The aim of the present study was to evaluate the relationship between motorcycling and erectile dysfunction (ED). We investigated the relationship between motorcycling and erectile function using the 5-items version of the International Index of Erectile Function (IIEF5) in 234 motorcyclists (response rate 75%) and 752 healthy controls (response rate 66%). In all, 161 (69%) of 234 motorcyclists were diagnosed as ED based on IIEF5. The prevalence of ED in the motorcycle group increased by age as: 58, 63, 76 and 93%, for motorcyclists in 20–29, 30–39, 40–49 and 50–59 years, respectively. There was a significant difference in the prevalence of ED between the motorcycle group and the control group in all age groups. On stepwise logistic regression analysis, motorcycling was the strongest risk factor for ED. Although the severity of ED in motorcyclists was not so severe, motorcycling may be one of risk factors for ED.
Several authors have suggested that bicycling may induce erectile dysfunction (ED) among some riders.1, 2, 3, 4 Perineal compression by the saddle during bicycling is thought to cause the ischemic neuropathy of penis and be responsible for ED.5 Motorcycling is similar to bicycling, to astride the saddle. Motorcycling differs from bicycling, in the engine with vibration and saddle design. The compression and vibration by the saddle during motorcycling may affect perineal neurovasculature and cause ED. Therefore, a question is raised regarding the relationship between motorcycling and ED. There is no report whether motorcycling may introduce ED or not, however. In the present study, we studied the prevalence of ED in members of an amateur motorcycle club in Japan, using the five-item version of the International Index of Erectile Function (IIEF5).
Annual meetings of amateur large-sized motorcycle members and their families took place at several districts in Japan (approximately, over 8 thousands). Of the 325 motorcyclists whom we gave a self-completion questionnaire concerning ED, 244 motorcyclists had responded (response rate 75%). These 325 motorcyclists joined this annual meeting and they belonged to some motorcyclist clubs at Kansai district in Japan. They had approximately 3 h driving each every Saturday and Sunday. This questionnaire consisted of age, history of motorcycle, type of motorcycle, survey on health status (age, present illness, and previous history of medication and hospitalization) and Japanese version of IIEF5, as described previously.6 Of the 244 motorcyclists, 10 men who were were <20 years of age or over 60 years were excluded from our analysis, leaving 234 who were evaluable motorcyclists. Of the 234 men, 113 had chronic diseases as follows: lumbar pain in 72 patients (31%), hemorrhoid in 29 (12%), hypertension in 17 (7%), diabetes mellitus in 10 (4%) and other diseases in six (3%). Of the 113 men, 17 had more than one disease. There were no men who had coronary artery disease and hyperlipidemia. Erectile dysfunction was diagnosed when the IIEF5 score was <22.7 The 5-items version of the International Index of Erectile Function was given to 2311 men who were employees of 10 pharmaceutical companies with head offices in Tokyo, Kyoto or Osaka, and fathers of employees in the health status survey. The questionnaire consisted of the Japanese version of IIEF5 and survey on health status (age, present illness, previous history of medication, hospitalization and surgical history) between December 1997 and September 1999. The questionnaires were self-administered in their homes and no attempt was made to validate the responder's answers. Of the 2311 men, 1517 men responded to the questionnaire completely (response rate 65.6%). Of the 1517 men, the 752 healthy controls whose age ranged from 22 to 59 years and had no history of present or previous illness were subjects.
We evaluated the prevalence of ED by the IIEF5 score in each age group (20–29, 30–39, 40–49, 50–59 and over 60 years). The severity of ED was classified into five categories in each age group (non-ED: IIEF5>22, mild: 17–21, mild-moderate: 12–16, moderate: 8–11, severe: IIEF<7).7 They were also classified into subgroups according to type of motorcycle (hard-padded and soft-padded saddle) and motorcycling history (over 10 years and <10 years). The prevalences of ED and IIEF5 were compared in the subgroups.
Prevalence and severity of ED were compared between motorcyclists and healthy controls using χ2 test, Mann–Whitney U-test and one-way analysis of variance (ANOVA). Log-likelihood stepwise logistic regression analysis was performed to determine the independent risk factors of ED. All statistical analysis was performed using SPSS version 11 (SPSS Inc., Chicago, IL, USA). Statistical significance was set at P<0.05 in all analyses.
Table 1 shows the characteristics of the 234 motorcyclists and 752 healthy controls. There were no significant differences for the means of IIEF5 and ages between the motorcyclists and healthy controls.
Erectile dysfunction severity in controls and motorcyclists is shown in Table 2. By one-way ANOVA analysis, the severity of ED was associated with age (P=0.008). In motorcyclists, the prevalence of mild and mild-to-moderate ED was significantly higher (P<0.0001, respectively) than in controls in each age group. However, in the 20–29 and 30–39 age groups, the prevalence of moderate ED was significantly lower in motorcyclists than in controls (P=0.0003 and 0.003, respectively).
Of the 122 motorcyclists who had a history of 10 or over 10 years motorcycling, 73% (89/122) had ED, compared to 64% (72/112) motorcyclists with ED, who had a history of <10 years. There was no significant difference in the prevalence of ED between the motorcyclists with 10 or over 10 years motorcycling history and those with a history of <10 years. Of the 178 motorcyclists with hard-padded saddle, 124 (70%) had ED. Conversely, of the 32 motorcyclists with soft-padded saddle, 20 (63%) had ED. There were no significant differences in the prevalence of ED and IIEF5 between the hard-padded and soft-padded saddle groups.
In motorcyclists with or without chronic diseases, the prevalences of ED were 67% (76/113) and 70% (85/121), respectively (P=0.673). Motorcyclists without lumbar pain had ED in 73% of cases (119/162), while motorcyclists with lumbar pain had ED in 58% (42/72) (P=0.021). In the remaining diseases, there was no significant difference in the prevalence of ED.
On log likelihood stepwise logistic regression analysis, motorcycling and age were independent risk factors of ED (Table 3). Motorcycling was the strongest risk factor, on the basis of its odds ratio (OR) of 5.5 (95% confidence interval (CI) 3.7–8.1), followed by age 50 years or older (OR 2.1, 95% CI 1.3–3.3).
Several investigators had reported the relationship between bicycling and ED.2, 8, 9 However, there had been no report on the relationship between motorcycling and ED. In the present study, the relationship between motorcycling and ED was revealed in a questionnaire-based study.
Motorcycling was the stronger risk factor for ED when compared to age, based on logistic regression analysis. The severity of ED in motorcyclists, however, was not so severe when compared to those in control. More than half of the motorcyclists had mild or mild-to-moderate ED. The high prevalence of mild or mild-to-moderate ED might be related to the cause of ED in motorcyclists. In the current study, however, the limitation was that the data collection was limited to self-report. Medical conditions that might be asymptomatic are often unknown to the subject, and are consequently under-reported. In addition, we have no data of the factors that might affect the occurrence of ED, such as body mass index and the habit of smoking. These factors may affect the difference in the severity of ED between the motorcyclists and controls.
In cyclists, the cause of ED is associated with the blood supply to the penis. Penile systolic pressure and tissue oxygen tension of glans penis reduced to around 60% of the baseline after sitting on a bicycle saddle, and recovered to normal after a 10-min period.10, 11 In addition, ED in cyclists is also associated with the saddle design.12 The saddle design of a wide medium-padded seat without saddle nose was the least decrease of penile oxygen pressure, compared to the traditional saddle (narrow heavily padded seat) as well as a wide unpadded seat. Therefore, we investigated the relationship between ED and saddle design in motorcyclists. There was no apparent relationship between the saddle design and prevalence of ED; however, although not statistically significant, the prevalence of ED did tend to increase in motorcyclists with the hard-padded saddle. Further study with a larger number is necessary to determine whether this association will be significant.
The vibration exposure of traffic police motorcyclists was reported to be a risk factor for the development of hand–arm vibration syndrome.13 The vibration causes disruption of retrograde axoplasmic transport in the peripheral nerve.14 The vibrational energy causes extracellular signal-regulated kinase (ERK) activation and endothelin-1 (ET-1) production.15 In ED patients, plasma levels of ET-1 are elevated, and are associated with reduction in growth hormone (GH), nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) in systematic and cavernous blood.16 The vibration to perineal lesion from the saddle in motorcycle riding may cause peripheral nervous damage and the elevation of plasma levels of ET-1, and reduction in GH, NO and cGMP in the cavernous blood. Therefore, the vibration from motorbike may cause ED, and the degree of vibration to perineal lesion might be associated with the severity of ED. In the current study, most of the motorcyclists used the hard-padded saddle that might give stronger vibration to the perineal lesion, as well as more directly compared to the soft-padded saddle. Although there were no significant differences in the prevalence of ED and IIEF5 score between the hard-padded and soft-padded saddle groups because of the small material with soft-padded saddle, the prevalence of ED did tend to increase in motorcyclists with the hard-padded saddle. Further studies are necessary to determine the cause of ED in motorcyclists.
The results of the present study demonstrated that motorcycling was one of the risk factors for ED, and that most of the motorcyclists with ED were classified as mild and mild-to-moderate. The current study was a preliminary study and the data for the current study were obtained by self-report of the subjects. Additional studies are needed for the cause of ED in motorcyclists.
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Ochiai, A., Naya, Y., Soh, J. et al. Do motorcyclists have erectile dysfunction? A preliminary study. Int J Impot Res 18, 396–399 (2006) doi:10.1038/sj.ijir.3901445
- erectile dysfunction
- Japanese male
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