Aspects of sexual satisfaction in men with erectile dysfunction: a factor analytic and logistic regression approach

The International Index of Erectile Function (IIEF), Sexual Encounter Profile (SEP), and Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS) assess efficacy of phosphodiesterase type 5 (PDE5) inhibitor treatment of erectile dysfunction (ED).

To determine the degree that multiplicity of satisfaction questions in ED treatment evaluation instruments are congruent, to better understand the concept of sexual "satisfaction," and to identify factors that correlate with improvement.

Questionnaire data from 4,174 placebo- or tadalafil-treated patients with ED were analyzed. Principal component analysis (PCA) was performed on IIEF and SEP satisfaction questions. Spearman correlation coefficients were determined. Data from 431 of the 4,174 patients who completed EDITS questionnaires were analyzed. Logistic regression was used to investigate improvement of each IIEF satisfaction question.

PCA rotated on three factors explained 91% of total variance and separated IIEF Q6 (intercourse frequency) from a SEP and a remaining IIEF factor. All correlations between and among questions were close (rho = 0.62-0.98; P < 0.0001), except for those with IIEF Q6 (rho = 0.28-0.34; P < 0.0001). In a sub-sample, PCA of five IIEF, two SEP, and three EDITS questions identified four factors that explained 90% of all variance: EDITS questions, IIEF questions except Q6, SEP questions, and IIEF Q6. Greater improvement in IIEF-EF domain score was consistently and positively associated with satisfaction measures (P < 0.0001).

Factor analysis detected close relationships among satisfaction questions in IIEF, SEP, and EDITS instruments, each of which, apart from IIEF Q6 (intercourse frequency), appeared to be an independent measure of satisfaction. Cultural differences may explain different satisfaction correlations with baseline ED severity in different regions. Clinicians may make use of the correlation between intercourse frequency (Q6) and satisfaction when prescribing a PDE5 inhibitor for ED, by explaining that the inhibitor should enable more frequent intercourse.