![]() It likewise found a decrease in total sperm count after three weeks of use. A different study had participants wear insulated jockstraps for six to fourteen weeks. The results were intratesticular temperatures of 40–42 ˚C (104–108 ˚F) and infertility. One study exposed participants’ testes to microwave radiation for thirty minutes every three weeks. This turns out to be quite important because an increase in scrotal temperature of just a few degrees can inhibit spermatogenesis and cause infertility. The testes are covered by the cremaster muscle, which involuntarily contracts or relaxes to either draw the testes closer to the body for warmth or away from the body to cool. Human testicles are usually maintained at 35 ˚C (95 ˚F), about two degrees lower than body temperature, and have an impressive capacity for thermoregulation. Much of the research on how lifestyles can affect male fertility concerns various ways in which a person’s testicles could be warmed up. Smoking’s effects on sperm seem to cross generations too: “After adjustment for confounding factors, men exposed to smoking in utero had a reduction in sperm concentration of 20.1% … and a reduction in total sperm count of 24.5%.” All the more reason to encourage expecting mothers not to smoke. Smoking CigarettesĪ 1994 meta-analysis found that the sperm density of smokers is on average 13 percent to 17 percent lower than that of nonsmokers, although the researchers were not able to identify a dose-dependent relationship between the number of cigarettes smoked per day and sperm density. Much like marijuana, cocaine use, even only within the past five years, is associated with low sperm counts, low motility, and high concentrations of abnormal sperm cells. Nonetheless, we can look at overall trends in the scientific literature and draw some conclusions about what facets of your life are likely to influence your fertility.Īccording to a 2015 review, “It is clear that marijuana and its compounds can influence male fertility at multiple levels.” Specifically, marijuana can cause decreased sperm density and low motility. Unfortunately, studies of such size are expensive and complex and therefore rare. This means that while we can detect large changes in sperm quantity or quality, more subtle alterations in sperm characteristics are distinguishable only in large studies. Human males are really inefficient at producing sperm.Īs infertility researcher Richard Sharpe writes, “The poor average quality of human semen, combined with the naturally great variation in semen quality between individuals and from ejaculate to ejaculate in the same individual, means that cross-sectional studies in men face an uphill task when attempting to establish whether or not occupation, lifestyle or other environmental exposures are able to affect sperm production or quality.” Besides being another piece of trivia to add to my arsenal of hamster knowledge (Did you know that hamsters are omnivores, even though most pet hamsters are fed vegetarian diets?), this fact highlights a problem that makes researching lifestyle contributions to male fertility difficult. Until I started researching this article, that is. This article was first published in The Skeptical Inquirer.ĭid you know that the average cisgendered male human produces approximately the same number of morphologically normal sperm per day as a hamster, despite having testicles ten times the size? Yeah, me neither.
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