Scrotal and Testicular Heat Exposure

The process of spermatogenesis (creating and maturing sperm) is temperature-dependent and occurs optimally at temperatures slightly lower than that of the body: must range from 2 to 8°C below body temperature. Raised testicular temperature has a detrimental effect on spermatogenesis and the resultant spermatozoa. Thermoregulatory failure leading to heat stress can compromise sperm quality and increase the risk of infertility.

Lifestyle, behavioural, occupational and pathophysiological causes of testicular heat stress encompass modifiable factors that are a result of habit or practices that could be altered or avoided with conscious effort.

Higher temperatures lead to an increase of testicular metabolism that results in spermatic damage.

Oxidative stress is the main factor responsible for testicular damage caused by heat stress. Testicular heat stress induced oxidative stress that led to rescuable alterations after one spermatic cycle in ejaculated sperm and also after 30 days in epididymal sperm.

Clothing and Posture

Testicular temperature depends on scrotal position, which differs with postural changes. Scrotal temperature is at its lowest on an unclothed, upright body as the position.

Scrotal temperatures are lower when walking compared with sitting because scrotal movement during ambulation provides better air circulation and heat dispersion. A predominantly sedentary or seated position during long stretches of passive tasks such as working at the computer or commuting increases scrotal temperatures. Heat from the seated surface, as from a heated car seat or a heated floor, further adds to scrotal temperatures that are already elevated from being in a seated position.

Although the effect of tight underwear versus boxer shorts on sperm parameters is inconclusive, it would seem that tighter-fitting undergarments would leave less room for scrotal movement and air circulation hence contributing to higher genital temperatures.

Hot baths and sauna

The use of hot baths and sauna for relaxation and rejuvenation may make one feel better, but also has a negative effect on semen quality.

Full-body immersion in a warm bath, hot tub, heated Jacuzzi or whirlpool at temperatures over 36.9°C for 30 min or more a week for 3 months or more leads to wet hyperthermia, which could have a reversible negative effect on sperm motility.

Studies show that, after sauna exposure, scrotal temperatures reach up to body temperatures within 10 mins, and there is a significant but reversible negative effect on spermatogenesis.

In saunas with temperatures ranging from 80–90°C, and at different frequency and duration of exposure, the use of saunas could disrupt spermatogenesis and cause abnormal sperm count and motility.

Laptop use

Having a computer on the lap, close to the genital area, and sitting with one’s legs close together for long hours increases scrotal temperature, which may negatively affect sperm parameters.

Cycling

Among the different types of exercise, cycling is one that is reputed to impair male fertility.

Aspects of cycling that may influence scrotal temperatures include posture, duration and intensity of cycling, and the attire.

Particularly in professional cyclists, extended periods of cycling in form-fitting spandex outfits and being seated for long hours on a saddle seat is likely to cause elevated scrotal temperatures.

Radiant heat

Certain labour-intense jobs entail exposure to long periods of intense, radiant heat. Welders, for example, are exposed to strong levels of heat, toxic metals and fumes during welding. Studies involving these workers demonstrate reversible decline in semen quality.

Those working directly with sources of severe heat, such as bakers and ceramic oven operators, have a longer time to pregnancy, which suggests that occupational heat exposure has an effect on fertility. Men who work in close range to sources of intense heat, such as the rear end of a submarine (location of motor) seem to face infertility-related problems.

Professional or occupational drivers and individuals who have long daily commutes are more prone to having increased scrotal temperatures, poorer sperm quality and longer time to pregnancy. The negative effect of long hours of driving and seated commutes increases in severity with the number of years spent engaging in such activities.

Cryptorchidism

Failure of the testis to fully descend into the scrotal sac before birth or within the first few months of life could lead to subfertility and increased risk of testicular germ cell cancer. •An undescended testis is exposed to body temperatures and, although painless, it could lead to heat-induced changes in the spermatogenic process, which affects the germ cells, spermatozoa, testis and testicular hormones.

Varicocele

The temperature of a testis affected with varicocele is about 2.5°C higher than a normal testis and in an infertile individual, scrotal hyperthermia is most likely varicocele-related. •Higher scrotal temperatures in varicocele patients with infertility lead to sperm DNA fragmentation and apoptosis, as well as hormonal imbalance.