Several large-scale research studies show that sperm counts decline during the hot summer months and recover during the fall and winter. Let’s explore how higher temperature and longer days may contribute to reduced sperm count.
Sperm are much more sensitive to heat than any other cell in the body. Temperatures above about 95⁰F activate a protein called Heat Shock Factor in developing sperm. If sperm are exposed to temperatures above 95⁰F for long periods of time, Heat Shock Factor will cause the sperm to die before they are mature. In comparison, other cells in your body won’t activate Heat Shock Factor until they reach temperatures higher than 105⁰F (which is why fevers above 105⁰F are considered dangerous). Because your sperm are much more sensitive, extended exposure to heat can cause a dip in your sperm count while the rest of your body feels fine.
Researchers have also studied how testosterone levels change throughout the year. Testosterone peaks in the morning following a good night’s sleep. Longer days or other changes to sleep habits during the summer months can decrease testosterone levels, which in turn can impact sperm production.