Original Research

International Journal of Impotence Research (2004) 16, 358–364. doi:10.1038/sj.ijir.3901155 Published online 12 February 2004

Erectile dysfunction in primary care: prevalence and patient characteristics. The ENIGMA study

B J de Boer1, M L Bots1, A A B Lycklama a Nijeholt2, J P C Moors3, H M Pieters1 and Th J M Verheij1

  1. 1Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands
  2. 2Department of Urology, Leiden University Medical Center, Leiden, The Netherlands
  3. 3General Practitioner, Rosmalen, The Netherlands

Correspondence: BJ de Boer, MD, Julius Center for Health Sciences and Primary Care, Department of General Practice, University Medical Center of Utrecht, PO Box 85060, 3508 CG Utrecht, The Netherlands. E-mail: l.j.deboer@med.uu.nl

Received 14 November 2002; Revised 30 July 2003; Accepted 31 July 2003; Published online 12 February 2004.



The availability of adequate treatment for erectile dysfunction (ED) triggers studies into the prevalence of ED in the general population. Yet, previous studies showed different prevalence estimates partly due to differences in patient selection, in (unclear) definitions of ED and in assessment. ENIGMA has been designed to study the prevalence of ED in the general population of The Netherlands, using the WHO definition with a description of the way of assessment. In all, 5721 mail surveys were sent to all men, aged 18 y and older in 12 general practices in The Netherlands. A total of 5601 were included in the study and 2117 (38%) were completed. A total of 38% of the men reported to have ever had some kind of erectile problem. The prevalence of ED was 17% (6% mild, 4% moderate and 7% complete). Age, diabetes, cardiovascular diseases, penile disorders, irradiation in the pelvic region, relational problems, fear for failure, surmenage, medication use and regular consumption of alcohol were independently related to ED. Men with ED were less content with their (sexual) life and had less confidence in sexual performance. Presence of ED was negatively related to affected happiness in life. ED is commonly found in men and is related to age, medication, comorbidity and lifestyle factors. Men with ED perceive a lower quality of (sex)life. Doctors should be aware of the presence of ED and its consequences in patients.



Erectile dysfunction (ED) appears to be common among men, and may have a considerable impact on the quality of life.1, 2, 3, 4 Since a proportion of these men seek medical attendance, data on the prevalence of ED are relevant for public health.5 Over the past years, many studies have been published on the prevalence of ED in the general population.5, 6, 7, 8, 9, 10, 11, 12, 13 The prevalence estimates differ considerably because of differences in the way of assessment, in the definitions of ED and in the risk of ED in the populations (population selection). In many studies, the definition of ED and the way of assessment were not clearly reported.8 ENIGMA is a study on the prevalence of ED in the general population of The Netherlands, using the most recent definition of WHO and presenting clearly the way of assessment.


Participants and methods

The study sample

To all men aged 18 y and older, registered in 11 general practices in Maarssenbroek (semi-urban area in the middle of The Netherlands), and all men aged 65 y and older, registered at the general practice 'Herenstraat' in Breukelen, a mail survey was sent on sexual problems and ED. Excluded were men who were incapable of completing a questionnaire, because they were too ill, had a mental incapacity or lack of knowledge of the Dutch language. Reminders were sent after 1 month and after 3 months. To explore whether the nonparticipating subjects differed from the participating subjects, a nonresponse study was executed by sending a short questionnaire to men aged 40–70 y (one question on ED) who had previously not responded to the first questionnaire and the reminders. The ENIGMA study was approved by the medical ethics committee of the University Medical Center Utrecht, Utrecht, The Netherlands.

Assessment of ED

ED was defined according to the WHO definition as follows: an ED is a continuous or repetitive inability to achieve or maintain an erection sufficient for a satisfying sexual activity.14, 15 Apart from ED, information was collected on medical history, quality of life, sexuality and lifestyle. The ENIGMA questionnaire comprised 29 questions on ED (see Appendix A).

If a participant answered positively on the questions 'ever had problems with the erection' or 'ever had problems with obtaining or maintaining an erection firm enough for sexual activity', he was defined as 'ever had erectile problems'.

The algorithm for ED according to the definition of WHO is given at the bottom of Appendix A. When the dysfunction occurred (almost) every time then ED was defined as complete, if it occurred most of the times or 50% of the times then ED was defined as moderate, and if it occurred seldom then ED was defined as minimal. The questionnaire comprised the International Index on Erectile Function (IIEF-5) and the Leidse Impotence Scale Test (LIST).16, 17 As a pilot study, the questionnaire was evaluated first in a small number of men in the general population for both its comprehensibility and its sensitivity.

Determinants of sexual dysfunction

Information on a variety of potential risk factors was obtained by a questionnaire. The age reflects the age in years at the moment the participant completed the questionnaire. Data on medical conditions possibly related to ED (such as artherosclerosis, angina pectoris, multiple sclerosis, myocardial infarction, hypertension, diabetes mellitus, cerebral vascular accident, neurological problems in the spine or elsewhere, penile disorders, pelvic surgery, accidents or irradiation) and psychological problems possibly related to ED (such as depression, relational problems, problems at work, insecurity, fear for failure, stress and surmenage) were obtained by questioning 'Do you have, have not, do not know, or unknown...' (in nonmedical terms). Information on current smoking, alcohol use and use of drugs was obtained by asking 'Do you..., how many a day/week, has it changed during last year?' Information on currently used medication, including dose and frequency, was also obtained. The medication was divided in three groups: (1) no allopathic medication (group 2), (2) allopathic medication not described in the literature as related to ED (group 1), and (3) allopathic medication that is known to be related to ED (group 0). If a participant reported the use of any kind of medication in the 'related to ED group of medication', he was categorised in group 0.

Information on other aspects of sexual life was obtained by asking 'Did you have sex at all in the last 6 months, if yes, what was the average frequency of sex in the last 6 months, are you content about your sexual life, do you regard yourself sufficiently interested in or in the mood for sex, do you have orgasmic problems, what confidence do you have in getting an erection during sexual intercourse or during masturbation?' Information on general health was obtained by asking 'How do you describe your general health, what is the score on happiness in general (range from 1 to 9), What is the level of contentment in life in general and what influence does the erectile dysfunction have on your level of happiness?'

Statistical analysis

Overall and age-specific prevalence estimates were calculated and presented with 95% confidence limits. Logistic regression analysis was applied to study the independent relations of potential determinants to ED. First, to determine which of the patient characteristics were related to ED, we performed univariate analyses. Second, all the determinants were studied in a multivariate model that comprised all the factors considered in the univariate analyses. Using the same approach, the relation of sexual factors and general health characteristics to ED was evaluated. Results were expressed as odds ratios (OR) with corresponding 95% confidence intervals. All analyses were performed using SPSS 10.0.



A questionnaire was sent to 5721 men. In all, 102 had moved out of the general practice and 18 were incapable of answering the questionnaire, yielding an eligible population of 5601 men for the study. The questionnaire was returned by 2452 men (44%). Completed questionnaires were obtained from 2117 men (38%). In Figure 1 the general characteristics of the ENIGMA study participants and the nonresponders are shown. The mean age of the 2117 participants was 46.5 y (range 18–91), which was not statistically significantly different from the mean age of the eligible population (45 y). Of all participating men, 87.4% were sexually active, 1.6% homosexual and 2.2% bisexual. A total of 89.1% had a permanent sexual partner. Of the participants, 812 (38.4%) reported to have ever had problems with getting or maintaining an erection. The prevalence of ED was 16.8% (356 men) (5.9% mild ED, 3.6% moderate ED and 6.9% complete ED) (Table 1).

Figure 1.
Figure 1 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

Design of the ENIGMA study.

Full figure and legend (50K)

In the nonresponse study among men aged 40–70 y, the overall response rate was 45% (226/500), of which 151 completed questionnaires were obtained (30%). The prevalence of ED in this group, based on answering one question only, was 9.9%.

Patient characteristics for ED

In Table 2 the relation of patient characteristics and ED is presented. Adjusted analyses showed a positive statistically significant relation between ED and age and several somatic patient characteristics (diabetes mellitus, hypertension, atherosclerosis, angina pectoris, previous myocardial infarction, previous stroke, spinal problems, problems of the central nervous system, penile disorders, previous lower abdominal surgery and history of pelvic irradiation). Of the more psychological related factors, significant relations were found for depression, relational problems, low self-esteem, fear for failure and surmenage. Of the lifestyle factors, significant relations were found for cigarette smoking, alcohol consumption and use of drugs, and use of allopathic medication.

Multivariate analyses showed that the relation with ED remained significant for increasing age, diabetes mellitus, penile disorders, pelvic irradiation, relational problems, fear for failure, surmenage, alcohol consumption and allopathic medication use. The goodness of fit of the multivariate model by the Hosmer of Lemeshow test was chi2= 6.30, P=0.61.

Table 3 presents the relation of other aspects of sexual life and general health factors with ED. All the characteristics were significantly related to ED in the age-adjusted analyses. In the multivariate analysis, independent factors related to ED were discontentment with life, discontentment with sexual intercourse, and less confidence in sexual performance (coitus and masturbation). The response whether ED would negatively affect the happiness of life was independently related to the presence of ED. The goodness of fit of the multivariate model by the Hosmer of Lemeshow test was chi2=6.00, P=0.65.



In the present study, 38.4% of the men aged 18 y or over reported to have ever had some kind of erectile function problem. The prevalence of ED (according to the WHO definition) was 16.8% of the population. Apart from age and allopathic medication, several somatic and psychological characteristics were related to ED. Of the lifestyle factors, only consumption of alcohol was independently related to ED. A low satisfaction and low confidence in the performance during sexual activity were independently related to ED. ED had a significant negative influence on the happiness of life.

A number of aspects need to be considered to appreciate the findings of ENIGMA. Firstly, the overall response rate in this study was 44%. Among those aged 40 y or over, a 50% response rate was found, which corresponds with those found in other studies.8, 9, 10, 11, 12, 13 A low response in young subjects may actually lead to an overestimation of ED prevalence in ENIGMA, whereas a low response rate in elderly may lead to an underestimation of the prevalence. In our nonresponse study, however, an ED estimate of 9.9% was found, clearly lower than in the overall population. This may indicate that our estimate might be a slight overestimation of the true ED in the population. Yet, one may wonder what kind of typical population the responding nonresponders is. Furthermore, comparison of our population with the Governmental Statistical Department data indicated that the ENIGMA population was similar to the general Dutch population with respect to age, health and diseases, ethnical background, smoking, alcohol and level of happiness, education level and state of marriage. Therefore, we feel that this large community-based study provides a good estimate of the prevalence of ED in the general male population in The Netherlands.

A comparison of our results with other studies performed in or close to The Netherlands (Boxmeer study, Krimpen study and Cologne study) showed more or less an agreement on the age-specific prevalence of ED across studies up to the age of 69 y.5, 6, 7 In the Boxmeer study, the prevalence of ED was somewhat lower (Figure 2). It should be taken into consideration that these studies all differed in the way of assessment of ED. In the Krimpen study, a single question was used emphasising the seriousness of the ED.6 In the Boxmeer study, both a single question and the sexual function inventory (SFI) were used. In the Cologne study, the Keed questionnaire (a validated questionnaire containing five questions on ED) was used.7 Therefore, a direct comparison of the findings across studies is hampered by the lack of information on how these questionnaires affect prevalence estimates of ED. The study by Dunn et al4 in the UK showed an overall prevalence of ED of 22%. The higher estimate compared to ENIGMA can mainly be explained by a higher mean age in the Dunn study (mean difference with ENIGMA of 3 y). Also, differences in assessment may contribute to observed differences across studies.

Figure 2.
Figure 2 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

Comparison between the age-related prevalence of ED in the ENIGMA study, the Krimpen study, the Boxmeer study and the Cologne study.

Full figure and legend (69K)

The observed relations of patient characteristics with ED are similar to those reported by others.8, 10, 13 Increasing age has been shown in most studies to be a risk factor.5, 6, 7, 8, 9, 10, 11, 12, 13 Previous cardiovascular events have repeatedly been reported as determinants of ED.18 In our study, only the combination of history of arteriosclerosis, angina pectoris, myocardial infarction and stroke showed an independent significant relation with ED, whereas the individual histories did not.

In contrast to other studies, hypertension was not independently related to ED.19 This might be a consequence of our statistical analyses in which we adjusted for a large number of other characteristics that may be related to hypertension. It is still a matter of debate whether hypertension per se or the medication for hypertension is considered responsible for ED.20 Our analysis in which medication use remained statistically significant related to ED independent of hypertension provides supportive evidence for the latter view.

Other conditions like diabetes mellitus,21, 22 (lower) abdominal surgery,23, 24 local irradiation25 and local penile disorders26 were also found as independent risk factors. In contrast with other studies, lower urine tract problems6 and smoking were not independently related to ED.27, 28 Many studies showed that smoking related to a 1.5- to 2.0-fold increased risk of ED. Also, pathophysiological studies provide evidence to suggest that the effect of smoking on the vascular system leads to an increased risk of ED. Our null finding may be explained by the fact that in ENIGMA, ex-smokers were included in the nonsmokers group, thereby potentially attenuating the relationship with ED.

The relation between depression and ED has been well documented.29 Yet in our analyses, depression as such was not significantly related to ED. This might be due to the extensive multivariate model in which a number of factors were included that may reflect part of the depression. Alternatively, in the analyses we adjusted for medication use, which, similar to the hypertension debate, may have attenuated the relation with depression.30

In conclusion, the ENIGMA study showed that ED is common among men and may have a considerable impact on the quality of life. GPs should be aware that this age-related condition is common among their patients especially among men at increasing age, or those with conditions like diabetes mellitus, penile disorders, pelvic irradiation, relational problems, fear for failure, surmenage, or those using alcohol regularly and those using allopathic medication. Additional studies are needed to indicate the effect of the risk factors in long-term follow-up and to evaluate the effect of intervention on ED and the quality of life in men with ED.



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Questions on erectile (dys)function*

  1. Have you ever noticed that your penis did not get rigid, while you wanted it to be (during sexual activity, for instance if you wanted to have intercourse)? Yes/No/I do not remember
  2. If yes is it still present at the moment? Yes/No
  3. How long ago did it start? 1–3 weeks/1–3 months/4–6 months/7–12 months/1–5 y/more than 5 y
  4. How long did it last? 1–3 weeks/1–3 months/4–6 months/7–12 months/1–5 y/more than 5 y
  5. How often did it happen or does it happen? (almost) every time, most of the times, as many times yes as no/seldom/(almost) never
  6. How much do you get bothered by it? Very much/much/moderate/little, not at all
  7. Were you less in the mood for sex in the last half year? Yes/No
  8. Are there any circumstances in which the penis does not get rigid? Yes/No
  9. Did you masturbate the last half year? Yes/No
  10. If yes, is the penis getting rigid enough (more than 50%) during masturbation? Yes/No
  11. If not, how often does the penis get insufficient rigid? (Almost) always/most of the times/as often yes as no/seldom/(almost) never
  12. Did the penis ever get not sufficient rigid during sexual activity? This means; there was sufficient stimulation and some form of rigidity, but not sufficient for a fulfilling sexual activity (for instance for sexual intercourse)? Yes/No/I do not remember
  13. Did the complaint start suddenly or more slowly? During weeks/during months
  14. If yes is it still present at the moment? Yes/No
  15. How long ago did it start? 1–3 weeks/1–3 months/4–6 months/7–12 months/1–5 y/more than 5 y
  16. How long did it last? 1–3 weeks/1–3 months/4–6 months/7–12 months/1–5 y/more than 5 y
  17. How often did it happen or does it happen? (almost) every time/most of the times/as many times yes as no/seldom/(almost) never
  18. How much do you get bothered by it? Very much/much/moderate/little/not at all
  19. Did the penis remain shorter rigid than you wanted? Yes/no/I do not remember
  20. How difficult was it to maintain your erection until the end of the sexual activity (for instance during sexual intercourse)? Did not try/very difficult/difficult/a little difficult/not very difficult/not at all difficult
  21. Is it still present at the moment? Yes/No
  22. How long ago did it start? 1–3 weeks/1–3 months/4–6 months/7–12 months/1–5 y/more than 5 y
  23. How long did it last? 1–3 weeks/1–3 months/4–6 months/7–12 months/1–5 y/more than 5 y
  24. How often did it happen or does it happen? (almost) every time, most of the times, as many times yes as no/seldom/(almost) never
  25. How much do you get bothered by it? Very much/much/moderate/little, not at all
  26. Do you notice any spontaneous erections, in the night or while waking up? Always/most of the times/sometimes/seldom/never
  27. How often during the last half year did you notice that? Never/once a month or less/more than once a month
  28. How rigid was the penis at most during last half year in the night or during waking up? 50% or less/more than 50%
  29. How strong is your confidence to obtain or maintain an election during sexual activity? Very strong/strong/more or less/weak/very weak or absent

*Originally in Dutch, translated into English.

ED (according to the definition of WHO)=(Q1: yes and Q2: yes and Q5: excluding seldom and (almost) never) or (Q12: yes and Q14: yes and Q11: excluding seldom and (almost never)) or (Q19: yes and Q21: yes and Q24: except for little and not at all) and (Q20: very difficult–little difficult).



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