Do you wear tight underwear? Well, if you’re a male, that could be affecting your sperm count. We’ve all heard it before, but apparently the largest comprehensive study of trends in sperm counts verify that they’re at an all time low.

The study spanned 17 years and monitored a sampling of 26,000 males. According to an article in The Independent, the reproductive health of the average male is in sharp decline, as counts have plummeted by one third. While no single reason was given, scientists cite the usual suspects: tight underwear, stress, environmental toxins and diets of highly processed foods.

Scientists say the decrease in sperm counts comes at a time when rates in testicular cancer are on the rise and the two combined signal a crisis.

The implications are not good for those wanting to have children, especially those who wait until later in life, when in general, women have more problems conceiving and maintaining pregnancy. According to the CDC, a woman’s chances of having a baby decrease rapidly every year after the age of 30.

But others maintain that it’s a form of intelligent design. With global population topping 7 billion, this will help slow down that trend.