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Evidence for decreasing quality of semen during past 50 years
E Carlsen1, A Giwercman, N Keiding
1University Department of Growth and Reproduction, Rigshospitalet, Copenhagen.
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.
Insights
Semen quality has significantly declined over the past 50 years, with sperm count and volume decreasing substantially. This trend may indicate a broader reduction in male fertility and reproductive health.
Area of Science:
- Reproductive Biology
- Environmental Health
- Epidemiology
Background:
- Semen quality is a key indicator of male reproductive health.
- Investigating historical trends in semen parameters is crucial for understanding population-level fertility changes.
- Potential environmental or lifestyle factors may influence male reproductive outcomes over time.
Purpose of the Study:
- To determine if semen quality has changed in men over the last half-century.
- To analyze trends in sperm density and seminal volume.
- To assess the potential implications of observed changes for male fertility.
Main Methods:
- A comprehensive review of 61 published studies encompassing 14,947 men without a history of infertility.
- Data collection spanned from 1938 to 1991, utilizing historical databases (Cumulated Index Medicus, Current List) and MEDLINE.
- Statistical analysis employed linear regression, weighting data by the number of men in each study.
Main Results:
- A significant decrease in mean sperm density was observed, from 113 x 10^6/ml in 1940 to 66 x 10^6/ml in 1990 (p < 0.0001).
- Mean seminal volume also declined significantly, from 3.40 ml to 2.75 ml (p = 0.027) over the same period.
- The reduction in seminal volume suggests a more pronounced decrease in overall sperm production than indicated by sperm density alone.
Conclusions:
- A genuine decline in human semen quality has occurred over the past 50 years.
- The observed decrease in sperm count and volume may correlate with a reduction in male fertility.
- Concomitant increases in genitourinary abnormalities suggest environmental factors may be impacting male reproductive health.