Environmental interference and declining male fertility.

Abstract

Declining human male 'fertility' has been equated with a temporal decline in sperm counts, with reports collectively spanning the period between 1934 and 2018. Although sperm quality is impacted by adult male lifestyle choices, e.g. diet, stress and exposure to heat, environmental factors are thought to be central to this alarming observation. Since the decline in sperm counts reflects the outputs of meta-analytical studies, and thus the combination of data from different laboratories, statistical models have had to control for potential confounders, including differences in laboratory methodologies, changes in quality assurance standards, age, fertility group and exclusion criteria indicators. Sperm analyses arising from a population of stud dogs, where all analyses were carried out in a single laboratory, demonstrated a 30% decline in sperm motility over 26years. Since these dogs resided in normal homes and were therefore exposed to the same household environment as human cohabitees, it has been postulated that the temporal decline in both dog and human sperm quality reflects environmental interference. This viewpoint article explores this contention and its implications for male 'fertility'.