Authors' replyBMJ 1996; 313 doi: https://doi.org/10.1136/bmj.313.7048.44d (Published 06 July 1996) Cite this as: BMJ 1996;313:44
- Stewart Irvine,
- Elizabeth Cawood,
- John Aitken
- Clinical consultant Scientific officer Professor MRC Reproductive Biology Unit, Centre for Reproductive Biology, Edinburgh EH3 9EW
EDITOR,—Jacques de Mouzon and colleagues' data represent the largest series of retrospective data addressing the question of secular changes in semen quality. They suggest a decline in semen quality with later year of birth, approximating to a 15% fall in sperm concentration when men born in the late 1940s are compared with those born after 1965.
A J P Eccersley and Stephen Farrow are concerned that we combined data from men of proved fertility with data from younger men of unproved fertility. We did so because previous studies1 …