A relationship between experimental elevation of testis temperature and poor semen quality has been known for over eighty years.
Experience shows that prolonged reduction of the temperature of the scrotal area by about 2 to 5 degrees C., may be effective in reversing male infertility and there are numerous published study data to support this theory, a selection of which are here;
Mulcahy JJ, J Urol 1984: 132:469-70
Abstract: Fifty men with reduced sperm motility were tested with scrotal cooling by ice packs applied to the scrotum at night and held in place with jockey shorts. Sperm density and motility were compared before and after treatment. At least a 2-fold increase in sperm density and comparable increases in sperm motility were seen in 65 per cent of the patients in this series. The percentage of successful treatment was the same whether or not a varicocele was present. These results further support the detrimental influence of heat on spermatogenesis
J. Reprod. Fert. (1988) 82, 563-566
Measurement of intrascrotal temperature in normal and subfertile men.
Summary: Scrotal temperatures were measured in 300 sub fertile men (mean sperm count 21.4 million/ml) and 30 control men (mean sperm count 118.7 million/ml). The sub fertile men had mean temperatures of 34.75 degrees C for the testes. The value for the testes of the control men was
33.4 degrees C.
The difference 1.35 degrees C was significant (P= 0.03). An intrascrotal temperature above 34.1 degrees C was found in 83% of the sub fertile men, regardless of clinical diagnosis. We suggest that small intrinsic temperature increases may interfere with the ability of the testis to accommodate to environmental temperature stresses and so lead to abnormal semen and sub fertility.
European Journal of Obstetrics & Gynecology & Reproductive Biology, 29 (1988) 137-141. Influence of occupation and living habits on semen quality in men (scrotal insulation and semen quality)
Abstract: 56 Infertile couples were split into two different groups and their semen quality examined. Patients in which there was no evidence or interference with normal testicular thermo regulation either during the day or the night were classified as ‘cool workers’ and ‘cool sleepers’ In the other Group, ‘warm workers’ and ‘warm sleepers’, there was evidence for scrotal insulation. The number of good moving spermatozoa per ejaculate as well as the number per ml was greater in ‘cool workers/sleepers’ than in ‘warm workers/sleepers’.
Human Reproduction vol. 15 no.6 pp.1355-1357, 2000
Increase in scrotal temperature in car drivers.
Scrotal temperature increases while driving a car. This study demonstrated that driving is associated with an increase in scrotal temperature.
Such an increase reaches a value of 1.7 to 2.2 degrees C when driving continuously for more than 2 hours. The question arises as to what the consequences of an increase in scrotal temperature on sperm characteristics and or fertility might be. Normal human testicular temperature is physiologically maintained within a range 32 -35 degrees C (Mieusset and Bujan, 1995). As in most mammals, such a normal testis temperature is a necessary condition for quantitatively and qualitatively normal spermatogenesis (Setchell and Mieusset, 1996). In human experimental studies in which a 1-2 degree increase in testis temperature was induced at least during waking hours and repeated daily, spermatogenesis was impaired: sperm count and percentages of motile and of normal form spermatozoa were depressed (Mieusset et al., 1985, 1987; Shafik, 1992; Mieusset and Bujan, 1994).
2005: Jung A; Schill W-B; Schuppe H-C
Improvement of semen quality by nocturnal scrotal cooling in oligozoospermic men with a history of testicular maldescent.
International journal of andrology 2005;28(2):93-8.
The aim of this study was to evaluate the influence of nocturnal scrotal cooling on semen quality in such patients presenting with oligozoospermia. Twenty infertile men with a history of testicular maldescent and oligozoospermia were included for nocturnal scrotal cooling over 12 weeks for every night. Semen analysis was performed at the beginning of the cooling period and at weeks 4, 8 and 12. Another 20 infertile patients with a history of testicular maldescent and oligozoospermia were followed without specific treatment and served as a retrospectively built control group. Scrotal cooling at night resulted in a scrotal temperature drop by 0.8 degrees C (median). A significant increase in sperm concentration and total sperm count was achieved by nocturnal cooling after 8 weeks and 12 weeks respectively. The improvement of sperm motility and sperm morphology was statistically insignificant. This study suggests nocturnal scrotal cooling as a therapeutic option.