The normative characteristics of nocturnal penile tumescence (NPT) in a group of 20- to 26-year-old men were measured during continuous all-night recordings. Each penile erection during the night was recorded and compared with periods of (REM) activity during sleep. Subjects averaged 4.22 erection episodes per night which averaged 32.66 minutes, with 91.4% of all tumescence episodes occurring, at least in part, during a REM period. Tumescence was categorized into four types depending upon degree and upon presence or absence of the REM period. Maximum episodes during REM predominated. NPT was characterized as a multiple-function phenomenon which may serve to stimulate and develop the psychosexual association areas of the cortex during childhood and to maintain these areas during adulthood. The norms presented should have clinical utility in the diagnosis and prognosis of impotence.
Karacan I, Hursch CJ, Williams RL, Thornby JI. Some Characteristics of Nocturnal Penile Tumescence in Young Adults. Arch Gen Psychiatry. 1972;26(4):351-356. doi:10.1001/archpsyc.1972.01750220061011