COMMENTARY

The Male Biological Clock – How to Tell the Time

Mark P. Trolice, MD

October 26, 2021

For decades, we have recognized the age-related natural decline in female fecundity (the ability to reproduce) after the age of 30 (Maturitas 1988;[Suppl]1:15-22). Advanced maternal age (AMA) has also been demonstrated to increase miscarriage and pregnancies with chromosomal abnormalities, presumably from the increased rate of oocyte aneuploidy. There has been a sixfold increase in the rate of first birth in women aged 35-39 years (NCHS Data Brief 2014;152:1-8). Consequently, over the last decade, women, often before they reach AMA, have turned to elective oocyte cryopreservation for fertility preservation.

Ovarian Aging

Ovarian aging occurs through the decline in quality and quantity of oocytes. The former is a reflection of the woman's chronologic age. Markers of female ovarian aging have been utilized, for the past 3 decades, most commonly by basal follicle stimulating hormone. Currently, to assess the quantity of ovarian follicles, antimüllerian hormone (AMH) and transvaginal ultrasound for ovarian antral follicle count (AFC) are the most accurate indicators (J Clin Endocrinol Metab 2004:89:2977-81). While ovarian age testing, particularly AMH, has been widely used to assess a woman's “fertility potential,” it does not reflect her natural fecundity. In a prospective cohort study, AMH levels (ng/mL) divided into < 0.7, 0.7-8.4, and > 8.4, did not affect natural conception in women aged 30-44 who were divided into the categories of <35, 35-37, or 38-44 years (JAMA 2017;318:1367-76). Although AMH does reduce success with IVF, its main value is the inverse correlation when prescribing gonadotropin dosage for controlled ovarian stimulation.

Despite the familiarity with ovarian aging effects on fertility, the male biological clock remains less studied and understood. Over the last 4 decades, paternal age has increased an average of 3.5 years presumably due to delayed child rearing from professional or personal reasons, improved contraception as well as increased divorce, remarriage, and life expectancy (Hum Reprod. 2017;32:2110-6). Nevertheless, we have little data to definitively counsel men on the effects of advanced paternal age (APA) and no consensus on an actual defined age of designation. This month's article will summarize the current literature on male age and its impact on fertility.

Testicular Aging

Men older than 45 years require approximately five times longer to achieve a pregnancy as men less than 25 after adjustment for female age (Fertil Steril. 2003;79:1520-7). The most likely parameter to assess male fertility, other than pregnancy rates, would be the sperm. Sperm counts, beginning at age 41, may decline but concentrations have been shown to increase in older men apparently because of declining semen volume (Ageing Res Rev. 2015;19:22-33). Sperm motility, but not morphology, also declines while genetic alterations of sperm increase with age. The issue of chromosomal abnormalities in sperm from men of advanced age appears to be similar to that in the oocytes of women with AMA. Consequently, both sexes may contribute to embryo aneuploidy resulting in declining fertility and increasing miscarriage.

For all ages, studies have suggested that elevated male body mass index as well as alcohol consumption and cigarette smoking, including e-cigarettes, can lead to impaired sperm production (Hum Reprod Update 2013;19:221-31).

Fertility Treatment Outcomes

A mainstay of fertility treatment, particularly in men with mild to moderate impairments in semen parameters, is ovulation induction with intrauterine insemination. Male age has been shown to be a significant indicator for pregnancy rates, including those with normal semen parameters (J Obstet Gynaecol. 2011;31:420-3). Men above age 45 contributed to lower pregnancy rates and higher miscarriages during IUI treatment cycles (Reprod BioMed Online 2008;17:392-7).

During IVF cycles, the sperm of men with APA often undergo ICSI (intracytoplasmic sperm injection) due to higher fertilization rates compared with standard insemination. However, APA sperm appear to have lower fertilization rates and decreased embryo development to the blastocyst stage during cycles using donor oocytes, although pregnancy outcomes are inconsistent (Trans Androl Urol. 2019;8[Suppl 1]:S22-S30; Fertil Steril. 2008;90:97-103).

Perinatal and Children's Health

The offspring from APA men appear to have higher rates of stillbirth, low birth weight, and preterm birth, as well as birth defects. Men older than 40-45 years have twice the risk of an autistic child and three times the risk of schizophrenia in their offspring (Transl Psychiatry 2017;7:e1019; Am J Psychiatry 2002;159:1528-33).

Conclusions

Most of the literature supports negative effects on sperm and reproduction from men with APA. The challenge in deciphering the true role of APA on fertility is that the partner is often of AMA. A consideration to avoid this effect would be sperm cryopreservation at a younger age, similar to the common trend among women. Preimplantation genetic testing of embryos from men with APA is also a potential option to reduce miscarriage and avoid a chromosomally abnormal pregnancy. Ethicists have pondered the impact of APA on parenthood and the detrimental effect of early paternal death on the child. Nevertheless, the effect of APA in reproduction is a vital area to study with the same fervor as AMA (Fertil Steril 2009;92:1772-5).

Trolice is director of Fertility CARE – The IVF Center in Winter Park, Fla., and professor of obstetrics and gynecology at the University of Central Florida, Orlando. He has no conflicts. Email him at obnews@mdedge.com.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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