Data in previous research has been misinterpreted and repeated
The shared view that the quality of human sperm has been declining is erroneous, based on outdated research methods and misinterpretation of previous research results, Czech embryologist Pavel Trávník says.
Trávník, an expert in fertility defects who works in Repromeda, a Brno-based center of reproduction medicine and genetics, estimates that 92 in 100 men are fertile in advanced countries, he told the paper.
Also based on his research, Trávník dismissed the theory on a declining amount of spermatozoids.
“Evidently, a trend of decline has never been proved,” says Trávník who has published his conclusions in some articles.
He says it was probably a study by Danish scientist Elisabeth Carlsen and her colleagues from 1992 that caused an uproar among experts and stirred panic over an alleged decline in the number of spermatozoids.
“It triggered off a wave of fear for the fate of mankind and the spending of huge sums on studies enquiring into the causes of this phenomenon,” Trávník said.
“When reading the [Carlsen] study attentively, we find out that the authors assessed data wrongly, without taking into account the too small size of the samples under examination,” Trávník pointed out.
Carlsen and her team compared their analyses with those made in the 1930s and 1940s when the analysis methods and laboratory equipment were insufficient, Trávník said.
The next results can hardly be comparable with modern ones, he said.
He points to another international study from 1995, according to which the average concentration of spermatozoids was 73 million per one millimeter in 1969-70 and it remained unchanged in 2010, through it would have dropped to 44 million per milliliter, if Carlsen’s theory had been correct.
A few years ago, Trávník himself analyzed about 6000 samples, and he found out that no decline in the parameters had occurred in the previous decade.