Decrease in Sperm Parameters in the 21st Century: Obesity, Lifestyle, or Environmental Factors? An Updated Narrative Review

Abstract

Semen quality represents a compelling factor for fertility, and delineating the normal values has proven difficult. In the last four decades, several authors have reported a noticeable decline in sperm parameters. Also, studies investigating ‘time to pregnancy’ have shown that fecundity begins to be reduced when sperm numbers decrease below 30 million, even though according to the 6th edition of the WHO manual, the normal value is currently 16 million/mL or 39 million per ejaculate. There exists sufficient data to suggest a decline in sperm counts over time, even though the clear reason for this adverse trend is not well established, but some associations have been hypothesised, such as maternal smoking during pregnancy. Additional potential factors have yet to be fully illustrated but involve poor diet, increased obesity, and exposure to environmental toxins. Moreover, the change in environmental conditions and more common exposure to endocrine-disrupting chemicals (EDCs), such as pesticides and herbicides, as well as bisphenol A, phthalates, polychlorinated biphenyls, and heavy metals, starting from prenatal life and continuing into adulthood, may exhibit probable features explaining the reduction in sperm parameters. Therefore, the main goal of this narrative review is to furnish an overview of the possible effects of exposure to EDCs on testicular function and spermatogenesis and, also, to summarise the evidence regarding a decrease in sperm quality and examine its potential consequences.

Experimental Model Exposed to Bisphenol and Submitted to a High-Fat Diet and Related Morphologic Testicular Parameters Alterations Analysis

“…Exposure to BPA was associated with decreased sperm concentrations and impaired sperm parameters, as well as a raised percentage of immature sperm and reduced testosterone levels ( 24 ). In a nice previous study the authors shows that exposure of male rats to BPA and is analogs BPB, BPF, and BPS resulted in decreased sperm production, testosterone secretion, and histological changes in the reproductive tissues ( 25 ).…”

Environmental Factors as the Main Hormonal Disruptors of Male Fertility

“…Many scientific reports confirm a systematic decline in the parameters of male semen over the last decades [3,4]. This phenomenon is observed in all parts of the world, and its occurrence is associated, among others, with the adverse effect of some environmental factors [5]. The environmental factors for which the unfavorable effect on male fertility has been proven include water, air, and soil pollution, as well as electromagnetic fields and ionizing radiation [6].…”

Editorial for the Special Issue “Environmental Exposure and Reproductive Health”

“…In recent decades, the decline in human fertility has emerged as a significant public health concern, garnering global attention. There are numerous factors contributing to the decline in fertility, with environmental pollution being notable [ 1 , 2 ]. Toppari et al proposed the “endocrine disrupting hypothesis”, suggesting that exposure to endocrine-disrupting chemicals (EDCs) during fetal or infant development may affect the development of reproductive organs and subsequently have adverse effects on reproductive health in adulthood [ 3 ].…”