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.

https://www.bmj.com/content/bmj/305/6854/609.full.pdf

Evidence for decreasing quality of semen during past 50 years.

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). ...

Decline in Semen Quality among Fertile Men in Paris during the Past 20 Years

/pdf/evidence-for-decreasing-quality-of-semen-during-past-50-vlioqbfqzo.pdf

Evidence for Decreasing Quality of Semen During Past 50 Years

In 1992 a worldwide decline in sperm density was reported; this was quickly followed by numerous critiques and editorials. Because of the public health importance of this finding, a detailed reanalysis of data from 61 studies was warranted to resolve these issues. Multiple linear regression models (controlling for abstinence time, age, percent proven fertility, specimen collection method, study goal and location) were used to examine regional differences and the interaction between region (United States, Europe, and non-Western countries) and year. Nonlinear models and residual confounding were also examined in these data. Using a linear model (adjusted R2 = 0. 80), means and slopes differed significantly across regions (p = 0. 02). Mean sperm densities were highest in Europe and lowest in non-Western countries. A decline in sperm density was seen in the United States (studies from 1938-1988; slope = -1.50; 95% confidence interval (CI), -1.90--1.10) and Europe (1971-1990; slope = -3.13; CI, -4.96- -1.30), but not in non-Western countries (1978-1989; slope = 1.56; CI, -1.00-4.12). Results from nonlinear models (quadratic and spline) were similar. Thus, further analysis of these studies supports a significant decline in sperm density in the United States and Europe. Confounding and selection bias are unlikely to account for these results. However, some intraregional differences were as large as mean decline in sperm density between 1938 and 1990, and recent reports from Europe and the United States further support large interarea differences in sperm density. Identifying the cause(s) of these regional and temporal differences, whether environmental or other, is clearly warranted.

Have sperm densities declined? A reanalysis of global trend data.

Semen analyses in 1,283 men from the United States over a 25-year period: no decline in quality

Semen parameters of 135 randomly selected men in 1966 were compared with semen analysis of 148 men in 1986 to assess whether semen characteristics had changed during the period. Both groups of men were of barren couples; median age was identical in the two groups (31 years). The semen analyses included volume, sperm density, and sperm morphology. Significant change over the time period was observed only for the percentage of normal morphology. This parameter deteriorated from 60% in 1966 to 41% in 1986 (median values; p less than .001). This study, like studies from other industrialized countries, indicates a decline in semen quality over the past decades.

E Bendvold

Papers

Semen quality in Norwegian men over a 20-year period.