Comparison of sperm counts in two groups of men presenting for infertility investigations 20 years apart.

To compare sperm counts for two groups of men who had presented for infertility investigations approximately 20 years apart. The study compared results for 309 men tested between 1977 and 1981 with those of 559 men tested between 1997 and 1998 using identical methodology. In order to approximate the normal population, only those men with counts above 5 million/mL were included in the final analysis. Bias, due to repeated testing after an initial abnormal result, was minimized by including only the patient's first test results. In addition, to allow for time-dependent changes in the requirements for semen samples, results were included only if a complete sample was produced by masturbation after 3-5 days abstinence. There was a small, but statistically significant drop in ejaculate volume (3.9-3.6 mL,  = 0.015) and a significant increase in the patient's mean age (32.18 vs 35.08,  < 0.001). Both groups had median abstinence of 3 days and no difference in sperm counts with a mean (median) count for the early group of 87.9 (75) versus 92.0 (76) for the recent group ( > 0.80). The significant drop in ejaculate volume was not reflected in a difference ( = 0.45) in total sperm numbers in the ejaculate with 320.7 (255) versus 313.1 (234). This study found no evidence of a decrease in sperm counts or total sperm output in men (excluding those with severe oligospermia) presenting for infertility investigations in Melbourne, Australia, over the last two decades of the twentieth century. (Reprod Med Biol 2004; : 211-216).