Calculation of the incidence of infertility in human populations from sperm measures using the two-distribution model.

A model, designated the two-distribution model, has been developed to estimate the incidence of human infertility based on alterations in sperm measures. Such alterations could be based on those obtained in populations exposed to a potential reproductive toxin or extrapolated from animal studies. The model requires distributions of sperm measures as input data; studies in which only averages and measures of variation are presented would not provide data bases useful for these calculations. To make the model more applicable and reliable, assumptions within the model need to be tested, additional data on distributions of sperm measures in defined human populations are needed, and possible extensions of the model need to be considered.