Introduction: The relationship between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) have received increased attention recently because both diseases are highly prevalent, frequently co-associate in the same aging male group, and contribute significantly to the overall quality of life. The association between these two diseases has also garnered attention as investigators have hypothesized a common pathophysiology to explain the assertion that they are causally linked.
Methods: A causal association between LUTS and ED cannot be established on the basis of the ever-increasing number of epidemiological studies. Attempting to explain a causal relationship between ED and LUTS needs to be examined using Hill's criterion, which is used by many epidemiologists to separate causal from non-causal explanations.
Results: Given the epidemiological components of the Hill's Causality method, it is clear that there is a strong strength of association, internal consistency, and dose response effects between ED and LUTS. Because of the strong cross-sectional flavor to the epidemiological studies, the temporal relationships between ED and LUTS remain unknown. The issue of an "alternate explanation" to describe the LUTS-ED association appears to be accounted for in that several large studies have provided convincing multiple regression analyses in which the ED-LUTS relationship remains significant. The link between ED and LUTS has biologic plausibility given the four leading theories of how these diseases interrelate. These explanations fall into four theories each with a variable amount of supporting data. These include: (1) NOS/NO levels decreased or altered in the prostate and penile smooth muscle, (2) Autonomic hyperactivity effects on LUTS, prostate growth and ED., (3) increased Rho-kinase activation/endothelin activity, and (4) prostate and penile ischemia.
Conclusions: LUTS and sexual dysfunction are highly prevalent in aging men. Both conditions are also significant contributors to overall quality of life. New data has emerged to indicate potential links in epidemiological, physiologic, pathophysiologic and treatment aspects of these two entities.