Differences in the quality of semen in outdoor workers during summer and winter

Article Abstract:

In nonequatorial areas of the globe with warm climates, fewer babies are born in the spring. This could result from lower sperm quality nine months earlier, possibly as a result of exposure of the scrotum (the sac holding the testicles) to greater summer heat. To evaluate sperm quality, researchers collected sperm from 131 outdoor workers (average age, 32) during the summer (August) and winter (February), to allow comparison of sperm characteristics for the same men sampled at two different times. The study was performed in San Antonio, Texas, where the average summer temperature is 35.9 degrees Centigrade (96.6 degrees Fahrenheit), and the average winter temperature, 17.7 degrees (63.9 degrees F.). Data regarding the men's drug use, health, type of work performed, marital history, and related factors were obtained. Videotape recordings of semen specimens were analyzed to determine the percentage of motile (moving) sperm, sperm velocity, the number of beats per unit time of the flagella (tails of the sperm), and other characteristics related to sperm quality. Results showed that this group of men were more likely than the average American male to smoke and to consume two or more alcoholic drinks per day. About one third of the men performed construction work, 17 percent did landscaping, and eight percent drove a motor vehicle. In summer, sperm concentration, sperm count per ejaculate, and the concentration of motile sperm were lower than in winter (by 29, 23, and 26 percent, respectively). Other characteristics, such as volume of seminal fluid, percentage of motile sperm, characteristics of sperm movement, and length of sexual abstinence, did not differ between seasons. No correlation was observed between the number of hours a man worked outside, and seasonal differences in sperm characteristics. The results parallel those of other studies, which are discussed. Several factors, including the lower summer sperm counts among men in cooler climates, and the peak in birth rates in the spring in Europe (in spite of decreased sperm counts in the summer), imply that heat is not a complete explanation for birth rate effects. (Consumer Summary produced by Reliance Medical Information, Inc.)

Measurement, Semen

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Fewer sperm in the summer: it's not the heat, it's...

Article Abstract:

Spermatogenesis (the manufacture of sperm) remains a puzzle for investigators. Testosterone (male sex hormone), present in the testes at a level 100 times that of the general circulation, determines spermatogenesis, but the influence of follicle stimulating hormone and luteinizing hormone on this process are not understood. Some causes of male infertility are known, such as Klinefelter's syndrome, androgen (male sex hormone) resistance, and the effects of X-ray. Cryptorchidism (undescended testicles) and varicocele (enlargement of the veins of the spermatic cord, the structure to which the testicle is attached) are thought to be associated with infertility because they increase testicular temperature. Is this, in fact, likely? The temperature in the scrotum is normally two to three degrees Centigrade lower than the rectal temperature, and when it is raised (as in fever), sperm counts decrease. Undescended testicles are exposed to higher temperatures inside the abdomen, and experimental production of this condition led to a reduction of 90 percent in sperm number. However, other factors are also significant, since men with corrected cryptorchidism often have lower sperm counts. A role for heat in infertile men who have a varicocele is not easily defended, in contrast. Men with higher intrascrotal temperatures, with or without a varicocele, produce fewer sperm. Research suggests that a testicular abnormality leads to increased temperature, rather than the reverse. Surgical correction of varicoceles does not lead to improved fertility. A study in the July 5, 1990, issue of The New England Journal of Medicine found seasonal variability in sperm production. Sperm counts were lower in summer than winter among men who worked outdoors in a warm climate (Texas); however, the magnitude of the seasonal variation was not correlated with the amount of time the subjects spent outdoors in the heat. Again, heat does not appear to be the mediating factor. The complexity of spermatogenesis can be studied in well-controlled clinical studies, with the ultimate goal of allowing men to select the level of fertility they desire. (Consumer Summary produced by Reliance Medical Information, Inc.)

editorial

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Hypogonadism in elderly men--what to do until the evidence comes

Article Abstract:

Doctors should only give testosterone replacement therapy to men who have blood testosterone levels below 200 nanograms per deciliter. These men should also be screened for any potential diseases that may be exacerbated by testosterone treatment. And they should have regular check-ups to prevent the development of such diseases.

Care and treatment, Testosterone, Hypogonadism

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