Nocturnal penile tumescence (NPT) studies are commonly used in the assessment of sexual dysfunction in diabetic men. While much of the evidence in favor of its use has come from the observation of markedly abnormal NPT in impotent diabetic men, little research has focused on the quality of nocturnal erections in sexually functional diabetics. Ten diabetic men who reported normal daytime sexual function were studied with 4 nights of polysomnography, including NPT assessment. They had significantly diminished NPT profiles when compared with that of an agematched, nondiabetic, healthy control group. Without controlling for the effect of diabetes on NPT, between 70% and 90% of sexually functional diabetics had NPT profiles in a range that would be classified as indicative of organic sexual dysfunction for a man presenting for evaluation of sexual dysfunction. The finding of NPT abnormalities in a diabetic man should not be taken as evidence for irreversible sexual dysfunction. Rather, the condition of diabetes appears to result in NPT abnormalities, regardless of the adequacy of daytime sexual function.
(Arch Intern Med. 1992;152:114-118)