevention of ED.

Introduction

Erectile dysfunction (ED) is defined by the National Institutes of Health (NIH) Consensus Development Conference as the inability to attain and/or maintain penile erection sufficient for satisfactory sexual performance.1 Erectile dysfunction is not a life-threatening disorder, but it influences the daily routine, social interactions, well-being and quality of life of the patient. The etiology of ED indicates that a number of factors contribute to the disorder. The effects of age and concomitant chronic illnesses such as diabetes, vascular disease, hepatic failure, chronic renal failure and neurologic disease are well documented. Also well documented is the role of some drug groups, certain types of surgery, injuries and although sometimes controversial, the role of risk factors related to lifestyle such as smoking, alcohol consumption and inappropriate dietary habits accompanied by an abnormal serum level of cholesterol. An understanding of the prevalence and characteristics of risk factors for ED is required for the establishment of therapeutic strategies to treat the disorder.

Recently, Rosen et al. developed an International Index of Erectile Function (IIEF), a multidimensional scale for assessment of erectile function and reported that it has excellent reliability, validity and sensitivity.2 Utilizing this scale as an index to evaluate the sexual function of males leading ordinary lives, the current study investigated the effects of aging and risk factors on male sexual function and estimated the prevalence of ED to obtain an insight into the prevention of the disorder.

Methods

Study sample

The study sample consisted of employees of 11 companies with head offices in Tokyo, Kyoto or Osaka, and fathers of employees of a company with a head office in Tokyo. Subject ages ranged from 23 to 71 years for the employees and 60 to 79 years for the fathers. The study was conducted from 1 December 1997 to 30 September 1999. Complete responses to the questionnaire were provided by 1051 of the 1104 employees (95.2%) and 466 of the 1207 fathers (38.6%). Occupations the respondents were engaged or had been engaged in were: salesperson (n = 611), office clerk (401), general manager (202), manufacturing (134), specialist or engineer (94), transportation (24), construction (17), agriculture and forestry (17), and other work (17). These 1517 respondents constituted the present study sample. Of these subjects, 119 were in their 20s, 384 in their 30s, 306 in their 40s, 238 in their 50s, 311 in their 60s and 159 in their 70s. The number of men unmarried or not living with a spouse was 65 for ages 23–29 years (54.6%), 38 for ages 30– 39 years (9.9%), four for ages 40–49 years (1.4%), three for ages 50–59 years (1.3%), two for ages 60–69 years (0.6%) and seven for ages 70–79 years (4.4%).

Questionnaire

The Japanese version of the IIEF, which has been verified in terms of validity, reliability and sensitivity,3 was used in this study. An optimal Japanese translation of the IIEF has been achieved by repeated translation from English to Japanese and back into English, preserving the content from the original English version. The questionnaire consists of 15 questions in five domains (see Appendix I), including six questions on erectile function (EF; questions 1–5 and 15), two questions on orgasmic function (OF; questions 9 and 10), two questions on sexual desire (SD; questions 11 and 12), three questions on intercourse satisfaction (IS; questions 6–8) and two questions on overall satisfaction (OS; questions 13 and 14). The responses to each question were rated on a six-grade scale (0–5) or a five-grade scale (1–5). The scores for each domain were totaled and analyzed.

Data collection

Each candidate for this survey was informed in writ-ing of its purpose and our intention to keep the information concerning all individuals and organizations confidential. Each questionnaire was sealed in an envelope and returned by either dropping into a collection box set up at the participating organization or by mail directly to our department. When answering the questions on sexual function, the respondent was also requested to give the following information: age, name of diseases that he had been diagnosed with or was receiving treatment for, diseases which he experienced in the past, marital status, occupation, and the date the questionnaire was filled out.

Data analysis

Prevalence of diseases was analyzed in all of the 1517 respondents. The effect of aging on sexual function was analyzed in 1398 men who live with their spouses. The prevalence of men who have intercourse less than once a month or men suffering from ED were determined from the scores of questions 6 and 15, respectively. The degree of ED was estimated from the score in question 15 and men who responded ‘Low’ were classified as having moderate ED and men who responded ‘Very low’ were classified as having severe ED. The significance of risk factors for ED, as the effects of diseases on erectile function, was analyzed in 1014 men aged 40–79 years.

Statistical analysis

For statistical analysis, ANOVA was conducted for evaluation of the effect of aging on sexual functions and provided there was a significant difference, Scheffé's post-hoc procedure was applied to the data. In an attempt to identify a significant set of risk factors for ED among the diseases, a logistic regression model was used. The end-point was defined as having moderate or severe ED as described. Each disease was first assessed by univariate logistic regression analysis. Significant factors were then subjected to multivariate logistic regression analysis to identify the independent risk factors for ED. All values for IIEF score are expressed as the mean ± SD and statistical significance was set at P < 0.05. All analyses were completed using Stat View 5.0 for Macintosh (SAS Institute, Cary, NC, USA).

Results

Aging and sexual function

When the effects of aging were correlated with IIEF scores in each domain, advanced aging coincided with significantly lower scores for EF, SD, IS and OS (Table 1). Average scores for EF, SD and IS for the elderly (ages 60–79 years) were from approximately 50% to 30% of those for younger men aged 23–39 years. In contrast, the OS score decreased, but not as markedly as the scores for other domains.

Table 1.  International Index of Erectile Function scores for men in different age groups
  International Index of Erectile Function score
Age
(years)
No.
subjects
Erectile functionOrgasmic functionSexual desireIntercourse satisfactionOverall satisfaction
  1. Values within each score category that have different letters are statistically different (P < 0.05).

23–295427.0 ± 5.1a9.3 ± 1.7e7.9 ± 1.5i10.3 ± 4.2m7.2 ± 1.9r
30–3934625.4 ± 6.7a8.9 ± 2.4e7.4 ± 1.7i8.8 ± 4.2mn6.8 ± 1.6r
40–4930223.2 ± 9.0ab8.1 ± 3.2ef6.8 ± 2.1j7.9 ± 4.4no6.7 ± 1.5r
50–5923520.6 ± 9.7b7.1 ± 3.6f6.2 ± 2.2j7.0 ± 4.5o6.6 ± 1.4r
60–6930914.4 ± 10.6c4.8 ± 4.0g5.3 ± 2.6k4.8 ± 4.6p6.1 ± 1.5s
70–791528.6 ± 9.2d2.9 ± 3.8h3.7 ± 2.7l2.4 ± 3.9q5.7 ± 1.7s

Age-related prevalence of erectile dysfunction

The prevalence of men who have intercourse less than once a month was 11.1–15.3% in the younger age groups (23–39 years), 22.2–25.1% in the middle age groups (40–59 years) and 44.7–68.8% in the older age groups (60–79 years). The number of men with ED increased with advancing age (Fig. 1). The prevalence of moderate and severe ED was 1.8% and 0% for ages 23–29, 2.6% and 0% for ages 30–39, 7.6% and 1.0% for ages 40–49, 14.0% and 6.0% for ages 50–59, 25.9% and 15.9% for ages 60–69, 27.9% and 36.4% for ages 70–79, respectively.

Figure 1.

The prevalence of erectile dysfunction (▪) and of men who have intercourse less than once a month (□). Values for the prevalence of men with erectile dysfunction represent the incidence of subjects who responded ‘Low’ or ‘Very low’ to question 15 of the International Index of Erectile Function questionnaire.

Diseases and sexual function

Major current diseases or diseases for which the subjects were receiving treatment included hypertension, hyperlipidemia, gastroduodenal ulcers, diabetes mellitus, hyperuricemia, allergic diseases, heart disease, hepatic diseases, disk herniation and cerebral infarction in the older age group (Table 2). In addition, there were dermatologic diseases such as eczema in five subjects, chronic nephropathies in five subjects, benign or malignant colorectal diseases in five subjects, chronic obstructive pneumopathies in four subjects and other conditions in 32 subjects.

Table 2.  Prevalence of relatively common diseases in respondents to the International Index of Erectile Function questionnaire
DiseasePrevalence (%)
 23–29 years30–39 years40–49 years50–59 years60–69 years70–79 years
 (n = 119)(n = 384)(n = 306)(n = 238)(n = 311)(n = 159)
  1. Subjects include all the respondents with or without spouses.

Hypertension01.07.817.232.237.7
Hyperlipidemia0.82.12.94.64.56.3
Peptic ulcer0.80.82.03.87.13.8
Diabetes00.31.62.96.87.5
Hyperuricemia01.33.33.47.44.4
Allergic diseases1.73.61.62.51.95.0
Cardiac diseases00.30.32.19.616.4
Hepatic diseases1.70.31.00.43.95.0
Disk herniation00.51.61.73.21.3
Cerebral infarction000.301.95.7

The effects of selected diseases upon the erectile function in subjects aged 40–79 years were determined. Hyperlipidemia, peptic ulcer, hyperuricemia and allergic diseases were not significant risk factors as determined by univariate logistic regression analysis (Table 3). In contrast, hypertension, diabetes mellitus, heart disease, chronic hepatitis, disc herniation and cerebral infarction receiving anticoagulants were significant independent risk factors for ED as determined by multivariate logistic regression analysis (Table 4). Because the prevalence of other diseases was very low, the statistical significance of their effects was not tested. However, the scores for erectile function were particularly low in at least half of the subjects with colorectal cancer who were receiving anticancer chemotherapy and those with chronic obstructive pneumopathies.

Table 3.  Significance of risk factors for erectile dysfunction in 1014 men aged 40–79 years according to univariate logistic regression analysis
DiseaseNo. sufferers
(yes/no)
No. men with ED
(yes/no)
P-valueOdds
ratio
95% confidence
interval
  1. The end-point was defined as having moderate or severe erectile dysfunction (ED), where the degree of ED was estimated from the score in question 15 of the International Index of Erectile Function questionnaire; men who responded ‘Low’ were classified as having moderate ED and men who responded ‘Very low’ were classified as having severe ED.

Hypertension223/791108/199< 0.00012.79372.053–3.801
Hyperlipidemia45/96917/2900.26251.42150.766–2.638
Peptic ulcer46/96817/2900.31281.37050.741–2.533
Diabetes46/96828/279< 0.00013.84142.091–7.058
Hyperuricemia45/96916/2910.43041.28540.688–2.403
Allergic diseases16/9986/3010.52611.38930.500–3.858
Cardiac diseases62/95240/267< 0.00014.66462.721–7.998
Hepatic diseases23/99114/2930.00123.70571.586–8.657
Disk herniation9/10058/2990.000118.88962.352–151.724
Cerebral infarction15/99914/293< 0.000133.73374.415–257.758
Table 4.  Final multivariate logistic regression analysis for significance of independent risk factors for erectile dysfunction in 1014 men aged 40–79 years
VariableEstimate ±
standard
error
P-value95%
confidence
interval
  1. Analysis was conducted for diseases which were shown to be significant by univariate logistic regression analysis. The end-point was defined as having moderate or severe erectile dysfunction.

Hypertension0.750 ± 0.170< 0.00011.518–2.954
Diabetes0.982 ± 0.336< 0.00341.383–5.154
Cardiac
diseases
1.170 ± 0.292< 0.00011.817–5.716
Hepatic
diseases
1.075 ± 0.4590.01921.192–7.203
Disk herniation2.636 ± 1.0920.01581.640–118.750
Cerebral
infarction
3.055 ± 1.0560.00382.679–168.120

Discussion

This study has documented the age-related prevalence of and risk factors for ED in 1517 non-institutionalized men aged 23–79 years, using a self-administered measure of erectile function, the IIEF questionnaire.

The first study to demonstrate reliable data on the prevalence of ED in a large population sample was conducted by Kinsey et al. in 1948.4 This study evaluated 15 781 men in the general population who were classified by age, education, occupation and residence. Erectile dysfunction was found to be an age-dependent disorder with a prevalence ranging from 0.1% at 20 years of age to 75% at 80 years. Long after Kinsey's study, the Massachusetts Male Aging Study (MMAS) reported the prevalence of ED in a general population of 1290 men from 40 to 70 years of age, using adequate epidemiologic methods to measure the prevalence of the condition.5 Baseline data from the MMAS study suggested that the combined prevalence of minimal, moderate and complete ED was as high as 52%. The prevalence of minimal ED was 17%, while that of moderate and complete ED was 25% and 10%, respectively.5 The prevalence increased with age from 38% in the youngest group of men to almost 70% in the oldest men examined. The frequency of minimal ED remained stable at around 17% throughout the age range, but the oldest men were three times more likely to have complete ED than the youngest men.5

Data on the prevalence of ED in 3940 Japanese married men aged 20–94 years who underwent health examinations or were members of senior social clubs was reported in 1995.6 According to this survey, about 2.5% of the population had complete or partial ED at age 20–44 years, 10% at 45–59 years, 20% at 60–69 years and 33% at 70–79 years. The prevalence of ED therefore increased markedly for men over 60 years of age.

Since Kinsey's original study, there have been numerous other epidemiologic surveys conducted in selected populations with different medical problems, in the elderly, or in small patient samples.7–10 Although undertaken in different settings and with populations of different ages, all of these studies have shown that ED is associated with aging.

As a cause of impairment of sexual functions in aged men, there is a well-documented age-related decrease in serum androgen levels,11,12 but it has not been convincingly demonstrated that a decreased serum testosterone concentration contributes to ED. A study in healthy aged men showed that free and albumin-bound testosterone rather than total testosterone concentrations were correlated positively with sexual desire and sleep-related erection, but not with erectile dysfunction or frequency of intercourse.13 As changes in the structure of the tunica albuginea of the penis have also been implicated as a possible cause of ED in healthy elderly men, another study investigated whether such changes influence the development of ED.14 It was concluded that decreased elastic fiber concentration and changes in microscopic features of the tunica albuginea may contribute to erectile dysfunction by impairing the veno-occlusive function of the penis.

In general, there is no doubt that ED is associated with age, but there are a wide range of medical problems and their associated treatments that could possibly impair erectile function and these are increasingly common with advancing age. In the present study, cardiovascular diseases, diabetes mellitus, hepatic diseases, disk herniation and cerebral infarction were shown to have a significant association with erectile function. Cardiovascular diseases are a well-documented cause of arteriogenic ED, mainly via interference with the arterial inflow to the cavernous body. Erectile dysfunction may be associated with atherosclerotic vascular disease, peripheral vascular disease, hypertension, or myocardial infarction. In the MMAS study, the age-adjusted probability for complete ED was 39% in men with treated heart disease, as compared to 15% in untreated hypertensive patients and 9.6% in the total sample.5 Diabetes mellitus is one of the main systemic diseases causing ED. The mechanism by which diabetes causes ED is considered to involve multiple systems such as the autonomic nervous system, peripheral blood vessels and occasional psychologic factors. In the MMAS population, the age-adjusted probability of complete ED was three times greater for patients with treated diabetes than among controls without diabetes. The prevalence of ED in the diabetic men varied from 27.5% to 59%, depending on age.5 In the present study, hyperlipidemia did not significantly affect erectile function. The role of high serum cholesterol concentrations as a risk factor for sexual disorders in men is controversial,15 but in the MMAS study, HDL-cholesterol and serum dehydroepitestosterone levels were found to be inversely correlated with the probability of ED.5

The present results showed a discrepancy in that there was a minimal difference in the score for overall satisfaction according to age, despite the fact that erectile function as revealed by the questionnaire apparently differed among the age-stratified groups. Although the reason is unclear, decreased sexual desire with advancing age may minimize the sense of dissatisfaction with the sex life, related to question 13, or the sexual relationship with the partner, related to question 14 in the IIEF questionnaire. In addition, the lesser sexual activity of Japanese men, as compared with men in Western countries,16 may partly contribute to this result.

The present study was not a cross-sectional, random sample observational survey and therefore it may underestimate the prevalence of men with ED, since the unemployed, who receive less than ideal health-care, have been excluded from the sample. Such a population in Japan, however, represented less than 4.3% of the total population from 1997 to 1999 according to data from the Management and Coordination Agency. In contrast, the Ministry of Labor survey data from 1982 to 1992 on the prevalence of chronic diseases for each age group of workers was approximately equal to the prevalence of these diseases among the subjects of the current study.17

Although the present study produced fundamental data concerning the epidemiology of ED, the true incidence of ED in different countries and its prevalence due to individual risk factors are still difficult to ascertain. As the prevalence of ED depends upon the definitions used, the use of internationally established scales for the assessment of male sexual functions may facilitate comparisons of data from different countries. There is also a need for well-controlled studies that are large enough to document even a small incidence of disease or drug-related ED. Further epidemiologic research and analysis of individual risk factors is required. Such studies may clarify the interactive effects of organic factors and their probable etiology with patients' general physical, sociocultural and psychologic status. These efforts will hopefully lead to a reduction in unnecessary ED where substitution of treatment modalities for specific diseases is possible. Only then will it be possible to design more effective future strategies for the treatment and prevention of erectile dysfunction.

Appendices

Appendix I

The International Index of Erectile Function questionnaire2

All questions are preceded by the phrase ‘Over the past 4 weeks …’.

  • Q1. How often were you able to get an erection during sexual activity?
  • Q2. When you had erections with sexual stimulation, how often were your erections hard enough for penetration?0 = No sexual activity1 = Almost never/never2 = A few times (much less than half the time)3 = Sometimes (about half the time)4 = Most times (much more than half the time)5 = Almost always/always
  • Q3. When you attempted sexual intercourse, how often were you able to penetrate your partner?
  • Q4. During sexual intercourse, how often were you able to maintain your erection after you had penetrated your partner?0 = Did not attempt intercourse1 = Almost never/never2 = A few times (much less than half the time)3 = Sometimes (about half the time)4 = Most times (much more than half the time)5 = Almost always/always
  • Q5. During sexual intercourse, how difficult was it to maintain your erection to completion of intercourse?0 = Did not attempt intercourse1 = Extremely difficult2 = Very difficult3 = Difficult4 = Slightly difficult5 = Not difficult
  • Q6. How many times have you attempted sexual intercourse?0 = No attempts1 = One to two attempts2 = Three to four attempts3 = Five to six attempts4 = Seven to ten attempts5 = Eleven or more attempts
  • Q7. When you attempted sexual intercourse, how often was it satisfactory for you?0 = Did not attempt intercourse1 = Almost never/never2 = A few times (much less than half the time)3 = Sometimes (about half the time)4 = Most times (much more than half the time)5 = Almost always/always
  • Q8. How much have you enjoyed sexual intercourse?0 = No intercourse1 = No enjoyment2 = Not very enjoyable3 = Fairly enjoyable4 = Highly enjoyable5 = Very highly enjoyable
  • Q9. When you had sexual stimulation or intercourse, how often did you ejaculate?
  • Q10. When you had sexual stimulation or intercourse, how often did you have the feeling of orgasm or climax?0 = No sexual stimulation/intercourse1 = Almost never/never2 = A few times (much less than half the time)3 = Sometimes (about half the time)4 = Most times (much more than half the time)5 = Almost always/always
  • Q11. How often have you felt sexual desire?1 = Almost never/never2 = A few times (much less than half the time)3 = Sometimes (about half the time)4 = Most times (much more than half the time)5 = Almost always/always
  • Q12. How would you rate your levels of sexual desire?1 = Very low/none at all2 = Low3 = Moderate4 = High5 = Very high
  • Q13. How satisfied have you been with your overall sex life?
  • Q14. How satisfied have you been with your sexual relationship with your partner?1 = Very dissatisfied2 = Moderately dissatisfied3 = About equally satisfied and dissatisfied4 = Moderately satisfied5 = Very satisfied
  • Q15. How do you rate your confidence that you could get and keep an erection?1 = Very low2 = Low3 = Moderate4 = High5 = Very high

Ancillary