 |
| Courtesy: bbc.com |
A huge
systematic review and meta-analysis has found a continuing decline in sperm
count by an average 1.4% per year among western men between the year 1973 to
2011. The results made headlines and were published 25 July 2017 in Journal of
Human Reproduction Updates. The decline of 50% in four decades was so
significant that the study results made headlines.
Hagai
Levine, the lead researcher and faculty member of the Braun School of Public
Health and Community Medicine at Hebrew University-Hadassah in Jerusalem says, “This
is a wake-up call to study the causes of this decline, aiming to prevent
further deterioration.”
Whether
sperm counts have declined or not is debated since very long and the controversy
remains fluid because of limited number of studies addressing this issue.
Besides
being the first step in diagnosing male factor infertility, sperm count is of
considerable public health importance. Reduced sperm count is a predictor of high
all-cause morbidity and mortality, besides incurring a high financial burden on
the society. It is also linked to a range of male reproductive problems like cryptorchidism,
hypospadias, testicular cancer, low testosterone levels and increased utilization
of Assisted Reproductive Techniques. There
has been a 65% increase in IVF treatments since 2003 according to a survey results
of young US adults by the Reproductive Medicine Associates of New Jersey.
Low Sperm
Counts is also a mirror of environmental influences on our endocrine system because
of modern life style. They reflect the influence of endocrine disrupting
chemicals, pesticides, changes in environmental temperature and life style
factors like smoking, diet, stress and BMI.
The researchers
identified 7518 studies meeting the study protocols, from which 185 studies
amounting to nearly 43000 subjects who provided samples between 1973–2011 were
selected for final analysis.
Data was
available across 6 continents and nearly 50 countries.
For final
analyses, the countries were grouped into ‘Western’ including studies from
North America, Europe, Australia and New Zealand and ‘Other’/ ‘Non-Western’ including studies from all other
countries like South America, Asia and Africa.
Meta- regression analyses showed that mean sperm
concentration (SC) was 81 million/ml, the mean total sperm count (TSC) was 260
million and the mean year of data sample collection was 1995.
Sperm concentrations declined by 50% and total sperm count by
nearly 60% over the years among men unselected by fertility primarily from
North America, Europe, Australia and New Zealand. The study saw no significant declines
for studies from South America, Asia and Africa, possibly because of limited
number of studies available from these geographic areas.
The statistic reflects the fact that an increasing number of
men will have sperm counts below any given threshold for sub-fertility or
infertility. Quite a large percentage of Western men have concentration
below 40 million/ml, decreasing the probability of natural conception.
This decline remained unchanged after controlling for various
confounders like age, abstinence time, method of semen collection, method of
counting sperm, selection of population and study exclusion criteria, number of
samples per man and completeness of data.
While it is not possible to rule out the falling trend in
semen parameters in non-western countries it is certain that the decline is not
as steep as observed for their western counterparts.
The continuing decline of sperm count in western males is
regarded as ‘canary in the coalmine’ for male health across the life span and
calls for more studies and research urgently to put a stop to this damning
trend.
