Factors such as changes in sperm counting methods, obesity, and smoking were considered as potential confounders for the observed decline in sperm count.

“you know maybe the method of counting sperm had changed so that later methods counted fewer sperm in the same sample that's certainly possible right um but it turned out that wasn't the case cuz they actually had all used the same method um and maybe the men had changed so maybe there's a you can't get a sperm count at random you have to get somebody to volunteer right so who were these men were they very different you know in the early part of the study and the late part of the study in a way that maybe in the late part of the study there were men with lower sperm gut and they were more concerned you know maybe they were more obese that's pretty plausible obesity is related to se sperm Camp fertility um and maybe they smoked more and maybe and so on and so forth right”