Declining sperm count

BMJ 1996; 313 doi: https://doi.org/10.1136/bmj.313.7048.43 (Published 06 July 1996) Cite this as: BMJ 1996;313:43

Semen quality has declined among men born in France since 1950

  1. Jacques De Mouzon,
  2. A Spira,
  3. P Thonneau,
  4. L Multigner
  1. Epidemiologist Epidemiologist Epidemiologist Epidemiologist INSERM U 292, Hopital de Bicetre, 94276 Le Kremlin-Bicetre Cedex, France

    EDITOR,—Several recent papers have reported a possible decrease in sperm counts.1 2 3 4 5 Three of them were based on data collected in single laboratories, from a relatively low number of fertile men (between 302 and 1351).1 2 3 Their conclusions were in favour of a decline related to the year of birth1 or to the year of the measurement3 or of no change.2 The two other papers were reviews of the same published papers, the first concluding that sperm counts had decreased and the second that they had increased during the past 20 years.45 The existence of the French national register on in vitro fertilisation enabled us to analyse this phenomenon by using a large database.6 This register, which contains details of 90% of all cycles of in vitro fertilisation in France on an individual basis, has recorded sperm counts since 1989.

    To avoid any bias due to the increasing proportion of in vitro fertilisation that is performed for infertility of male origin, we selected only couples with pure tubal infertility and in which the husband's semen was normal at the examination before in vitro fertilisation was attempted (sperm count >20 million/ml, total motility at 1 hour >40%, and normal morphology >40%). Thus we analysed 19 848 sperm counts (in 7714 men) measured on the day of in vitro fertilisation. Data were analysed with the generalised linear model (SAS Software, SAS Institute, Cary, NC, USA), with both the actual sperm count and the value after logarithmic transformation being analysed.

    The most impressive variations were noted for the year of birth (table 1, since the sperm counts were fairly stable for men born before 1950 and decreased regularly for men born from 1950 to 1975. The decrease was observed whatever the year of collection. When the data were analysed by year of collection a decrease was observed only between 1991 and 1992, the figures being stable before and after these dates. The results were similar when analysis was restricted to the first ejaculates. The period of abstinence was not recorded in the register; for in vitro fertilisation, however, couples are requested to observe two to four days' abstinence before the semen collection.

    Table 1

    Mean (SD) sperm count by year of birth and year of semen collection

    View this table:

    These data clearly suggest a decrease in semen quality among men born in France since 1950. This evidence, concordant with that in the most recent paper on the subject,1 underlines the urgent need for further studies.


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