Are Western Countries in a Sperm Crisis?

According to a new study, men living in industrial countries produce only half of the sperm count compared to 40 years before. But the results are controversial like every other study about sperms before.

Men from western industrial countries produce only half the count of sperms as in the beginning of the Seventies in the 20th century. This result was reached by a working group around Hagai Levine of the Hebrew University in Jerusalem and the analysis has been published in the magazine "Human Reproduction Update" under the name Temporal trends in sperm count: a systematic review and meta-regression analysis. From around 7500 researches about this topic, the group choose 185 suitable studies to exclude eventual confounding factors. According to this data, the study comes to the result, that sperm concentration has decreased about 52 percent and sperm count almost 60 percent. According to the publication, the trend has stayed the same in the whole time frame, which would mean, that there are no signs indicating that the problem is ceasing. By contrast there seems to be no decrease in the rest of the world. However, the study doesn't tell us the reason which is responsible for the sperm decline. Therefore it is unclear if the low numbers actually indicate a decline in fertility.

(a) Mean sperm concentration by year of sample collection in 244 estimates collected in 1973–2011 and simple linear regression.
(b) Mean total sperm count by year of sample collection in 244 estimates collected in 1973–2011 and simple linear regression.

Reports about declining sperm count are frequent. The results go back into the early years of 1990, but were debatable from the beginning. The suspicion which persists is the question if selection bias is responsible for the lower numbers, f.e. because men with fertility problems are over represented in such studies or because unobtrusive reports are less commonly published. This mentioned effects should have been disabled by the new large-scale study.

(a) Meta-regression model for mean sperm concentration by fertility and geographic groups, adjusted for potential confounders.
(b) Meta-regression model for mean total sperm count by fertility and geographic groups, adjusted for potential confounders.

According to Stefan Schlatt from the University of Münster (Germany) this could be achieved:

"This study is the best recalculation that currently exists."

Methodically this attempt should be flawless in his opinion. Furthermore the study is showing, that the negative trend regarding sperm count is stable. The scientist adds for consideration, that such numbers do not necessarily indicate a decline in the fertility of men.

The andrologist Sabine Kliesch from the University Clinic of Münster floats the suggestion, that the measured trend could be an artifact of changes in the measuring method: Only since the beginning of the century mechanisms for quality control exist and also the equipment which is needed to collect the data has changed in the questionable period. Even if the numbers were correct, they are not necessarily representing an alarm signal.

"The shown changes are all within a highly normal range."

A restriction of fertility can not be expected according to this numbers.

Should the decline be real this would be a warning signal regarding health, also independent of restricted fertility. Diverse factors can reduce fertility, including life-style effects like: smoking, stress or overweight.

Environmental chemicals are on the list of suspects to be responsible for the decline in sperm count - but except smoking there is only evidence for the influences of all this factors.