et al. examined young men from the general Danish population
that participated in compulsory medical examination related to military
service in two Danish cities (Copenhagen and Aalborg) in two periods
during 1996 and 1998. 708 participants contributed semen samples.
Concerns about possible selection bias in the first period led to
a less demanding protocol in the second. Subsequent analysis indicates
the initial concern was not warranted.
low sperm concentrations were found in this population of 18-20
year old men: the median sperm concentration of 41 million/ml was
significantly lower than the values found in previous national and
graph to the right is a frequency histogram illustrating the
percentage of men contributing samples with sperm concentrations
within a particular range of values.
Andersen et al. 2000.
is difficult to explain the low values of sperm count in young Danish
men. A short period of abstinence may contribute to a low sperm
count, but even when excluding those with a period of abstinence
below 48 h, more than 40% of the men had a sperm concentration below
significant correlation was also found between reproductive hormones,
sperm count and testicular volume, indicating that low sperm counts
were due to intrinsic biological factors rather than a short period
et al. note that Denmark has been shown to have high rates
of male reproductive abnormalities, including cryptorchidism and
sperm count is low enough to raise concerns about fertility.
According to WHO guidelines, a sperm concentration below 20
million/ml is abnormal.
et al. note that this guideline is arbitrary, and point to
a study (right) relating semen quality to fecundity suggesting
impairments in fecundity can be observed beginning at 40 million
sperm per ml.
et al. 1998
graph plots the likelihood of pregnancy within a given menstrual
cycle as a function of sperm concentration of the husband. The
dotted lines are 95% confidence interavals.