Macleod Revisited: Sperm Count Distributions in 374 Fertile Men From 1971 to 1994

Emanuel, Eric R.; Goluboff, Erik T.; Fisch, Harry

doi:10.1016/s0090-4295(97)00462-7

Cited by 20 publications

(11 citation statements)

References 9 publications

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“…Declines of 40 -50% have been depicted in American and European men (Becker and Berhane, 1997;Carlsen et al, 1992). Further analysis has disclosed that sampling biases Saidi et al, 1999), changes in clinical norms (Bromwich et al, 1994), variation in quantitative methods (Emanuel et al, 1998), and unsuitable statistical analyses (Olsen et al, 1995) may underlie many of the reported differences. In addition, there is no reason to believe that according to clinical standards, any compromise in male fecundity has occurred, even if these declines are valid.…”

Section: Sperm Countmentioning

confidence: 99%

Reproductive ecology and life history of the human male

Bribiescas

2001

Am. J. Phys. Anthropol.

211

117

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Until recently, the reproductive ecology of human males has not been extensively investigated, primarily as a result of the need for a theoretical framework based on the reproductive constraints and energetics of mammalian males. More specifically, male reproductive ecology has necessitated an integrative interpretation of clinical and anthropological data based on the premise that the evolution of human male life histories has involved selection for physiological mechanisms aimed at optimizing trade-offs between survivorship and reproductive effort. This paper attempts to address this gap in our understanding by presenting the current state of male reproductive ecology, including physiologic data from clinical and anthropological investigations as well as recent theoretical developments. Recent investigations outlining population variation in reproductive endocrine function are discussed within the context of potential sources of variation, including energetic expediture, caloric intake, and developmental canalization during adolescence. Additional summaries of male senescence and behavior are presented to provide a complete overview of male life history. Implications of recent anthropological data on contemporary health issues such as prostate cancer and the development of a male contraceptive are also discussed. Finally, several theories are presented that may contribute to our understanding of the evolution of male life histories and reproductive ecology, including theoretical suggestions involving the role of competition, mate choosiness, and potential constraints on male insemination ability, as well as a theory suggesting that male reproductive ecology may be best understood by analyzing energetic allocation decisions between differing somatic tissues that may be indicative of the competing needs for optimizing survivorship and reproductive effort. Directions for future research are finally considered.

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Section: Sperm Countmentioning

confidence: 99%

Reproductive ecology and life history of the human male

Bribiescas

2001

Am. J. Phys. Anthropol.

211

117

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“…[1][2][3][4][5][6][7][8] By contrast, other studies have shown no evidence of deteriorating semen quality. [9][10][11][12][13][14][15][16] Some studies concern infertile couples, while others analyse normal sperm parameters. Thus, a worldwide decreasing trend in semen parameter values can be neither confirmed nor rejected.…”

Section: Introductionmentioning

confidence: 99%

Decline of semen quality among 10 932 males consulting for couple infertility over a 20-year period in Marseille, France

Geoffroy-Siraudin¹,

Loundou²,

Romain³

et al. 2012

Asian J Androl

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Semen from 10 932 male partners of infertile couples was analysed and sperm parameter trends were evaluated at the Reproduction Biology Laboratory of the University Hospital of Marseille (France) between 1988 and 2007. After 3-6 days of abstinence, semen samples were collected. Measurements of seminal fluid volume, pH, sperm concentration, total sperm count, motility and detailed morphology of spermatozoa were performed. Sperm parameters were analysed on the entire population and in men with normal total numeration (o40 million per ejaculate). The whole population demonstrated declining trends in sperm concentration (1.5% per year), total sperm count (1.6% per year), total motility (0.4% per year), rapid motility (5.5% per year) and normal morphology (2.2% per year). In the group of selected samples with total normal sperm count, the same trends of sperm quality deterioration with time were observed. Our results clearly indicate that the quality of semen decreased in this population over the study period. Keywords: environment; male infertility; regional differences; semen quality; sperm parameters INTRODUCTION Numerous studies suggest a decline in semen quality in some parts of the world. 1-8 By contrast, other studies have shown no evidence of deteriorating semen quality. 9-16 Some studies concern infertile couples, while others analyse normal sperm parameters. Thus, a worldwide decreasing trend in semen parameter values can be neither confirmed nor rejected. 17 It was recently reported that fecundity is affected by this decrease. 18,19 It was speculated that decreasing sperm parameters are in response to adverse environmental factors. Nevertheless, the observed discrepancies between studies suggest regional differences in semen quality. [20][21][22] Variations in environmental factors, industrial pollution and/or lifestyle could explain these discrepancies. A large number of environmental factors can pollute air, drinking water and food. This can directly alter the male gonad by blood-testis barrier disruption and cellular toxicity, or disrupt androgen biosynthesis and action. Among these environmental factors, oestrogenic or anti-androgenic endocrine disrupting compounds inhibit critical cellular process controlling steroidogenesis in Leydig cells and androgen binding to the androgen receptor. 23 It has been hypothesized that endocrine disrupting compounds play a major role in the aetiology of increased incidence of testicular dysgenesis syndrome which gathers decreased quality of semen, cryptorchidism, hypospadias and testicular cancer. 24 Chemicals with hormone-like activity can also

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“…Although the paper generated a great deal of media attention, it has been repeatedly criticized in the scientific community for its many methodological flaws. [9][10][11][12][13] These flaws include: high cross-study variability in the methods and protocols used for sperm collection and measurement; lack of control for period of abstinence, cigarette smoking or recreational drug use; failure to include some studies reporting no decline in semen parameters; and failure to account for geographic variation between studies.…”

Section: Critical Analysis Of An Influential Papermentioning

confidence: 99%

“…When these tools are applied to the Carlsen data, mean sperm concentrations have actually increased since 1940. 12 In the two decades since publication of Carlsen's paper, at least 35 major studies of time trends in semen parameters have been published. Eight (on a total of 18 109 men) suggest a decline in semen parameter values (Table 1); 21 (on a total of 112 386 men) show either no change or an increase in semen quality ( Table 2); and six (on a total of 26 007 men) show ambiguous or conflicting results ( Table 3).…”

Section: Critical Analysis Of An Influential Papermentioning

confidence: 99%

Trends in global semen parameter values

Fisch¹,

Braun²

2013

Asian J Androl

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llegations for a worldwide decline in semen parameter values have not withstood scientific scrutiny. Methodological flaws in an influential 1992 paper are summarized here, and studies that have been published since 1992 are reviewed. Of the 35 major studies of time trends in semen quality reviewed here, eight (a total of 18 109 men) suggest a decline in semen quality; 21 (112 386 men) show either no change or an increase in semen quality; and six (26 007 men) show ambiguous or conflicting results. The cause (or causes) of the geographical and temporal variations in semen parameter values reported by these diverse studies deserve further investigation.This paper critically examines two related scientific assertions: that there have been worldwide declines in semen quality in recent decades and that these declines are related to environmental exposure to minute levels of 'endocrine disruptors' (chemicals that exhibit some degree of estrogen-like activity in the body). The data supporting these assertions will be demonstrated to be weak, at best. Reported declines in semen parameter values are likely to be either highly local phenomena with an unknown etiology or the result of methodological errors arising from attempts to observe highly variable physical attributes (semen characteristics) with relatively lowresolution tools (retrospective analysis of nonrandomized study populations). METHODOLOGICAL CHALLENGESFor many reasons, semen may be the most poorly understood bodily fluid, in terms of the distribution of its normal values in the general population. One problem is the relative difficulty of obtaining human semen for scientific analysis. The fact that semen is most readily obtained by masturbation poses significant logistical barriers to objective, randomized, longitudinal studies of semen parameters in community-dwelling men. For example, participation rates in the few studies that have attempted to assess semen quality in non-infertile men have typically been ,20%).

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Macleod Revisited: Sperm Count Distributions in 374 Fertile Men From 1971 to 1994

Cited by 20 publications

References 9 publications

Reproductive ecology and life history of the human male

Reproductive ecology and life history of the human male

Decline of semen quality among 10 932 males consulting for couple infertility over a 20-year period in Marseille, France

Trends in global semen parameter values

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