Desarrollo De La Investigacion Productividad De Semen Del Verraco

FERTILITY AND STERILITY
VOL. 75, NO. 2, FEBRUARY 2001
Copyright ©2001 American Society for Reproductive Medicine
Published by Elsevier Science Inc.
Printed on acid-free paper in U.S.A.

MODERN TRENDS
Edward E. Wallach, M.D.
Associate Editor

Effects of male age on semen quality and
fertility: a review of the literature
Sharon A. Kidd, M.P.H.,a Brenda Eskenazi, Ph.D.,a and Andrew J.Wyrobek, Ph.D.b
University of California, Berkeley, and Lawrence Livermore National Laboratory, Livermore, California

Objective: To review the literature on the association between male age and semen quality (semen volume,
concentration, motility, and morphology) and fertility status (pregnancy rate and time to pregnancy/subfecundity).
Method(s): Review of English language–published researchover the last 20 years from January 1, 1980,
through December 31, 1999, using MEDLINE and Biosis databases. Studies with insufficient numbers of
subjects, case reports, case series, or anecdotal data were excluded.
Result(s): Among the methodologically stronger studies, decreases in semen volume of 3%–22%, decreases
in sperm motility of 3%–37%, and decreases in percent normal sperm of 4%–18%were likely when
comparing 30-year-old men to 50-year-old men. Most studies examining fertility status suggest a relationship
between male age and fertility, but the results are most likely confounded by female partner age. Among
studies that did control for female age, comparisons between men under 30 and men over 50 found relative
decreases in pregnancy rates between 23% and 38%. A comparisonof the various age categories showed that
the increased risks for subfecundity ranged from 11% to 250%.
Conclusion(s): The weight of the evidence suggests that increased male age is associated with a decline in
semen volume, sperm motility, and sperm morphology but not with sperm concentration. (Fertil Steril 2001;
75:237– 48. ©2001 by American Society for Reproductive Medicine.)
Key Words:Human male, age, semen, volume, concentration, motility, morphology, pregnancy, fertility,
review

Received August 18, 2000;
revised and accepted
September 11, 2000.
Funded by NIEHS
Superfund P42ES04705
and conducted in part
under the auspices of the
US DOE by Lawrence
Livermore National
Laboratory under contract
W-405-ENG-48.
Reprint requests: Brenda
Eskenazi, Ph.D., 2150
ShattuckAvenue, Suite
600, Berkeley, CA 947207380 (FAX: 510-642-9083).
a
School of Public Health,
University of California,
Berkeley.
b
Biology and
Biotechnology Research
Program, Lawrence
Livermore National
Laboratory.
0015-0282/01/$20.00
PII S0015-0282(00)01679-4

Infertility has a major public health impact,
with approximately 15% of couples of reproductive age in the United Statesreceiving infertility services at some point in their lives (1),
and approximately 7% of married couples not
being able to conceive after trying for a year
(2). Reduced fertility typically occurs among
women in their late 30s to early 40s, when
there is a sharp decrease in oocyte production
(3). However, 25% or more of infertility is
attributed to male factors (1).
Since 1980, there has been inthe United
States a 16% increase in the birth rate for
fathers over age 35 (4). Unlike women, who
are more fertile below the age of 40, men can
conceive children well beyond their 40s and
there is no known critical threshold with respect to sperm production in men. Nevertheless, it is important to know whether advanced
paternal age is associated with diminished semen quality and a higherrisk of infertility.
Rats and mice are good animal models for
investigating the mechanisms of reproductive

aging in males (5, 6). Aging of rodents appears
to be related to histologic changes in the testes
and in declines in sperm quality. Tanemura et
al. (5) reported that vacuoles appeared in germ
cells and cell numbers decreased in older mice
(18 months old), resulting in a thinner...