‘Biological clock’ isn’t just for women: Doctor explains male fertility also declines with age

Men have a ‘biological clock’ too – here’s why male fertility declines with age and what couples planning parenthood should know.

Men may not experience fertility decline as abruptly as women do, but that does not mean age has no impact. The changes in sperm quality and certain reproductive outcomes do take place with age. In an interview with HT Lifestyle, Dr Hrishikesh Pai, medical director and co-founder of Bloom IVF, answers everything about men’s biological clocks.

1. At what age does male fertility start declining and why is that surprising?

Dr Hrishikesh highlights that subtle decline begins in the mid-30s and becomes measurable by 40–45. We see falling sperm motility, worsening morphology, and most importantly, rising sperm DNA fragmentation. It surprises people because men keep producing sperm lifelong, unlike the finite oocyte pool in women. But continuous production doesn't mean quality is preserved; the germline stem cells accumulate replication errors with every division.

In male subtle decline begins in the mid-30s and becomes measurable by 40–45. (Unsplash)

2. Does paternal age affect the child's health?

Yes, and this is under-appreciated. “Older fathers transmit more de novo mutations, roughly two additional new mutations per year of paternal age,” said Dr Hrishikesh. This correlates with modestly elevated risk of autism spectrum disorders, schizophrenia, and single-gene conditions such as achondroplasia and Apert syndrome. Advanced paternal age also lowers live-birth rates in ART and raises miscarriage risk, independent of maternal age.

3. Why has the "biological clock" stayed focused on women?

This is because menopause is a visible, hard endpoint, whereas male decline is gradual and clinically silent. That framing costs couples real time: they attribute failed conception or recurrent miscarriage solely to the woman, delaying male evaluation. Dr Hrishikesh highlighted that unexamined male-factor issues, especially high DNA fragmentation, are a common reason for repeated IVF failure that could have been addressed earlier.

4. What factors quietly accelerate male decline?

Chronic scrotal heat (laptops, saunas, tight clothing, occupational exposure) impairs spermatogenesis. Obesity raises scrotal temperature and shifts testosterone toward estrogen. Smoking and alcohol drive oxidative DNA damage. Endocrine disruptors such as phthalates, BPA, certain pesticides, interfere with hormonal signalling. Chronic psychological stress suppresses the hypothalamic-pituitary-gonadal axis. Individually modest, these are cumulative and, crucially, largely reversible.

Smoking and alcohol drive oxidative DNA damage. (Unsplash)

5. Should fertility testing be routine in men's checkups?

A universal screen isn't yet cost-justified, but I'd argue strongly for a low threshold — men over 35 planning a family, or any couple with conception difficulty, should have a semen analysis early rather than as a last resort. It's inexpensive, non-invasive, and often the fastest route to a diagnosis. Normalising it would remove stigma and spare couples’ months of misdirected investigation.

Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. Always seek the advice of your doctor with any questions about a medical condition.