Relationship between sleeping posture and fluctuations in nocturnal scrotal temperature

Elevated testicular temperatures are a potential risk factor for impaired spermatogenesis and reduced semen quality. The development of portable devices for the measurement of scrotal temperatures closely correlating with testicular temperature offered the opportunity to identify periods with high scrotal temperatures during daily life. Notably, sleeping periods covering approximately 1/3 of the day are associated with increased scrotal temperatures to around 36 degrees C. Combining infrared video taping with scrotal temperature profiling, our study clarified that sudden drops of scrotal temperature during sleep are the consequence of changes of posture. Nocturnal scrotal temperatures were significantly higher during sleeping on the side compared with periods lying on the back (+0.65 degrees C, right scrotum, P<0.001; +0.54 degrees C, left scrotum, P<0.001). Median values of nocturnal scrotal temperatures did not significantly differ between 11 volunteers with normozoospermia and 22 men with oligozoospermia. Furthermore, continued scrotal temperature profiling during the following day only showed significantly higher values among men with oligozoospermia than among volunteers for the left scrotal side (+0.70 degrees C, P<0.05), but not for the right scrotal side (+0.39 degrees C, P>0.05). This difference could not be attributed to higher scrotal temperature values during periods with physical inactivity (median in both groups above 36 degrees C) but the duration of physical inactivity in men with oligozoospermia was 50% longer than in volunteers. Thus, in the setting of the present study it was not possible to demonstrate a close correlation between scrotal temperature and semen quality.