Science Weekly ‘Spermageddon’: is male fertility really in crisis?
Jul 4, 2024
The guest, Nicola Davis, discusses the global reproductive crisis and the conflicting studies on declining sperm counts. They explore potential causes like genetic conditions, lifestyle factors, and microplastic contamination. The podcast emphasizes the need for continued research on male fertility.
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Large Meta-Analyses Report Big Long-Term Sperm Declines
- Two major meta-analyses led by Israeli researchers found sperm concentration fell ~52%–101.2 to 49 million/ml and total sperm count dropped ~60% from 1973–2018.
- These pooled studies used many smaller cohorts (students, military recruits, fathers) to reveal large long-term declines that sparked the "spermageddon" debate.
Recent Danish Donor Data Challenges Universal Decline
- A Danish sperm-donor study (2017–2022) found no major decline in sperm counts but slight falling motility, challenging the universality of the meta-analyses.
- The donor sample may be biased (younger, healthier) and covers only recent years and a small region, so it might reflect a plateau rather than reversal.
Population Averages Can Mask Clinical Risk
- Average sperm concentrations can decline substantially yet remain above infertility thresholds; NHS defines low sperm count as <15 million/ml.
- The 2022 meta-analysis average fell from ~101.2 to 49 million/ml, still above the NHS low-count cutoff, though more men might now fall below it.