Are Sperm Characteristics Seasonal?

With Fall coming up at the end of the month, learn more about seasonality and sperm.

Temperature and weather are usually talked about when referring to seasons. For example, summers tend to be warmer while winters are colder. When talking about male fertility, the temperature is also a topic that may come up. For example, men may be told to avoid hot baths and saunas because of the potential impact of this high heat on sperm.

There have been a number of studies that have looked at the correlation between scrotal temperature and sperm quality and count. One study looked at occupational heat exposure and concluded that “heat exposure is a significant risk factor for male infertility, affecting sperm morphology and resulting in delayed conception.” Because of the correlation between temperature and heat, some have questioned whether temperature, as dictated by seasons, has an impact on male fertility.

There are four seasons in a year (Spring, Summer, Fall, and Winter), and they are a result of Earth’s orbit around the Sun and orbit and also Earth’s tilt. Each year the seasons come and go, and depending on where you live, you may feel and experience them more drastically.

There have been a number of studies that have looked into the connection between seasonality and sperm.  For example, research presented at the 2018 American Society for Reproductive Medicine meeting found that sperm counts tend to be highest in the Fall and Spring and lowest in the Summer—This research led by Dr Taraneh Nazem of the Icahn School of Medicine at Mount Sinai looked at samples from 29,000 men over 17 years. The lead researcher said that “'it is possible that male fertility is better in these seasons but further research is needed to know how these findings affect pregnancy success rates.”

A 2003 study also looked at seasonal variation--along with age—on semen characteristics. This study found that “Seasonal variations were found in sperm concentration and morphology, with higher sperm concentrations in winter than in fall, and a greater percentage of sperm with normal morphology in winter than in spring and summer.”

Daytime hours, exercise, diet, drinking, holidays, and temperature may all play into seasonality and impact on sperm characteristics, and more research is needed to determine the impact of seasons on male fertility.