Macleod Revisited: Sperm Count Distributions in 374 Fertile Men From 1971 to 1994
TL;DR: Sperm counts in fertile men have not changed appreciably in the 40 years since MacLeod's report, and remarkable similarities in sperm count distributions in cohorts of fertile men from 1951 and 1971 to 1994 are found.
About: This article is published in Urology.The article was published on 1998-01-01. It has received 21 citations till now. The article focuses on the topics: Sperm & Vasectomy.
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TL;DR: The current state of male reproductive ecology is presented, including physiologic data from clinical and anthropological investigations as well as recent theoretical developments, and several theories are presented that may contribute to the understanding of the evolution of male life histories and reproductive ecology.
Abstract: 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.
213 citations
TL;DR: Focusing on the subgroup of men with normal semen quality showed that sperm count and sperm progressive motility were inversely related to the concentrations of PCB metabolites within this group, the first time that a correlation between exposure to environmental pollutants with endocrine-disrupting capacity and human sperm quality has been observed.
Abstract: BACKGROUND: Various studies have been performed in which potential effects of xenoestrogens on fertility or sperm parameters were investigated by comparing groups of subjects exposed to different levels of these chemicals. METHODS: In our study we used an alternative approach, as we selected one group of men with very poor semen quality and another group with normal semen quality and determined the blood organochlorine contents in order to determine whether a difference in these levels could be established. Organochlorine compounds, including polychlorinated biphenyls (PCB) and PCB metabolites, were detected using gas chromatography. The concentrations were compared between both groups, and related to semen parameters. RESULTS: A comparison of both groups did not reveal significant differences in organochlorine levels. Linear relationships were found when PCB and metabolite concentrations were related to the age of the volunteers. Focusing on the subgroup of men with normal semen quality showed that sperm count and sperm progressive motility were inversely related to the concentrations of PCB metabolites within this group. CONCLUSIONS: The finding of a significantly decreased sperm count in relation to an elevated PCB metabolite level within the subgroup of men with normal semen quality is important. This is the first time that a correlation between exposure to environmental pollutants with endocrine-disrupting capacity and human sperm quality has been observed.
183 citations
Cites background from "Macleod Revisited: Sperm Count Dist..."
...However, since the publication of a meta-analysis of 61 studies concerning human sperm count (Carlsen et al., 1992), the decline in male fertility has been extensively examined and disputed (Bromwich et al., 1994; Auger et al., 1995; Olsen et al., 1995; Bujan et al., 1996; Fisch et al., 1996; Irvine et al., 1996; Paulsen et al., 1996; Becker and Berhane, 1997; Swan et al., 1997, 2000; Emanuel et al., 1998; Saidi et al., 1999)....
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TL;DR: The impetus for a comprehensive re-evaluation at this time is the potential impact of a real decline in semen quality and subsequent human fertility, and confusion and misinformation about semen quality remain widespread in lay and professional circles.
95 citations
TL;DR: The results clearly indicate that the quality of semen decreased in this population over the study period and the same trends of sperm quality deterioration with time were observed.
Abstract: 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 (≥40 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.
81 citations
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TL;DR: There has been a genuine decline in semen quality over the past 50 years, and as male fertility is to some extent correlated with sperm count the results may reflect an overall reduction in male fertility.
Abstract: OBJECTIVE--To investigate whether semen quality has changed during the past 50 years. DESIGN--Review of publications on semen quality in men without a history of infertility selected by means of Cumulated Index Medicus and Current List (1930-1965) and MEDLINE Silver Platter database (1966-August 1991). SUBJECTS--14,947 men included in a total of 61 papers published between 1938 and 1991. MAIN OUTCOME MEASURES--Mean sperm density and mean seminal volume. RESULTS--Linear regression of data weighted by number of men in each study showed a significant decrease in mean sperm count from 113 x 10(6)/ml in 1940 to 66 x 10(6)/ml in 1990 (p < 0.0001) and in seminal volume from 3.40 ml to 2.75 ml (p = 0.027), indicating an even more pronounced decrease in sperm production than expressed by the decline in sperm density. CONCLUSIONS--There has been a genuine decline in semen quality over the past 50 years. As male fertility is to some extent correlated with sperm count the results may reflect an overall reduction in male fertility. The biological significance of these changes is emphasised by a concomitant increase in the incidence of genitourinary abnormalities such as testicular cancer and possibly also cryptorchidism and hypospadias, suggesting a growing impact of factors with serious effects on male gonadal function.
2,481 citations
TL;DR: The volume of seminal fluid, the sperm concentration, and the percentages of motile and morphologically normal spermatozoa in 1351 healthy fertile men from 1973 through 1992 were measured.
Abstract: Background Several studies have suggested a population-wide decline in the quality of semen over the past 50 years, but clear evidence of decreasing semen quality in recent decades is lacking. Methods From 1973 through 1992 we measured the volume of seminal fluid, the sperm concentration, and the percentages of motile and morphologically normal spermatozoa in 1351 healthy fertile men. The data on the semen samples were collected at one sperm bank in Paris. The data in each calendar year were analyzed as a function of the year of donation, the age of each patient, the year of birth, and the duration of sexual abstinence before semen collection. Results There was no change in semen volume during the study period. The mean concentration of sperm decreased by 2.1 percent per year, from 89 ×106 per milliliter in 1973 to 60×106 per milliliter in 1992 (P<0.001). During the same period the percentages of motile and normal spermatozoa decreased by 0.6 percent and 0.5 percent per year, respectively (both P<0.001). ...
1,067 citations
TL;DR: There has been a genuine decline in semen quality over the past 50 years and as male fertility is to some extent correlated with sperm count the results may reflect an overall reduction in male fertility.
Abstract: OBJECTIVE--To investigate whether semen quality has changed during the past 50 years. DESIGN--Review of publications on semen quality in men without a history of infertility selected by means of Cumulated Index Medicus and Current List (1930-1965) and MEDLINE Silver Platter database (1966-August 1991). SUBJECTS--14,947 men included in a total of 61 papers published between 1938 and 1991. MAIN OUTCOME MEASURES--Mean sperm density and mean seminal volume. RESULTS--Linear regression of data weighted by number of men in each study showed a significant decrease in mean sperm count from 113 x 10(6)/ml in 1940 to 66 x 10(6)/ml in 1990 (p < 0.0001) and in seminal volume from 3.40 ml to 2.75 ml (p = 0.027), indicating an even more pronounced decrease in sperm production than expressed by the decline in sperm density. CONCLUSIONS--There has been a genuine decline in semen quality over the past 50 years. As male fertility is to some extent correlated with sperm count the results may reflect an overall reduction in male fertility. The biological significance of these changes is emphasised by a concomitant increase in the incidence of genitourinary abnormalities such as testicular cancer and possibly also cryptorchidism and hypospadias, suggesting a growing impact of factors with serious effects on male gonadal function.
704 citations
TL;DR: Data confirm previously published data from other countries that semen quality is changing, declining by about 2.1% per year Research is urgently required to examine the function as well as the number of sperm and to assess whether these changes are affecting human health and male fertility.
Abstract: Objective: To determine whether the quality of semen has changed in a group of over 500 Scottish men born between 1951 and 1973. Design: Retrospective review of data on semen quality collected in a single laboratory over 11 years and according to World Health Organisation guidelines. Setting: Programme of gamete biology research funded by Medical Research Council. Subjects: 577 volunteer semen donors. Of these, 171 were born before 1959, 120 were born in 1960-4, 171 in 1965-9, and 115 in 1970-4. Main outcome measures: Conventional criteria of semen quality including semen volume (ml), sperm concentration (106/ml), overall motility (% motile), total number of sperm in the ejaculate (106), and total number of motile sperm in the ejaculate (106). Results: When the four birth cohort groups were compared a later year of birth was associated with a lower sperm concentration, a lower total number of sperm in the ejaculate, and a lower number of motile sperm in the ejaculate. The median sperm concentration fell from 98x106/ml among donors born before 1959 to 78x106/ml among donors born after 1970 (P=0.002). The total number of sperm in the ejaculate fell from 301x106 to 214x106 (P=0.0005), and the total number of motile sperm in the ejaculate fell from 169.7x106 to 129.0x106 (P=0.0065). Conclusion: This study provides direct evidence that semen quality is deteriorating, with a later year of birth being significantly associated with a reduced number of sperm in adult life. Key messages Key messages When men born in the 1970s were compared with men born in the 1950s, the total number of motile sperm in the ejaculate was reduced by almost 25% These data confirm previously published data from other countries that semen quality is changing, declining by about 2.1% per year Research is urgently required to examine the function as well as the number of sperm and to assess whether these changes are affecting human health and male fertility
454 citations
TL;DR: The data show no decline in sperm counts over a 25-year period in 1,283 men who banked sperm before vasectomy at three distinct geographical sites in the United States.
379 citations