Risk factors for erectile dysfunction in end-stage renal disease patients with short- or long-term hemodialysis therapy

As a result of improvement in HD therapy and small number of kidney transplantation due to extreme shortage of kidney donation in Japan, the number of both end-stage renal disease (ESRD) patients with long-term chronic HD therapy and patients who receive short period of chronic HD but have various comorbidities are gradually increasing [10]. Several cross-sectional studies revealed that ED is a very common disease in ESRD patients; however, the influence of long-term chronic HD for ED was not well evaluated. In this study, the frequency of ED was almost equivalent between short-term HD patients and long-term patients, and hyperuricemia was demonstrated to be an independent risk factor in not only all patients but also long-term hemodialysis patients.

Various physiological changes including secondary hyperparathyroidism and arteriosclerosis due to prolonged chronic hemodialysis are well-known to be getting worsen progressively [11]. ED status in ESRD patients with long-term chronic HD was predicted to be progressed; however, long-term chronic HD did not appear to deteriorate ED status under adjustment of various factors. This is a cross-sectional study based on questionnaire and we could not include various clinical factors such as high-intact parathyroid hormone level, zinc deficiency, evaluation of malnutrition status, and degree of arteriosclerosis. Among these parameters, degree of arteriosclerosis might not be advanced in ESRD patients with long-term HD as strong as we suspected because the number of past history of CVD in patients with long-term HD was not larger than those in patient with short-term HD even though they had long duration of chronic kidney disease. Prospective cohort study which assess progression of ED status according to prolongation of hemodialysis period and include various clinical factors which are mentioned above might be more eligible to assess whether long-term HD affect ED severity or not.

Hyperuricemia was well-known as a risk factor for various vascular complications such as stroke, coronary disease, heart failure, and chronic kidney disease [12–15]. ED is closely associated with endothelial dysfunction and CVD, and the relationship between coronary artery disease and high uric acid level was reported [16]. On the other hand, inverse correlation between uric acid levels and all causes and CVD mortality in HD population was reported in contrast to the association of hyperuricemia and CVD risk in general population [17]. While the possibilities of surrogate for a better nutritional status and antioxidative properties of uric acid were pointed out, the potential mechanisms of this association in HD patients still remain uncertain[17, 18]. This cardioprotective mechanism of hyperuricemia in HD population might contribute to lower frequency of ED.

There are various considerations in this study that limit our findings. First, this is a relatively small sample size cross-sectional study. Second, we enrolled only patients who accepted our proposal and filled out the questionnaire so that we could not reflect information on patients who refused to participate or excluded from the study cohort. Third, IIEF-5 based on self-reporting was the only tool to evaluate ED in this study, and no other physical and diagnostic tests which evaluated not only ED status but also pathogenesis factors. Last, we could not assess influence of variables which have been reported to be linked to ED, such as autonomic neuropathy, residual renal function, hormonal status, anemia, secondary hyperparathyroidism, zinc deficiency, and so on. Prospective large cohort study including various clinical factors as mentioned above will be needed to address this subject.