Penile and finger sensory thresholds in young, aging, and diabetic males

To investigate the possible role of sensory function in conditions affecting sexual function, sensory thresholds were compared between young healthy men (n = 14, means age = 29.8), aging men (n = 15, means age = 67.3), and men suffering from diabetic impotence (n = 15, means age = 45.0). Using the psychophysical method of forced choice, vibrotactile and electrical stimulation thresholds were deterlmined in two separate sessions at two body sites: the fingertip and the ventral surface of the penis, just proximal to the glans. Vibrotactile penile thresholds (VTP) were lowest for young (Y) subjects and much higher for both aging (A) and diabetic (D) subjects. Electrical stimulation of the penis (ESP) showed the same trends, although the differences only approached significance (p = 0.06). The vibrotactile finger threshold (VTF) was significantly higher for A subjects as compared with Y and D subjects, but there was no difference between the Y and D groups. Diabetic patients had significantly higher thresholds for electrical stimulation of the finger (ESF), in contrast to the VTF finding. Finger thresholds were significantly lower than penile thresholds for all groups, and the change in threshold from finger to penis was greater in both aging and diabetic than in young subjects. Age was positively correlated with thresholds for ESF, ESP, VTF, and marginally for VTP when all three groups were analyzed together. However, in general the results of threshold determinations could not be attributed merely to age. Based on a detailed questionnaire of sexuality, VTP was negatively correlated with sexual activity and both ESP and VTP were negatively correlated with erectile capacity. The data are consistent with a genital sensory role for age-related and diabetic changes in sexual function.