What Lowers Sperm Count? Stay Cool. Hot Tubs, Jacuzzis, Laptops May Impact Male Fertility

What Lowers Sperm Count? Stay Cool. Hot Tubs, Jacuzzis, Laptops May Impact Male Fertility

Key Takeaways From This Article:

    • Heat exposure to the testicles is known to impact sperm production. Sperm is very sensitive to temperature changes and is produced at temperatures lower than body temperature.
    • Men’s choices can impact sperm count, especially when those choices expose the scrotum to excessive heat.
    • Men who are trying to have a baby should avoid hot tubs, Jacuzzis, hot baths, saunas, and the use of hot laptops on the lap. Men who have quit these activities can sometimes see improvement in sperm counts in as little as three to six months, but the long-term effects of repeated heat exposure is unclear and the long-term impact on male fertility has been noted for long-term and repeated heat exposure.  For example, research indicates that regular laptop users who use their laptops on their laps could be putting their long-term fertility at risk.
    • Tight-fitting clothing has also been linked to lower sperm count, due to the heat generated when wearing these clothes. Wearing loose-fitting clothing, or cotton and wool clothing can potentially help.
    • Researchers believe that the tight-fitting clothing cyclists wear could be a culprit in low sperm counts.


Human testicles are positioned on the body where they are (that is, anatomically separate from the body) in order to keep sperm at optimal temperature. Sperm, it turns out, are very sensitive to changes in temperature. According to Scientific American, the average man’s scrotal temperature is 2.5 to 3 degrees Celsius lower than body temperature, with sperm production being the “most effective at 34 degrees Celsius.” Basically, this means that sperm work best and are best produced at temperatures lower than body temperature.

Why is this the case?

One theory holds that when sperm reach body temperature, they become more active. However, sperm in this activated state only survive anywhere from 50 minutes to four hours—about as long as it takes a sperm to reach the egg after ejaculation.

Under normal circumstances, the testicles can shift toward the body and away from the body to adjust to small changes in temperature. But sources of more extreme heat stress can interfere with these bodily processes. Exposure to hot tubs, Jacuzzis, saunas, hot baths, and even hot showers can impact scrotal temperature. The clothes you wear can impact your body’s ability to maintain low scrotal temperatures. Excess fat around the scrotum can also cause problems. Even using a hot laptop on your lap can put men at risk of potentially long-term fertility issues.

What does this all mean for men who are trying to conceive? It means that the choices you make (particularly choices that could increase the temperature of your testicles) could potentially have an impact on your fertility.

Let’s take a closer look at the research.

Hot Tubs, Jacuzzis, Hot Baths, Saunas and Lowered Sperm Counts

Hyperthermia, or heat exposure to the testicles has been known to impair sperm production. Heat can decrease sperm concentrations, impair sperm motility, and result in the production of abnormal sperm. In many mammals (humans included) the testicles need to be cooler than body temperature (anywhere between 2 to 8 degrees Celsius cooler than body temperature) to properly produce sperm. This is why the testicles are structurally separate from the core body. According to the scientific journal, Human Reproduction, even a relatively small increase in temperature (as little as 1 to 1.5 degrees Celsius) can decrease sperm production and result in the production of deformed sperm.

Time in the hot tub, Jacuzzi, and in hot baths can reduce male fertility by reducing sperm counts. Research performed found that, for some men, reduction of time in the hot tub, Jacuzzi, or hot bath could result in increased sperm counts. It has long been suspected that exposure of the testicles to heat could reduce sperm counts, but this study is one of the first to quantify the impact of heat exposure to sperm counts. 45% of patients who stopped spending time in the hot tub, Jacuzzi, or hot bath saw a sperm count increase of 491%. The study identified and studied heat exposure risk in infertile men who spent more than 30 minutes each week in a hot tub, Jacuzzi, or hot bath. The average time the men spent soaking in hot tubs, Jacuzzis, or hot baths was 149 minutes each week.

Saunas can also have a similar effect on sperm count. A recent study published in the journal, Human Reproduction found that men who had two sauna sessions per week had lowered sperm counts and reduced sperm quality.

What about taking a long hot shower? Harvard Health Publishing lists hot showers among the potential activities that can elevate scrotal temperature and impact male fertility. So, if you’re trying to get pregnant and have been experiencing infertility, a switch to cool showers could potentially increase sperm count.

Let’s explore this further below.


Can Hot Laptops Really Reduce Sperm Count?

The same principle that holds true for hot tubs and saunas also holds true for hot laptops. Exposure of the scrotum to high temperatures (regardless of the source) can reduce sperm count and can lead to the production of abnormal sperm. Laptops can reach high temperatures, which could heat up the scrotum when the laptop is used on a person’s lap.

A study published in the scientific journal, Human Reproduction found that laptop use (on the lap) increased mean scrotal temperature by as much as 2.6 and 2.8 degrees Celsius. Studies have shown that an increase of scrotal temperature by 1 to 2.9 degrees Celsius “was consistently associated” with negative effects on sperm production and male fertility. While the research indicates that short-term exposure of the scrotum to heat (like short term exposure to heat in a Jacuzzi or hot tub) can be reversed, it isn’t clear to researchers whether the long-term exposure to this kind of sustained heat can produce irreversible effects on sperm count. One study found that when the scrotum was exposed to high heat consistently for five to seven years, the men studied had low sperm count, poor sperm motility, and abnormal sperm. And men who had been exposed to high heat for 12 to 15 years had a condition known as azoospermia, which is the absence of viable sperm.

Because younger men might be more likely to use laptops over longer periods of time, this research is particularly important to note. Long-term use of the laptop computer on the lap could potentially have long-term and potentially irreversible effects on male sperm count. When it comes to male fertility, using a laptop on a desk is your safest option.

Tight Fitting Clothing and Low Sperm Count

Can your clothing choices impact your sperm count? Tight-fitting clothing has been associated with raising the scrotal temperature in men. In fact, it is important to note that it isn’t entirely clear whether bike riding causes low sperm count or whether the culprit is the tight-fitting clothing the bicyclists wear. In a fascinating essay titled:   Clothes that can press the scrotum closer to the body can impact sperm count. Harvard Health Publishing lists some of the worst clothing offenders. They include:

  • Tight Jeans
  • Bicycle Shorts
  • Leather Pants
  • Clothes made of nylon or artificial fibers

When it comes to clothing choices, loose fitting clothes made of cotton or wool (clothes that can breathe) are your best bet.

Can Fat Impact the Temperature of the Testicles? 

Obesity can increase the temperatures of the testicles. When the scrotal temperature of obese men was monitored for 24 hours by researchers writing for Human Reproduction, obese men were found to have elevated scrotal temperatures associated with reduced sperm counts and poorer functioning sperm. Increased mass around the torso and legs can lead to “testicular heat stress,” which can impact fertility and sperm production, according to researchers studying the causes of obesity-related male infertility in the Expert Review of Endocrinology & Metabolism. And finally, researchers writing in the journal Reproduction also noted that fat accumulation around the scrotum can harm sperm production. Of course, heat isn’t the only factor that impacts fertility in obese men. Fat tissue can lead to hormone imbalances, low testosterone, inflammation in the testicles, and increased estrogen levels, which can also impact fertility. So, heat is just one of many factors affecting fertility in obese men.

Making Healthy Reproductive Choices for Men

If you plan to have a baby or have been having trouble conceiving, your lifestyle choices could have an impact on your ability to conceive, your sperm counts, and your overall health. Ultimately, if you have concerns about your sperm count or fertility, speaking to your doctor is the best choice. Small changes can make a big difference in your fertility. Daily Wellness, the makers of a daily wellness supplement for men, also offers a range of resources that can help you if you are trying to get pregnant, including FertilityBlend.

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