Improvement of semen quality by nocturnal scrotal cooling and moderate behavioural change to reduce genital heat stress in men with oligoasthenoteratozoospermia.

Plain-language summary

This study looked at whether reducing genital heat could improve semen quality in men with a poor sperm count, poor movement and abnormal shape. It compared those men against men with normal semen, measured scrotal temperature around the clock, and then tested a device that blew a stream of air across the scrotum overnight. The men with poor semen results ran hotter than the comparison group at the same room temperature, and in 88% of cases the highest scrotal temperature of the day was recorded during rest or sleep rather than during activity. Twelve weeks of overnight cooling, together with a moderate reduction in everyday sources of genital heat, lowered scrotal temperature by about 1 degree Celsius (1.8 degrees Fahrenheit) and produced clear improvements in sperm concentration and total sperm output. Movement and shape improved too, but markedly less. The two changes were made together, so what the cooling did on its own cannot be separated out.

Key findings

• Men with a poor sperm count, poor movement and abnormal shape ran hotter scrotal temperatures than men with normal semen at the same room temperature.
• In 88% of cases the highest scrotal temperature of the day came during rest or sleep, and the lowest came during physical activity or frequent changes of position.
• Overnight cooling with an air stream lowered scrotal temperature by about 1 degree Celsius (1.8 degrees Fahrenheit).
• After 12 weeks, sperm concentration and total sperm output both improved clearly.
• Sperm movement and shape also improved, but markedly less than concentration did.
• The cooling was combined with a moderate reduction in everyday sources of genital heat, and there was no untreated group, so the effect of the cooling alone cannot be separated out.