Erectile dysfunction (ED) is prevalent in middle-aged and older men and can significantly decrease their quality of life. The incidence of ED increased by aging, smoking, metabolic syndrome, lifestyle diseases, and mental status. Decreased physical activity is also known as the risk factor of ED. The benefits of aerobic exercise with a treadmill or bicycle ergometer have been shown in randomized trials for men with ED. Aerobic exercise increases nitric oxide, which is involved in vasodilation in the penile vessels and improves penile rigidity. In addition, the treadmill and bicycle ergometer improve muscle strength, balance, and flexibility of lower limbs, which is related with gait function. However, no previous study determined the association of ED with gait function. Therefore, we hypothesized the gait function may be related with ED. We aimed to investigate the relationship ED and gait function in a community-dwelling population.
We cross-sectionally analyzed 324 men who underwent frailty screening1 in the Iwaki Health Promotion Project in 2015 in Hirosaki, Japan. ED was assessed with the 5-item International Index of Erectile Function (IIEF-5). The participants were divided into two groups: the low-IIEF-5 (≤16) and high-IIEF-5 (>16). We evaluated physical function, including gait function and grip strength. Gait function was evaluated by the two-step score (the ratio of the maximum length of two strides to height, Figure 1). The two-step score was initially designed to measure balance, flexibility, and muscle strength of the lower limb and is used in Japan to assess individual risk of reduced mobility.2 We assessed daily physical activity, comorbidities, mental status, and laboratory data. The association of physical function and a low-IIEF-5 were analyzed by multivariate logistic regression analysis.
Of 324 men, 154 (48%) had a low-IIEF-5. The two-step score in the low-IIEF-5 group was significantly inferior to those in the high-IIEF-5 group (1.53 vs. 1.66, P <0.001). Multivariate analysis showed that the two-step score (odds ratio = 0.08), age, and total testosterone were independently associated with a low-IIEF-5.3
Our findings suggest that men with a lower two-step score had a higher incidence of having worse symptoms of erectile function. A previous study conducted in Korea reported that reduced grip strength had significantly contributed to moderate to severe ED.4 Indeed, men with a low-IIEF-5 had a significantly lower grip strength than with a high-IIEF-5 in this study (37.6 vs. 41.4kg, P <0.001). However, grip strength was not independently associated with ED in this study. Conversely, the two-step score had a higher impact on ED than grip strength. The difference between the grip strength and two-step test was an evaluation of comprehensive function of lower limbs, such as a maximum function of balance, flexibility, and muscle strength. This result suggested that low muscle strength alone is not enough to estimate the presence of ED. Moreover, a longer stride requires much more movement of pelvic muscle and ankle joint, which is thought to relate with pelvic floor muscles. In men, contraction of the pelvic ﬂoor muscles helps to maintain penile rigidity by preventing venous return.5 We speculated the risk of ED in men with low two-step scores might result from weakness of the pelvic ﬂoor muscles.
Because we could not clarify the causal relationship between gait function and erectile function in this study, our future research should investigate whether enhancing gait function can lead to improving erectile function. In conclusion, gait function measured by the two-step score was independently associated with ED.
Fig. 1: Two-step score: the ratio of the maximum length of two strides to height.
Written by: Teppei Okamoto, MD, PhD and Shingo Hatakeyama MD, PhD, Department of Urology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.
1. Soma O, Hatakeyama S, Okamoto T et al. Multicenter prospective study validating the efficacy of a quantitative assessment tool for frailty in patients with urological cancers. Med Oncol. 2019; 36: 88.
2. Muranaga S, Hirano K. Development of a convenient way to predictability to walk, using a two-step test. J Showa Med Assoc 2003; 63: 301-8.
3. Okamoto T, Hatakeyama S, Imai A et al. The Relationship Between Gait Function and Erectile Dysfunction: Results from a Community-Based Cross-Sectional Study in Japan. J Sex Med. 2019.
4. Chung HS, Shin MH, Park K. Association between hand-grip strength and erectile dysfunction in older men. Aging Male. 2018; 21: 225-30.
5. Silva AB, Sousa N, Azevedo LF, Martins C. Physical activity and exercise for erectile dysfunction: systematic review and meta-analysis. Br J Sports Med. 2017; 51: 1419-24.