Exercise is Associated with Better Erectile Function in Men Under 40 as Evaluated by the International Index of Erectile Function

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ORIGINAL RESEARCH—ANATOMY/PHYSIOLOGY Exercise is Associated with Better Erectile Function in Men Under 40 as Evaluated by the International Index of Erectile Function jsm_2560

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Wayland Hsiao, MD, Adam B. Shrewsberry, MD, Kelvin A. Moses, MD, PhD, Timothy V. Johnson, MD, Amanda W. Cai, BA, Peter Stuhldreher, MD, Beau Dusseault, MD, and Chad W.M. Ritenour, MD Department of Urology, Emory University, Men’s Health Center, Atlanta, Georgia, USA DOI: 10.1111/j.1743-6109.2011.02560.x

ABSTRACT

Introduction. Studies have shown an association between erectile dysfunction and sedentary lifestyle in middle-aged men, with a direct correlation between increased physical activity and improved erectile function. Whether or not this relationship is present in young, healthy men has yet to be demonstrated. Aim. The aim of this study was to assess the association between physical activity and erectile function in young, healthy men. Main Outcome Measures. The primary end points for our study were: (i) differences in baseline scores of greater than one point per question for the International Index of Erectile Function (IIEF); (ii) differences in baseline scores of greater than one point per question for each domain of the IIEF; (iii) exercise energy expenditure; and (iv) predictors of dysfunction as seen on the IIEF. Methods. The participants were men between the ages of 18 and 40 years old at an academic urology practice. Patients self-administered the Paffenbarger Physical Activity Questionnaire and the IIEF. Patients were stratified by physical activity into two groups: a sedentary group (ⱕ1,400 calories/week) and an active group (>1,400 calories/ week). Men presenting for the primary reason of erectile dysfunction or Peyronie’s disease were excluded. Results. Seventy-eight patients had complete information in this study: 27 patients (34.6%) in the sedentary group (ⱕ1,400 kcal/week) and 51 patients (65.4%) in the active group (>1,400 kcal/week). Sedentary lifestyle was associated with increased dysfunction in the following domains of the IIEF: erectile function (44.4% vs. 21.6%, P = 0.04), orgasm function (44.4% vs. 17.7%, P = 0.01), intercourse satisfaction (59.3% vs. 35.3%, P = 0.04), and overall satisfaction (63.0% vs. 35.3%, P = 0.02). There was a trend toward more dysfunction in the sedentary group for total score on the IIEF (44.4% vs. 23.5%, P = 0.057), while sexual desire domain scores were similar in both groups (51.9% vs. 41.2%, P = 0.37). Conclusions. We have demonstrated that increased physical activity is associated with better sexual function measured by a validated questionnaire in a young, healthy population. Further studies are needed on the long-term effects of exercise, or lack thereof, on erectile function as these men age. Hsiao W, Shrewsberry AB, Moses KA, Johnson TV, Cai AW, Stuhldreher P, Dusseault B, and Ritenour CWM. Exercise is associated with better erectile function in men under 40 as evaluated by the international index of erectile function. J Sex Med 2012;9:524–530. Key Words. Erectile Dysfunction; Exercise; Young Men; Physical Activity

Introduction

E

rectile dysfunction (ED) is a persistent inability to attain and maintain an erection sufficient to permit satisfactory sexual performance [1]. Lifestyle choices, such as smoking, diet, alcohol

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consumption, and obesity are known to affect erectile function (EF) [2–4]. Recently, there has been increased interest in the relationship between exercise and ED [5,6]. Such a relationship is important because exercise may be an important modifiable risk factor for ED. © 2011 International Society for Sexual Medicine

Exercise and ED in Young Men The relationship between exercise and EF has been evaluated in a number of studies. An association between ED and sedentary lifestyle (defined as less than 200 kcal exercise energy expenditure per day) was demonstrated in the Massachusetts Male Aging Study [4] and the Androx Vienna Municipality Study [7]. In addition, exercise was demonstrated to be a modifiable risk factor. Men who increased exercise in midlife decreased their risk of ED by 70% [4,8]. Esposito et al. also showed that exercise and weight loss can improve EF in a group of sedentary obese men with low baseline EF [2]. There remains, however, uncertainty as to how much exercise is needed to maintain good EF. For general health, the American College of Sports Medicine and the American Heart Association issued guidelines in 2007 suggesting 30 minutes of moderate activity five times a week or 20 minutes of vigorous activity three times a week for overall good health [9]. In 2008, the CDC released guidelines suggesting 150 minutes of moderate aerobic activity a week, 75 minutes of intense aerobic activity a week, or an equivalent mix of moderate and intense aerobic activity all with 2 days of muscle strengthening exercises [10]. No such exercise guidelines exist for good EF. While exercise certainly affects EF in older men with suboptimal baseline EF and with increased medical comorbidity, the question remains unanswered as to whether exercise is associated with better EF in healthy, young men. We hypothesized that increased physical activity is associated with better EF, even in young men. To test this hypothesis, we used validated surveys of both EF (the International Index of Erectile Function [IIEF]) and physical activity (Paffenbarger) and used an activity level average of 200 kcal per day to distinguish between sedentary and active lifestyle. The IIEF is the gold standard questionnaire in the evaluation of ED introduced by Rosen et al. in 1997 [11]. The Paffenbarger Physical Activity Questionnaire is a survey of exercise energy expenditure and has been associated with overall mortality and cardiac mortality [12–14]. Methods and Materials

Patients After Institutional Review Board approval was granted for this study, we enrolled patients presenting to our urology clinic between the ages of 18 and 40 years old. Any patient who presented with a primary complaint or diagnosis of ED or Peyronie’s

525 disease was excluded from this study. After informed consent was obtained, patients self-administered two surveys: the Paffenbarger Physical Activity Questionnaire and the IIEF. Patient records were reviewed for medical history and demographic information. Additionally, medical data such as height, weight, and blood pressure were obtained.

Physical Activity Outcomes The Paffenbarger Physical Activity Questionnaire was used to evaluate exercise energy expenditure [12]. In this validated survey, patient-reported physical activity is translated into total weekly energy expenditure (measured in kilocalories per week). The Paffenbarger is divided into four types of energy expenditure: stairclimbing, walking, light sport/recreational activity, and vigorous sport/ recreational activity. Each category is given a corresponding energy equivalent. “Light sports” included activities such as golf, yard work, weight lifting, hiking, and kickball. “Vigorous sports” included activities such as swimming, basketball, tennis, cycling, running, and boxing. Physical activity scoring was then performed based on the following calculations: 8 kcal per block walked, 8 kcal per 20 stairs climbed, 5 kcal per minute “light activity,” and 10 kcal per minute “vigorous activity.” Based on an estimation of 20 minutes of moderate aerobic activity per day, a threshold of 200 kcal per day of exercise energy expenditure was used to stratify patients into a “sedentary” group (ⱕ1,400 kcal/ week) and an “active” group (>1,400 kcal/week). Sexual Outcomes The IIEF is a well-known, 15-question validated tool for measurement of EF [11]. There are five domains of the IIEF (EF, orgasm function, sexual desire, intercourse satisfaction, and overall satisfaction) and a maximum total score of 75. Because of the lack of a normal distribution of IIEF score, patients were divided into those with sexual dysfunction vs. those without sexual dysfunction based on scores. For the total score, patients were divided into >60 (no dysfunction) vs. ⱕ60 (dysfunction), which assumed that sexual dysfunction meant a greater than one point deficit on each question asked when averaged across all 15 questions. For the EF domain (maximum score of 30), patients were divided into those >25 (no dysfunction) vs. those ⱕ25 (erectile dysfunction). For the orgasmic domain, which has a maximum value of 10, patients were divided into 9–10 (no dysfunction) vs. <9 (dysfunction). For the sexual desire domain, which also has a maximum value of 10, J Sex Med 2012;9:524–530

526 patients were divided into 9–10 (no dysfunction) vs. <9 (dysfunction). For the intercourse satisfaction domain, patients were divided into 13–15 (no dysfunction) vs. <13 (dysfunction). For the overall satisfaction domain, patients were divided into 9–10 (no dysfunction) vs. <9 (dysfunction).

Primary End Points The primary end points for our study were: (i) differences in baseline scores of greater than one point per question for total score of the IIEF; (ii) differences in baseline scores of greater than one point per question for each domain of the IIEF; (iii) exercise energy expenditure; and (iv) predictors of dysfunction as seen on the IIEF. Statistical Analysis Patients were stratified by physical activity into two groups: a sedentary group (ⱕ1,400 calories/ week) and an active group (>1,400 calories/week). A Shapiro–Wilk test was performed to verify the nonnormal distribution of IIEF scores. One-way analysis of variance was used to compare means. Pearson chi-square tests and Fisher’s exact test were used to compare categorical variables. Fisher’s exact test was performed if there were less than five subjects in a given categorical variable. All tests were two-sided except for one instance in which there were zero patients in only one of the comparison groups. A nominal logistic regression model was performed for any degree of sexual dysfunction as measured by the IIEF domains. The model was repeated for each domain of the IIEF as well as for the total score. Included in this model were body mass index (BMI), smoking status, exercise level, hypertension, cycling, and age. All statistical analysis was performed with JMP (SAS Institute, Cary, NC, USA) and SPSS 16.0 (SPSS Inc, Chicago IL, USA). Results

Baseline Characteristics Seventy-eight patients had complete information in this study: 27 patients (34.6%) in the sedentary group (ⱕ1,400 kcal/week) and 51 patients (65.4%) in the active group (>1,400 kcal/week). The two groups were similar in age, racial demographic, BMI, as well as baseline blood pressure (P > 0.05 for all) (Table 1). No patients in our study reported any history of coronary artery disease, peripheral vascular disease, or beta-blocker use. There was a higher prevalence of diabetes mellitus in the sedentary group (11.1% vs. 0%, P = 0.038). While J Sex Med 2012;9:524–530

Hsiao et al. Table 1

Baseline characteristics

Variable

Sedentary N = 27

Exercise N = 51

Age (years)—mean (SD) 33.1 (5.0) 31.5 (6.6) Race White 16 (59.3%) 40 (78.4%) Non-white 11 (40.7%) 11 (21.6%) 27.2 (3.9) 26.0 (4.0) BMI (kg/m2)—mean (SD) Systolic blood pressure 128.4 (13.6) 126.6 (12.2) (mm Hg)—mean (SD) Diastolic blood pressure 81.0 (9.8) 78.4 (7.2) (mm Hg)—mean (SD) Subjective health Smoker* 4 (14.8%) 2 (3.9%) 3 (11.1%) 0 (0%) Diabetes mellitus† Hypertension* 4 (14.8%) 4 (7.8%) Previous pelvic trauma* 2 (7.4%) 2 (3.9%) Coronary artery disease 0 (0%) 0 (0%) Peripheral vascular 0 (0%) 0 (0%) disease Beta-blocker use 0 (0%) 0 (0%)

P value 0.230 0.075 0.198 0.573 0.236

0.17 0.038 0.44 0.61 1.000 1.000 1.000

These are the baseline characteristics of our study group stratified by physical activity. There were no differences in age, BMI, or blood pressure. There were three diabetic men in the sedentary group, while there were none in the active group *Fisher’s exact test, two-tail †Fisher’s exact test, one-tail

histories of smoking (14.8% vs. 3.9%, P = 0.17) and pelvic trauma (7.4% vs. 3.9%, P = 0.61) were higher in the sedentary group, these differences did not reach statistical significance.

Sexual Outcomes and Exercise The mean total IIEF score for all patients was 62.4 (⫾16.0) with domain scores as follows: EF 25.6 (⫾7.6); orgasm function 8.8 (⫾2.3), sexual desire 8.4 (⫾2.0), intercourse satisfaction 11.5 (⫾4.3), and overall satisfaction 8.1 (⫾2.4). Because of nonGaussian distribution of IIEF scores (P = < 0.001 for all domains by Shapiro–Wilk test), all analysis was carried out in a dichotomized manner. There were higher rates of dysfunction in the sedentary group in the EF domain (44.4% vs. 21.6%, P = 0.04), orgasm function domain (44.4% vs. 17.7%, P = 0.01), intercourse satisfaction domain (59.3% vs. 35.3%, P = 0.04), and overall satisfaction domain (63.0% vs. 35.3%, P = 0.02) (Figure 1). There was a trend toward more dysfunction in the sedentary group in total score (44.4% vs. 23.5%, P = 0.057), but sexual desire domain scores were similar in both groups (51.9% vs. 41.2%, P = 0.36). In all domains, rates of dysfunction exceeding 40% were observed in the sedentary group. Multivariate Analysis Binary logistic regression for predictors of dysfunction controlling for exercise level, smoking

Exercise and ED in Young Men

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Figure 1 Percentage of patients with dysfunction by domain of the IIEF. Patients were subcategorized by weekly caloric expenditure into two groups: exercise (ⱖ1,400 kcal/week) and sedentary (<1,400 kcal/week). For each domain, dysfunction is defined as follows: total score ⱕ60 points, erectile function <26 points, orgasm function <9 points, sexual desire <9 points, intercourse satisfaction <13 points, and overall satisfaction <9 points.

status, cycling, age, BMI, and hypertension revealed that sedentary lifestyle was associated with an increased dysfunction in the EF domain (odds ratio [OR] 3.16, 95% confidence interval [CI] 1.02–9.86), orgasm function domain (OR 4.39, 95% CI 1.33–14.46), intercourse satisfaction domain (OR 2.98, 95% CI 1.05–8.50), overall satisfaction domain (OR 4.86, 95% CI 1.59–14.79), and total score ⱕ 60 (OR 3.16, 95% CI 1.02–9.86) (Table 2). Sedentary lifestyle did not predict sexual desire (OR 1.53, 95% CI 0.53–4.41). In all domains examined, smoking, cycling, age, BMI, or hypertension did not predict sexual function in this young population. Discussion

The scientific literature documents that exercise can positively affect sexual function in obese and older patients [2]. However, the relationship of sexual function and physical activity is less well studied in young, healthy men. In this study, we have shown an association of increased exercise with improved EF as well as higher rates of sexual dysfunction in sedentary young men as assessed by the IIEF. This relationship was still present after controlling for multiple confounding factors including age, BMI, smoking, hypertension, and cycling. Only exercise predicted sexual function in our population on multivariate analysis. This study obviously reports a small difference in EF in young men with a mean difference of only 3.1 points in the EF domain between sedentary

and exercising patients (23.6 vs. 26.7). While the clinical significance of this difference is debatable, it remains possible that this small difference at a young age may portend a further sexual deterioration in sedentary patients over time. Does a more sedentary lifestyle predict increased risk of developing ED in the future? Can exercise treat ED and perhaps modulate the natural course of ED in a young healthy population? The current literature shows that exercise can modify the severity of ED, but studies have only been done in men who already have manifested ED. Whether exercise alters the natural course or even prevents ED has yet to be shown [2]. This initial study is important in showing a small difference in patients as assessed by validated questionnaires at an early age. Knowledge that exercise early in life may modulate development of ED is important, such that patients can be evaluated and counseled appropriately. Recent data suggest that ED at a young age is highly correlated with increased cardiovascular morbidity [15]. In fact, a diagnosis of ED in men under 40 has been shown to increase the risk of ischemic heart disease, cardiac arrest, cerebrovascular disease, peripheral vascular disease, or coronary revascularization procedure with a higher standardized incidence ratio rate of 7.4–7.6 (a higher risk than that for men over 40 years old) when compared with a general population reference cohort [16]. Perhaps screening for ED at an early age could allow for earlier intervention with a recommendation of increased physical activity. It is possible that J Sex Med 2012;9:524–530

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0.20 (0.05–1.92)

0.97 (0.35–2.76)

0.63 (0.26–2.25)

(0.70–26.53) 0.11

(0.24–11.33) 0.62

0.52

0.75

0.85

0.37

0.14

0.04

0.20 (0.05–1.93)

0.32,1 (0.22–1.64)

0.59 (0.47–3.85)

(0.56–20.19) 0.18

(0.67–74.83) 0.10

0.42 (0.53–4.41

0.83 (0.12–5.67)

0.13 (0.76–9.06)

0.32 (0.16–1.82)

(0.52–22.22) 0.20

(0.30–13.72) 0.47

(1.33–14.46) 0.02

0.21

0.46

0.54

0.13

0.14

0.05

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We constructed multiple logistic regression models to predict sexual dysfunction and included exercise, cycling, age, BMI, and HTN. Only exercise significantly predicted IIEF scores in erectile function, orgasm function, intercourse satisfaction, overall satisfaction, and total score

0.21 (0.02–2.38)

0.46 (0.49–4.77)

0.54 (0.23–2.17)

(0.66–22.18) 0.13

(0.61–31.94) 0.14

0.047 (1.02–9.86) (1.59–14.79) 0.005

1.00 3.16 1.00 4.40 1.00 3.83 1.00 0.70 1.00 1.54 1.00 0.21

P value OR (95% CI) P value OR (95% CI)

1.00 4.86 1.00 1.64 1.00 4.31 1.00 0.76 1.00 0.98 1.00 0.30 1.00 2.98 (1.05–8.50) 1.00 5.53 (0.57–53.49) 1.00 2.16 (0.40–11.75) 1.00 1.11 (0.38–3.20) 1.00 1.18 (0.43–3.26) 1.00 0.57 (0.10–3.18)

P value OR (95% CI) P value OR (95% CI)

1.00 1.53 1.00 7.08 1.00 3.36 1.00 1.34 1.00 0.60 1.00 0.30 1.00 4.39 1.00 2.03 1.00 3.40 1.00 0.55 1.00 2.62 1.00 0.81

P value OR (95% CI) OR (95% CI) Term Variable

Erectile function

Exercise >1,400 1.00 (kcal/week) ⱕ1,400 3.16 (1.02–9.86) Smoking No 1.00 Yes 4.40 (0.61–31.9) Cycling No 1.00 Yes 3.83 (0.66–21.2) Age <30 1.00 ⱖ30 0.7 (0.23–2.2) BMI <25 1.00 ⱖ25 1.54 (0.50–4.77) HTN No 1.00 Yes 0.21 (0.02–2.38)

Table 2

Multivariate analysis.

Orgasm function

Sexual desire

Intercourse satisfaction

Overall satisfaction

Total score ⱕ 60

P value

Hsiao et al. early screening for ED may be a “gateway issue” to help motivate young men to have a long-term healthy lifestyle, which may also modulate the risk of diseases associated with sedentary lifestyle, including diabetes and cardiovascular disease among others. Screening for ED at an early age may be a window by which we can reach young men to espouse exercise and a healthy lifestyle. Of course, the mechanism for exercise-induced improvements in erections remains unknown, although possible mechanisms include improved vascular tone, better endothelial cell activation, increased release of neurotransmitters in the nervous system, or psychological benefits [17–20]. This study has several weaknesses, including the lack of testosterone levels, depression scores, and evaluation for psychogenic ED because all of these may be associated with EF in young men. Another weakness is the inability to control for diabetes. Eleven percent (3/27) of our sedentary group had diabetes, while no men in the active group had diabetes. Diabetes is an independent risk factor for ED [21]. Diabetes is also strongly associated with a sedentary lifestyle, however, and it is difficult to separate these two factors in our analysis. Our three diabetic patients had weekly exercise expenditures of approximately 110, 220, and 670 kcal of exercise per week making them both diabetic and sedentary. Because diabetes was not one of the formal exclusion criteria for our study, the patients were included in the final analysis. Another area of concern is the heterogeneity of our study population. While no patients were specifically presented with ED or Peyronie’s disease, there was no effort to control for presenting complaints between groups and patients presented with a variety of concerns, all in relatively small numbers. We plan to address this heterogeneity in future studies. The use of a urologic clinic population may limit our ability to determine the population prevalence of ED in the young population at large. However, we believe this is also a strength of our study because these are patients presenting to our urology practice for nonsexual concerns. Finally, some may question our definitions of function and dysfunction. While there is little literature to support such an exact cutoff, we feel that it is reasonable and similar to the cutoff widely employed for the EF domain of the IIEF. Conclusions

Physical activity has been demonstrated previously to be a modifiable risk factor for ED, specifically in

Exercise and ED in Young Men an older, obese population. Our study demonstrates an association between increased exercise and better EF in a young, healthy population. This emphasizes the importance of living a healthy, active lifestyle. Further study is needed to demonstrate the long-term effects of exercise or lack thereof on ED as these young, healthy men age. Corresponding Author: Chad W.M. Ritenour, MD, Department of Urology, Emory University, Men’s Health Center, 1365 Clifton Road NE, Building B, Atlanta 30322, Georgia, USA. Tel: 404-778-4898; Fax: 404-778-4006; E-mail: [email protected] Conflict of Interest: None.

Statement of Authorship

Category 1 (a) Conception and Design Wayland Hsiao; Beau Dusseault; Chad W.M. Ritenour (b) Acquisition of Data Wayland Hsiao; Adam B. Shrewsberry; Amanda W. Cai; Peter Stuhldreher (c) Analysis and Interpretation of Data Wayland Hsiao; Kelvin A. Moses; Timothy V. Johnson; Chad W.M. Ritenour

Category 2 (a) Drafting the Article Wayland Hsiao; Adam Shrewsberry; Timothy V. Johnson; Amanda W. Cai; Peter Stuhldreher; Beau Dusseault (b) Revising It for Intellectual Content Wayland Hsiao; Kelvin A. Moses; Timothy V. Johnson; Chad W.M. Ritenour

Category 3 (a) Final Approval of the Completed Article Wayland Hsiao; Adam Shrewsberry; Kelvin A. Moses; Timothy V. Johnson; Amanda W. Cai; Peter Stuhldreher; Beau Dusseault; Chad W.M. Ritenour

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