Frequent flyers, skiing, and hiking: high altitude’s links to fertility

The management consultant from a major Chicago-area printing company stepped forward to address a convention of book sellers, artisans, and production staffers at a recent convention held in the high Colorado ski town of Vail (elevation 8,022’ above sea level).

Though adjusting to altitude typically takes 24 to 48 hours for sea-level dwellers -- he’d been in the mountains for less than an hour – the consultant valiantly delivered his pitch for all of 60 seconds before succumbing to the effects of altitude sickness.

A host of research studies indicate that the effects of high altitude, where oxygen is scarcer and dehydration processes operate faster, could extend to male fertility. Both legend and science seem to agree on this point.

This intersection of lore and fact served as a jumping off point for one Pendleton Thomas, who penned a 1950 editorial entitled “Altitude and Fertility”.

Thomas noted at the outset that “aircraft personnel seem to form a disproportionately large percentage of infertile men” (these days, that should include frequent flyers, whether civilian or airline personnel).

Thomas quickly moved on to note that a colleague, in discussing altitude sickness, referred to a 1693 observation that Spanish conquistadors living at 14,000 feet in Peru didn’t father children until 58 years after their mountain city was founded.

About 150 years earlier, Thomas continued, Peru’s capital had been moved to a lower elevation because fowl, pigs, and horses had not experienced success in reproducing while living in the more rarified atmosphere. Thomas concluded that contemporary studies on animals had safely determined links between altitude and fertility; all that was needed was clinical trials on humans.

More contemporary research appears to have confirmed some of what Thomas theorized about.

For example, a 2003 study published in the journal Andrologia took a look at the exposure of high altitude on spermatogenesis, or the production of male sperm, in male rats.

The male rats were exposed to an altitude of 13,910 ft. (4340 m) in Cerro de Pasco, Peru, for periods of 3, 7, 14, 21, 28, 35 and 42 days. Sperm was studied at various day-intervals, with increasingly pronounced reductions in spermatogenesis as the days of exposure to high altitude continued to grow higher. The study authors concluded that “high altitude exposure affects spermatogenesis”.

Now onto a couple of the kinds of studies called for by Thomas on humans.

A 2016 study published in Andrologia examined sperm forward motility, or swimming ability, in male humans who had been exposed to short-term hypoxia, a deficiency of oxygen in the blood. In this case, the subjects were participants on a journey to explore Mt. Kilamanjaro over a five-day period, living and exercising at altitudes ranging from 2953 ft. (900 m) to 19,340 ft (5,895 m).

The study authors concluded, “The sperm forward motility at sea level after the expedition showed a significant reduction”.

For a quick comparison, the top elevation in Vail comes in at just under 12,000 ft., or roughly the middle of the range used in the Kilamanjaro study. Skiers and consultants alike there would stand to suffer effects to sperm motility even when visiting the area for just a few days after returning to sea level.

A 2015 study published in the journal High Altitude Medicine & Biology studied exposure to hypoxia at 17,651 ft. (5380 m) on young male adult humans over a period of one year. 52 male soldiers were enrolled in the cohort study as they underwent their service at altitude. Semen and blood samples were collected from the soldiers at intervals of one month before exposure, at six and twelve months of exposure, and six months after exposure.

Compared with readings taken one month before exposure, total sperm count, sperm density, motility, and survival rate “were significantly decreased”, the study authors noted, concluding, “[H}ypoxia at high altitude causes adverse effects on semen quality and reproductive hormones”. The study authors also noted that these effects were possible to reverse once the subjects had returned to living at sea level.

Yet another study on male military personnel, this one a 2016 study involving Chinese soldiers, found the following: “[H]igh altitude (> 3650 m [11,975 ft.]) has marked impact on semen quality.”

Given the inclination of people to engage in more frequent travel in formerly less accessible locales such as mountain villages and resorts -- particularly younger people wishing to do so before starting a family -- it’s clear that men need to take into account the potential harmful effects of high altitude on their assets and proactively store them prior to travel and exposure to oxygen-deprived places.