Inclusion Criteria:  Healthy volunteer without (a history of) erectile dysfunction Male Aged 18 - 29 years  Exclusion Criteria:  Test subjects who are unwilling to sign informed consent Test subjects with erectile dysfunction IIEF-5 score of below 17 (History of) sickle cell aneamia, atherosclerosis and diabetes type I or II. (History of) REM-sleep behavior disorder or other sleep disorders such as restless legs syndrome, insomnia, and sleep apnea Usage of sleeping pills or benzodiazepines.