Sperm concentration: evolution over the past four decades

To shed light on the controversial question of whether there is a falling trend in sperm count, the authors reviewed 185 studies providing sperm count data in sperm samples collected between 1973 and 2011(star). The meta-regression analysis indicated that in these four decades sperm concentration decreased by over 50% in men from western countries. The decline of 1.4% per year showed no signs of slowing in the most recent period.