Ambient climatic conditions and semen quality: a comparative analysis across the periods before, during, and after the COVID-19 pandemic.

Plain-language summary

This study asked whether the pandemic changed how sensitive sperm production is to weather. It took 2,672 semen analyses from 1,287 Korean men collected between 2018 and 2024 and matched each one to local temperature and humidity records for the 90 days before the sample, and separately for the 70 to 90 day window, which is when the earliest stages of that sperm were being made. Two things moved. Sperm concentration and total sperm count rose during the pandemic and stayed higher afterwards, while semen volume fell steadily across the whole period. And heat mattered differently depending on when you looked: hotter weather in the 70 to 90 day window went with lower concentration and total count, but only during the pandemic years. Humidity showed no clear link at any point. Because this is observational, it cannot separate temperature from everything else that changed about how men lived in those years.

Key findings

• Sperm concentration and total sperm count rose during the COVID-19 pandemic and remained higher afterwards.
• Semen volume declined across the whole 2018 to 2024 period.
• Hotter weather 70 to 90 days before a sample went with lower sperm concentration and total count, but only during the pandemic years.
• Humidity showed no clear association with any semen measure.