Sperm count more than halved in Western men

Sperm approaching egg

Tim Newman  
In the largest study of its
kind, researchers find that sperm count in Western countries has more than
halved in recent decades. Outside of these countries, however, the decline is
not significant.
The question of whether or not
sperm count is declining has been hotly debated for many years within the
scientific community. However, no firm conclusion has been reached.
Of course, a reduced sperm
count has important implications for reproduction, but this is not the only
reason for alarm; low sperm count has been shown to increase the risk of
all-cause mortality and morbidity.
For instance, a study
published in 2014 concluded that “those with abnormal semen parameters
have a higher risk of death, suggesting a possible common etiology between
infertility and mortality.”
Also, reduced sperm count is
associated with deformation of the penis (hypospadias), a testicle that has not
moved into the scrotum (cryptorchidism), and testicular cancer.
Another general concern is
that sperm count and other measures of semen quality might be a sign that we
are living in a toxic environment. The more we understand about this, the better
we can approach making informed changes to the chemicals that we use every day.

Gathering data on sperm count

With these factors in mind, a
group of researchers recently set out to conduct a large-scale systematic
review and meta-analysis of sperm count trends.
For the study, a group from
the Hebrew University-Hadassah Braun School of Public Health and Community
Medicine in Israel joined forces with the Icahn School of Medicine at Mount
Sinai in New York City, NY. Their results are published this week in the
journal Human Reproduction Update.
They screened 7,500 studies
and completed a meta-regression analysis on 185 studies carried out from 1973
to 2011. The results were clear and surprising.
Men from Europe, North
America, Australia, and New Zealand had a 52.4 percent decline in sperm
concentration and a 59.3 percent decline in total sperm count.
In contrast, no significant
decline was found in men from Asia, South America, and Africa – although there
were fewer studies to analyze in these regions. Worryingly, the rate of decline
in Western men did not appear to be slowing; “the slope was steep.”
Even when the analysis was limited to studies from 1996 to 2011, the trend was
still significant.
The implications of reduced
sperm count

Since 1992, the question of
whether sperm count is steadily dropping has been widely debated. Although
earlier studies have addressed this problem with varying results, the current
research has a broader scope.
To ensure the analysis was as
accurate as possible, the researchers controlled for a thorough array of
potential factors. These included abstinence time, method of semen collection,
how the sperm were counted, age of participant, how the study population was
selected, and how many samples were given per man.
“Given the importance of
sperm counts for male fertility and human health, this study is an urgent
wake-up call for researchers and health authorities around the world to
investigate the causes of the sharp ongoing drop in sperm count, with the goal
of prevention.”
-Lead author Dr. Hagai Levine

The authors believe that,
because the decline is only seen in Western countries, “chemicals in
commerce” may be playing a role in the downward trend.
Although the current study did
not address the direct cause, decline in semen quality has been previously
associated with pesticides, heat, lifestyle factors, diet, smoking, stress, and
body mass index (BMI). The researchers ask whether the declining sperm count
may be the proverbial “canary in the coal mine.”
Because the study analysis was
so detailed, and the dataset so varied – namely, it was spread evenly across 39
years and 50 countries – the findings are particularly robust, and they are,
therefore, particularly worrying.
With connections already drawn
between reduced sperm count and overall mortality, the authors write,
“Research on causes and implications of this decline is urgently
Kayode Ojo
Kayode Emmanuel Ojo is the Co-Founder and Managing Director at SHEFFA Limited. He is presently studying Computer Science at the National Open University, Victoria Island, Lagos.