Evidence that chronic hypoxia causes reversible impairment on male fertility

To evaluate the effect of chronic hypoxia on human spermatogenic parameters and their recovery time.

Seminological parameters of six male healthy mountain trekkers were evaluated in normoxia at sea level. After 26 days exposure to altitude (ranging from 2 000 m to 5 600 m, Karakorum Expedition) the same parameters were again evaluated after returning to sea level. These parameters were once again evaluated after 1 month and then again after 6 months.

Sperm count was found to be lower immediately after returning to sea level (P = 0.0004) and again after a month (P = 0.0008). Normal levels were reached after 6 months. Spermatic motility (%) shows no reduction immediately after returning to sea level (P = 0.0583), whereas after 1 month this reduction was significant (P = 0.0066). After 6 months there was a recovery to pre-hypoxic exposure values. Abnormal or immature spermatozoa (%) increased immediately after returning to sea level (P = 0.0067) and then again after 1 month (P = 0.0004). After 6 months there was a complete recovery to initial values. The total number of motile sperm in the ejaculate was found to be lower immediately after returning to sea level (P = 0.0024) and then again after 1 month (P = 0.0021). After 6 months there was a recovery to pre-hypoxic exposure values.

Chronic hypoxia induces a state of oligospermia and the normalization of such seminological parameters at the restoration of previous normoxic conditions after 6 months indicate the influence of oxygen supply in physiological mechanisms of spermatogenesis and male fertility.