BICYCLE RIDING AND ITS RELATIONSHIP TO THE DEVELOPMENT OF ERECTILE DYSFUNCTION

0022-5347/04/1723-1028/0 THE JOURNAL OF UROLOGY® Copyright © 2004 by AMERICAN UROLOGICAL ASSOCIATION

Vol. 172, 1028 –1031, September 2004 Printed in U.S.A.

DOI: 10.1097/01.ju.0000136461.84851.4a

Sexual Function/Infertility BICYCLE RIDING AND ITS RELATIONSHIP TO THE DEVELOPMENT OF ERECTILE DYSFUNCTION JOHN A. TAYLOR, III,* TZU-CHEG KAO, PETER C. ALBERTSEN

AND

RIDWAN SHABSIGH

From the Division of Urology, University of Connecticut Health Center, Farmington, Connecticut (JAT, PCA), Department of Biostatistics and Epidemiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland (T-CK), and Department of Urology, Columbia University, New York, New York (RS)

ABSTRACT

Purpose: Researchers have suggested that cycling is a hazard to the sexual health of men. Insufficient data have left cyclists skeptical of this claim. We explore risk factors within cycling that may put riders at risk for the development of erectile dysfunction (ED). Materials and Methods: We performed an Internet based survey of cyclists to examine factors associated with cycling that might contribute to ED as defined by the International Index of Erectile Function. A total of 688 cyclists were included in the analysis ranging in age from 18 to 77 years. Results: ED prevalence was 17% (115 of 688). Although results from univariate analysis revealed a correlation between ED and several tested variables, none proved to be statistically significant after controlling for age. Conclusions: The overall prevalence of ED in the cycling community does not appear to be greater than that of historical controls. Previously suggested alterations in riding habits may not change the prevalence of ED among cyclists. KEY WORDS: impotence, bicycling, data collection, internet

Researchers’ claims that cycling is a hazard to the sexual health of men have created much controversy.1 Prolonged pudendal pressure is the postulated mechanism of injury. Many within the cycling community are skeptical. Bicycle riding is used worldwide for transportation, sport and health related benefits. The suggestion that regular cycling can result in erectile dysfunction (ED)2 has broad social and financial impacts. There are 54,575,000 recreational cyclists in the United States alone.3 Of these cyclists 53% are men. Demographic data from the governing body for competitive bicycling in the United States reveal that 63% of the 56,228 members reported riding their bicycle more than 200 days per year.4 Group expenditures for cycling during a 1-year period were more than $122,570,040. With the success of American cyclists in events such as the Tour de France the awareness of cycling as a sport is increasing in the United States. In this study we identify risk factors specific to cycling that might correlate with the development of ED. MATERIALS AND METHODS

An institutional review board approved questionnaire developed at Columbia University was made available on the Internet at www.cyclingsurvey.com. Bicycling clubs and organizations within the United States were contacted and asked to notify members. In addition, several large bicycling groups added a direct link from their home pages to our study. Cyclists responding to the survey entered their name, e-mail address and birth date. Participation was verified by

confirming the e-mail account and associated name. Survey responses were stored separately from unique respondent identifiers. The questionnaire was divided into 3 main areas, comprised of an assessment of ED using the International Index of Erectile Function (IIEF),5 medical history and variables associated with bicycling. ED was defined as a score of 25 or less in the erectile function domain of the IIEF, which ensured identification of the mildest forms of ED. Questionnaires were submitted by 884 cyclists. Surveys were excluded if data were missing on age (79) or any portion of the IIEF (94), or the onset of ED occurred before cycling (23). The remaining 688 surveys were included in this analysis. Survey data were exported to an Excel (Microsoft Corporation, Redmond, Washington) file and read by SAS software (SAS Institute, Cary, North Carolina). A univariate analysis was performed first to identify those variables that correlated with the presence of ED. The chi-square or Fisher’s exact tests were used to test for these associations where appropriate with a significance level set at 5%. To test for differences between groups defined by ED-Yes and ED-No a 2-sample t test was used. Multivariate analysis was then performed using logistic regression analyses. Selection of variables was run by forward logistic regression including variables that met statistical significance on univariate analysis, as well as age group and all the domains of the IIEF (except overall satisfaction) at an entry significance level of 15%. Repeat univariate and multivariate analyses were then performed in identical fashion on age stratified subgroups.

Accepted for publication March 12, 2004. * Correspondence: Division of Urology, University of Connecticut RESULTS Health Center, 263 Farmington Ave., MC3955, Farmington, ConA total of 688 cyclists ranging in age from 18 to 77 years necticut 06030-3955 (telephone: 860-679-4299; FAX: 860-679-1276; completed the questionnaire and were included in the anale-mail: [email protected]). 1028

BICYCLE RIDING AND DEVELOPMENT OF ERECTILE DYSFUNCTION

ysis (table 1). ED was identified in 115 of 688 (17%) of cyclists. Mean age ⫾ SD of those with and without ED was 38.9 ⫾ 1.3 and 40.1 ⫾ 0.4 years, respectively and erectile function section scores were 13.6 ⫾ 0.6 and 29.6 ⫾ 0.1, respectively. Age stratification revealed ED prevalence rates of 27%, 12%, 11% and 21% in the 18 to 29, 30 to 39, 40 to 49, and 50 and older than 50 age groups, respectively. Comorbidities known to be associated with ED had the prevalence rates of hypertension at 7%, diabetes 2%, coronary artery disease 2% and tobacco use 3%. Univariate analysis (table 2) revealed that ED was positively associated (p ⬍0.05) with the presence of genital parasthesias after riding and the duration of parasthesias, and negatively associated with the number of years of cycling. ED was not associated with the number of miles ridden per week, classification, type of padding in or use of cycling shorts, use of aero bars, angle of the saddle, formula use for determination of saddle height, use of a professional to fit the bicycle, road vs mountain bicycle frame and primary material used in the frame. A subsequent multivariate analysis revealed that after controlling for age, none of the variables associated with cycling were statistically correlated with ED. Repeat evaluation of age stratified subgroups failed to reveal any significant association between ED and risk factors. DISCUSSION

The July 1997 issue of Bicycling Magazine reported an association between bicycle riding and the development of ED.1 This subject later became the topic of many news shows including a prime-time episode of the ABC News program 20/20 in July 1998.6 Researchers and cyclists assumed that increased mileage or time on a bicycle seat as well as the seat position were significant risk factors for ED. Recommendations to stand frequently during long rides to stay out of the “aero” position and to keep the nose of the seat tilted down rather than level or up were circulated. One study aimed to show that even recreational cyclists were at risk.7 Investigations sponsored by cycling companies were launched in an attempt to show saddle superiority with regard to pudendal pressure.8 Additional reports implicated bicycling “as a preventable source of morbidity” in the development of female sexual and urinary tract dysfunction, extrapolating pudendal neurovascular compression found in male subjects to female cyclists.9 Bicycle riding is used throughout the world for well-known exercise, fitness and recreational benefits. As such it is not surprising that these statements created much controversy. Research studies investigating the idea of perineal compression and its relationship to the development of ED have shown a decrease in pudendal artery flow and/or the partial pressure of oxygen (pO2) at the glans during riding. Nayal et

TABLE 1. Study population as defined by age, self-described level of cycling, and prevalence rates of ED and comorbidities No. subjects Mean age ⫾ SD No. age group: 18–29 30–39 40–49 50⫹ % ED Mean age without ED ⫾ SD Mean age with ED ⫾ SD % Cyclist ranking: Recreational rider Competitive racer Professional % Diabetes % Hypertension % Coronary artery disease % Tobacco use

688 40 ⫾ 10 137 222 194 135 17 40 ⫾ 0.4 39 ⫾ 1.3 37 58 5 2 7 2 3

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al demonstrated that transcutaneously measured pO2 at the glans decreases from 61.4 mm Hg while standing to 19.4 mm Hg after 3 minutes in the seated position and returns to normal levels with standing.10 A later study by Sommer et al that documented a 61% prevalence of genital numbness attempted to correlate this finding with a decrease in glandular pO2.11 Although ED was noted in 19% of cyclists who logged more than 400 kilometers per week, the correlation between genital numbness, decreased glandular pO2 and ED was not tested. Furthermore the main issue of whether or not cyclists were at increased risk for the development of ED was not addressed. The prevalence of ED within the general population has been previously reported. The Massachusetts Male Aging Study found the prevalence of ED to be 52% in men between the ages of 40 and 70 years (mean 53.8 ⫾ 8.5),12 and the National Health and Social Life Survey noted a prevalence of 11% in men between the ages of 18 and 59.13 Lockhart et al recently reported prevalence rates in the international community, and found rates of 3% to 8% in the 20 to 29-year-old age range, and rates of 9%, 21% and 40% to 75% for those in the 30 to 39, 40 to 49 and 50 years old or older age groups, respectively.14 One study looked at the prevalence of ED within a group of cyclists compared to swimmers, and found rates of 4% and 2%, respectively.15 Although there was a 10-year age difference between the groups, the authors concluded that cyclists have a 50% higher risk of ED. This study also reported the prevalence of parasthesias but failed to correlate the presence with that of ED. Our study investigated the prevalence of ED and the potential risk factors associated with cycling (table 2). A well established tool, the IIEF, was used to define ED. Compared to historical controls, we did not find higher prevalence rates of ED for cyclists as a whole. Age groupings that correspond to the Massachusetts Male Aging Study and National Health and Social Life Survey yielded a prevalence rate of 16% and 16.7%, respectively. Analysis of risk factors for the group as a whole revealed few positive correlations with the development of ED. The presence and duration of parasthesias after riding, presumed due to perineal nerve compression, were found to be associated with the presence of ED. However, the majority of risk factors related to neurovascular compression were not found to have a strong relationship with the development of ED. The length of exposure to perineal pressure as defined by the number of miles per week and cycling category were not correlated with ED. How cyclists described their bicycle riding, professional versus recreational, did not correlate with the presence of ED. Interestingly, cyclists with a long history of riding had a lower rate of ED compared to riders with a short history of cycling. This finding held true for all the age group subcategorizations. Variables related to the intensity of perineal compression also failed to demonstrate a relationship to ED. Included among these variables were the up or down angle of the seat, the use of aero bars for a more forward position resulting in increased pressure on the bulbar region, and the degree or type of bike short/seat padding. Multivariate analysis revealed that the only significant risk factor in our group was age. Whether the high prevalence of ED seen in the youngest riders is representative of the community or simply a result of response bias cannot be determined from our data, but it would seem that pudendal pressure is not a factor. Extrapolation from perineal compression of neurovascular structures to parasthesias and, therefore, potentially to ED, was not supported by our analysis. The limitations of our study stem from the study design. Certainly there is a potential for response bias, but had this been a major factor we would have expected a higher overall prevalence rate of ED because impotent cyclists would probably have had a stronger incentive to respond to an Internet

1030

BICYCLE RIDING AND DEVELOPMENT OF ERECTILE DYSFUNCTION TABLE 2. Association of risk factors with the presence of ED by univariate analysis No. ED-Yes (%)

No. ED-No (%)

Total

p Value

Comorbidities Hypertension: Yes No Heart attack: Yes No Diabetes: Yes No Tobacco: Yes No Alcohol: Yes No Prior ED treatment: Yes No Age: 18–29 30–39 40–49 Older than 50

10 105

(21) (16)

37 (79) 556 (84)

47 641

0.3852

2 113

(17) (17)

10 (83) 561 (83)

12 674

0.9827

2 113

(14) (17)

12 (86) 559 (83)

14 672

0.8020

3 111

(13) (17)

20 (87) 551 (83)

23 662

0.7824

84 31

(17) (17)

422 (83) 150 (83)

506 181

0.8707

10 104

(56) (16)

8 (44) 564 (84)

18 668

0.0001*

36 26 24 29

(26) (12) (12) (21)

101 (78) 197 (88) 169 (88) 106 (79)

137 223 193 135

0.0005*

67 48

(21) (13)

251 (79) 319 (87)

318 367

0.0053*

102 13

(17) (18)

512 (83) 60 (82)

614 73

0.7958

42 65 8

(17) (16) (23)

210 (83) 336 (84) 27 (77)

252 401 35

0.5997

56 58

(14) (20)

336 (86) 236 (80)

392 294

0.0581

78 36

(16) (19)

420 (84) 153 (81)

498 189

0.2869

13 93 9

(19) (17) (15)

54 (81) 459 (83) 52 (85)

67 552 61

0.7789

49 21 12 31

(15) (16) (21) (19)

278 (84) 109 (84) 46 (79) 134 (81)

327 130 58 165

0.5925

7 (17.5) 8 (17) 97 (17) 3 (9)

33 (82.5) 40 (83) 466 (83) 31 (91)

40 48 563 34

0.651

41 74

(16) (17)

220 (84) 364 (83)

261 425

0.5621

21 31

(15) (18)

119 (85) 146 (82)

140 177

0.5483

24 21 3 3

(21) (17) (8) (7)

92 (79) 100 (83) 35 (92) 39 (93)

116 121 38 42

0.1653

33 (15) 18 (20) pressure

194 (85) 71 (80)

227 89

0.2164

Duration of pudendal pressure Yrs cycling: 10 or Less Greater than 10 Miles wkly: Less than 200 200 or Greater Cycling category: Recreational Competitive racer Professional Intensity of pudendal pressure Stationary trainer (riding in place on bike stand or rollers): Yes No Aero bars (allows more forward position with greater pressure on bulbar region): No Yes Seat angle: Nose down Level Nose up Saddle composition (degree of padding): Leather Foam Gel Combination Cycling short composition (degree of padding): Do not wear Cotton Chamois Duel Formula for saddle ht (allows for optimal leg extension during revolution): Yes No Bike professionally fit (provides optimal positioning on bike): Yes No Frame composition (Variable characteristics for transmission of road vibration): Aluminum Steel Titanium Carbon-fiber Bike frame type: Road Mountain (off-road) Parasthesias associated with pudendal Presence of parasthesias: Never Half the time or less More than half the time Miles associated with parasthesias: Not applicable 0–25 26–50 51–75 76–100 Greater than 100 Hrs parasthesias: Not applicable Less than 1 1–5 5⫹ Cycling variables categorized by relationship with pudendal pressure. * Statistical significance (p ⬍0.05).

19 84 12

(15) (16) (33)

112 (86) 437 (84) 24 (67)

131 521 36

0.0209*

33 19 25 16 9 12

(15) (19) (16) (18) (13) (30)

186 (85) 83 (81) 136 (84) 72 (82) 62 (87) 28 (70)

219 102 161 88 71 40

0.2691

160 (84) 338 (84.5) 52 (83) 19 (61)

190 400 63 31

0.0103*

30 (16) 62 (15.5) 11 (17) 12 (39)

BICYCLE RIDING AND DEVELOPMENT OF ERECTILE DYSFUNCTION

survey. In fact, this may be the explanation for the high rate seen in the young subgroup. Another potential issue concerns response rate. A response rate of 688 may have had insufficient power to detect subtle relationships between cycling risk factors and ED. However, it is unlikely that we failed to detect a major correlation. Based on our analysis we have been unable to show any significant relationship between bicycle riding and ED. Large case-control studies are needed to confirm or refute this hypothesis. CONCLUSIONS

ED exists within the cycling community with an overall prevalence rate that is lower than historical studies. Based on an Internet survey of 688 cyclists, we have been unable to demonstrate a statistically significant correlation between variables associated with pudendal pressure and the presence of ED. Larger case-control studies are needed to define the relationship between bicycle riding and ED if it exists. REFERENCES

1. Kita, J.: The unseen danger. Bicycling, pp. 69-73, 1997 2. Goldstein, I. J. in Kita, J.: The unseen danger. Bicycling, pp. 69-73, 1997 3. 1999 Superstudy of Sports Participation, America Sports Data, Inc. 4. USA Cycling Demographics, USA Cycling 5. Rosen, R. C., Riley, A., Wagner, G., Osterloh, I. H., Kirkpatrick, J. and Mishra, A.: The International Index of Erectile Function (IIEF): a multidimensional scale for assessment of erectile dysfunction. Urology, 49: 822, 1997

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6. Goldstein, I. J. in Johnson, T.: The perils of pedaling: bike riders’ lament. ABCNews.com (20/20), July 21, 1998 7. LaSalle, M. D., Wen, C., Choi, M., Salimpour, P., Adelstein, M., Gholami, S. et al: “You don’t have to ride the Tour de France”: erectile dysfunction in 81 consecutive riders. J Urol, suppl., 161: 269, abstract 1041, 1999 8. Mingrino, A.: Evaluation of different saddles and analysis of the problems arising from them. Atti Ist Ven LL SS AA, 156: 197, 1998 9. LaSalle, M., Salimpour, P., Adelstein, M., Mourtzinos, A., Wen, C., Renzulli, J. et al: Sexual & urinary tract dysfunction in female bicyclists. J Urol, suppl., 161: 269, abstract 1040, 1999 10. Nayal, W., Schwarzer, U., Klotz, T., Heidenreich, A. and Engelmann, U.: Transcutaneous penile oxygen pressure during bicycling. BJU Int, 83: 623, 1999 11. Sommer, F., Konig, D., Graft, C., Schwarzer, U., Bertram, C., Klotz, T. et al: Impotence and genital numbness in cyclists. Int J Sports Med, 22: 410, 2001 12. Feldman, H. A., Goldstein, I., Hatzichristou, D. G., Krane, R. J. and McKinlay, J. B.: Impotence and its medical and psychosocial correlates: results of the Massachusetts Male Aging Study. J Urol, 151: 54, 1994 13. Laumann, E. O., Gagnon, J. H., Michael, R. T. and Michaels, S.: The Social Organization of Sexuality: Sexual Practices in the United States. Chicago: The University of Chicago Press, 1994 14. Lockhart, D., Shabsigh, R. and Perelmen: Prevalence of ED using a common methodology in six Countries. Int J Imp Rsch, suppl., 14: S25, 2002 15. Schwarzer, U., Wiegand, W., Bin-Saleh, A., Lo¨tzerich, H., Kahrmann, G., Klotz, T. et al: Genital numbness and impotence rate in long distance cyclists. J Urol, suppl., 161: 178, abstract 686, 1999