The relationship of chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) with erectile dysfunction has been investigated in a few studies. However, previous studies are limited by having a small participant number and minimal adjustment for potential confounding factors including testosterone and metabolic syndrome. Therefore, the current data are insufficient to support routine screening of erectile dysfunction in men with CP/CPPS or CP/CPPS in men with erectile dysfunction. This study aims to evaluate the relationship between erectile dysfunction and CP/CPPS.

A prospective cross-sectional study was conducted that included 8,261 men who had participated in a health examination. The participants were applicants. Only applicants over 40 years of age were allowed to participate in medical examinations. Medical histories were collected using a standardized structured questionnaire. All of the participants provided written informed consent, and data concerning the participants were collected prospectively. 
 The National Institutes of Health-Chronic Prostatitis Symptom Index (NIH-CPSI), and the International Index of Erectile Function-5 (IIEF) were used for assessment of symptoms. Symptoms were classified as a “mild prostatitis-like symptom” if respondents reported perineal or ejaculatory pain and had a NIH-CPSI pain score of ≥4 and <8; the symptoms were classified as moderate to severe if the pain score was ≥8 according to previous reports. Moderate to severe erectile dysfunction was defined as IIEF <12. 
 Two blood pressure (mm Hg) measurements, obtained 5 minutes apart, were averaged using a mercury sphygmomanometer on the right arm. Waist circumference (cm), to the nearest 0.1 cm, was measured midway between the lowest rib and the iliac. Body weight (kg) and body height (cm) were also recorded. Serum was collected in the morning (between 7:00 and 9:00 am) after an overnight fast. The biochemical analyses included the fasting serum glucose level, the triglyceride level, and the high-density lipoprotein cholesterol level. A diagnosis of metabolic syndrome was made if three or more of the National Cholesterol Education Program-Adult Treatment Panel III criteria were satisfied.
 Serum testosterone was measured via radioimmunoassay using a kit from Cisbio Bioassays, Inc. (Parc Marcel Boiteux, Codolet, France). The intra-assay coefficients of variation for all of the assays were less than 9%, and the inter-assay coefficients of variation were less than 12%. For each assay, all samples from each subject were measured in the same assay run.
 We then investigated the relationship using the Spearman correlation test, multiple linear regression, and logistic regression analyses.

The mean age was 50.4 ± 5.5 years. The mean testosterone level was 613 ng/dL (21.3 nmol/L), and 3,258 (36.8%) men had metabolic syndrome. In total, 2,205 (24.9%) men had prostatitis-like symptoms (NIH-CPSI pain score of ≥4 and perineal or ejaculatory pain), and 618 (7.0%) men had moderate to severe symptoms (NIHCPSI pain score of ≥8). Additionally, 1,041 men (12.6%) were classified as demonstrating moderate to severe erectile dysfunction (IIEF < 12). The IIEF score was found to have a significant negative correlation with the NIH-CPSI pain domain score (correlation coefficient = -0.198; P < 0.001). After adjusting for age, metabolic syndrome status, and testosterone level, there was no change in the negative correlation between the NIH-CPSI pain domain score and IIEF score (Beta = -0.395; P < 0.001). After adjusting for age, testosterone level, and metabolic syndrome, the odds ratio (OR) for moderate to severe erectile dysfunction significantly increased with the severity of pelvic pain (mild prostatitis-like symptoms, OR for moderate to severe erectile dysfunction: 2.557, 95% confidence interval: 2.092–3.125; moderate to severe symptoms, OR for moderate to severe erectile dysfunction: 5.164: 95% confidence interval: 4.433–6.016).

Erectile dysfunction and chronic prostatitis-like symptoms are significantly and independently correlated with each other. The severity of prostatitis-like symptoms is also related to erectile dysfunction.

Based on our data, we suggest routine screening for CP/CPPS in men with erectile dysfunction and erectile dysfunction in men with CP/CPPS.