Purpose: We identified factors that affect sexual function in men 50 to 80 years old and, therefore, may confound the comparison among groups of elderly men. In particular, we identified factors that may influence a comparison between prostate cancer patients and the general population, or confound the relationship when comparing subgroups of patients in nonrandomized studies.
Materials and methods: A questionnaire, including the Radiumhemmet Scale of Sexual Function and modules assessing potential risk factors for waning sexual function, was sent to 431 patients 50 to 80 years old with prostate cancer diagnosed 1.5 to 2 years previously in the Stockholm area (Sweden) and a reference group of 435 age matched randomly selected men.
Results: Factors associated with physiological impotence included prostate cancer (relative risk 1.9), diabetes mellitus (relative risk 2.3), myocardial infarction (relative risk 1.5), medication with diuretics (relative risk 1.5), hydrogen blockers (relative risk 2.3) and warfarin type anticoagulants (relative risk 1.7). Patients treated for prostate cancer were more likely to be physiologically impotent compared to those with no initial treatment, and this was true for all treatment protocols after adjustment for confounding factors. Men treated with radical prostatectomy were more likely to be physiologically impotent than men treated with external beam radiation therapy (relative risk 1.5).
Conclusions: Waning sexual function in the prostate cancer patients was largely due to side effects of the treatment and this could not be explained by confounding factors. In particular, confounding could not explain the greater risk of impotence after radical prostatectomy compared to external beam radiation therapy.