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It is well known that women age is important for reproduction. The female biological clock is well-defined temporally and biologically, with declining oocyte production when the woman is in her late 30s or early 40s and cessation of menses in the late 40s and early 50s. Whereas woman’s chances to conceive naturally drop sharply, male fertility does not cease abruptly, since androgen production and spermatogenesis continue throughout life. There are some worldwide-known examples of famous personalities who fathered children at an advanced age, like Julio Iglesias´s senior (90), Luciano Pavarotti (68) or Rod Stewart (66).

A great problem in our society and that of industrialized countries is that couples wait longer to have children, and advances in reproductive technology currently allow older men and women to consider being parents. However, many studies highlight age as an important factor to conceive in both sexes. During years, fertility research has focused mainly on women age, and so potential adverse effects of male age might have passed unnoticed. However, there is currently great concern about the decreasing quality of sperm with age in men. In 2010, the World Health Organisation (WHO) changed criteria to semen evaluation, due to a decreased concentration and normal sperm morphology below the threshold for which a semen sample was considered of good quality.

Table 1. Changes in seminal quality assessment criteria (9, 10).
On the other hand, some research lines show that in men, advanced age affects sperm quality (decreases semen volume and reduces the percentage of normal sperm morphology and motility). It also affects non-reproductive physiological issues such as libido or erectile functionBlood testosterone levels decline with age in most men, even in healthy ones; this decline probably begins around the age of thirty, which has been termed andropause. So, similarly to women, ageing in men is also associated with a drop in sex hormone levels; therefore, we can talk about an effective male biological clock. These changes in sex hormone levels and sperm quality could affect fertility, because sperm genetic material is altered and, as a consequence, the risk of spontaneous abortion is increased due to offspring genetic abnormalities.

IS AGE IN MEN ASSOCIATED WITH DIFFERENT OFFSPRING DISEASES OR LIVE BIRTH RATES?

These alterations could explain the association of paternal age with the increased incidence of some psychiatric disorders such as those of the autism spectrum, psychosis, schizophrenia and bipolar disorders at childbearing. Moreover, there seems to be supporting evidence that paternal age significantly influences the incidence of having a child with Down syndrome when combined with maternal age. This could also be the case for other genetic abnormalities, which could in turn lead to miscarriage or different diseases in the newborns.

Finally, It has been demonstrated that men over 35 years old are twice as likely to be infertile (defined as the inability to achieve a pregnancy within 12 months).

Figure 1. Percentage of live births by age of father (4).
A recent study reported at European Society of Human Reproduction and Embryology congress in July 2017 found that couples with both members under 30 had around 70% chance of having a live birth after an in vitro fertilization cycle. However, that success rate fell to around 50% when the man was aged 40-42.

CONCLUSIONS

In summary, age is an important factor both in women and in men, but It should also be taken into consideration that there are other factors such as obesity, habitual alcohol and/or tobacco intake and stress, among other well-studied elements, which might be effectively altering our fertility potential.

Currently available data not only show that male biological clock does exist, but it is also important to fertility. Mechanisms of action are unclear, but as above-exposed, they might involve impaired semen parameters and increased levels of damaged sperm DNA, which could affect fertilization, implantation and even embryo development.

REFERENCES

  1. D’Onofrio BM, Rickert ME, Frans E, Kuja-Halkola R, Almqvist C, Sjölander A, et al. Paternal age at childbearing and offspring psychiatric and academic morbidity. JAMA Psychiatry. 2014;71(4):432-8.
  2. Dodge L, Penzias A, Hacker M. The impact of male partner age on cumulative incidence of live birth following in vitro fertilization. Oral communication at the ESHRE. 2017.
  3. Eskenazi B, Wyrobek AJ, Sloter E, Kidd SA, Moore L, Young S, et al. The association of age and semen quality in healthy men. Hum Reprod. 2003;18(2):447-54.
  4. Fisch, H. The male biological clock. In: D. Carrell, ed. Paternal Influences on Human Reproductive Success. New York: Cambridge University Press, 2013. pp.61-69.
  5. Fisch, H, Braun S. In: Simon and Schuster, ed. The male biological clock. The startling news about aging, sexuality, and fertility in man. New York: Free press, 2005. p.10.
  6. Fisch H, Hyun G, Golden R, Hensle TW, Olsson CA, Liberson GL. The influence of paternal age on down syndrome. J Urol. 2003;169(6):2275-8.
  7. Harris ID, Fronczak C, Roth L, Meacham RB. Fertility and the aging male. Rev Urol. 2011;13(4):e184-90.
  8. Pasqualotto FF, Borges Júnior E, Pasqualotto EB. The male biological clock is ticking: a review of the literature. Sao Paulo Med J. 2008;126(3):197-201.
  9. WHO laboratory manual for the examination and processing of human semen- 5th ed. In:  Geneva: WHO Press, 2010.
  10. WHO laboratory manual for the examination of human semen and sperm-cervical mucus interaction- 4th ed. In: Cambrige University Press, 1999.