Sperm counts in the Western world have declined nearly 60 percent since the 1970s

What’s causing the dramatic decline remains unclear, but chemical exposure is a possible culprit.

In a comprehensive study published in Human Reproduction Update, researchers analyzed data from studies spanning 1973 to 2011. Over this time period, they found a drastic drop in both sperm concentration and sperm count among men in North America, Europe, Australia, and New Zealand. No decline this significant was documented in other parts of the world, where less data is available. The study also shows that the rate of decline in the West has not slowed in recent years. The authors say their findings should spur “massive” efforts to identify and address the cause of this decline, which is still unknown. We spoke with lead researcher Hagai Levine, an epidemiologist and public health physician at the Hebrew University-Hadassah, about these findings.

ResearchGate: How have Western men’s sperm counts changed over the years?

Hagai Levine: We see a 52.4 percent decline in sperm concentration and a 59.3 percent decline in total sperm counts from 1973 to 2011 for men not selected based on their fertility status.

RG: How does this compare to other parts of the world?

Levine: It is a significantly steeper decline than in non-Western countries. However, there is scarce data for non-Western, and we can't conclude the trend there.

Hebrew University

RG: What implications does this have for fertility and population growth?

Levine: First, these data demonstrate that the proportion of men with sperm counts below the threshold for subfertility or infertility is increasing. Clear effects on population growth will only be seen when a significant proportion of the population has very low fertility. Moreover, given the findings from recent studies that reduced sperm count is related to increased morbidity and mortality, the ongoing decline points to serious risks to male fertility and health.

RG: Do you have any ideas about what’s causing this drop?

Levine: We don't know for sure why this is happening, but our findings should drive massive scientific effort to identify the causes, and modes of prevention. From previous studies—including some of ours—we know that exposure to endocrine disruptors in utero (e.g. from maternal smoking or stress) can harm male reproductive system development and fertility potential. Later in life, exposure to chemicals such as pesticides or smoking, as well as obesity, can harm sperm counts.

One possible explanation is that men residing in Western countries over the last decades were exposed to new man-made chemicals during their life course, and there is more and more evidence that these chemicals hurt their reproductive function. We also need local knowledge regarding exposure and effects. For example, I am studying pesticides exposure and male fertility in Israel, as pesticides exposure is common.

RG: What trends do you predict for the future?

Levine: Prediction is difficult, especially about the future. We will leave the speculation for others. Instead, we should focus on the immediate clear and present danger and take care of the issue now, as there is clearly something wrong in terms of health and fertility for a large proportion of the male population in Western countries. Our actions will determine if and when declining male fertility will threaten the existence of our species. We need multidisciplinary, preferably international teams to study such questions.

Featured image courtesy of Zappys.