As a man’s age increases, there’s something in him that decreases: the amount of sperm he has in his system.

According to kompas.com, studies published by the Human Reproduction Update have found that the average amount of male sperm has decreased in the past four decades.

Researchers studied data from 185 studies, which collectively used data from 43,000 male respondents who provided sperm samples from 1971 to 2001. Through the study carried out during this period, researchers found that the total sperm count and concentration had significantly dropped within men in the Western region, which includes North America, Europe, Australia and New Zealand.

Specifically, the average sperm concentration fell by approximately 1.4 percent annually, with a total fall of 52 percent by the end of 2001. Similarly, the average total sperm count fell 1.6 percent annually, with an overall 59 percent decline by the end of the aforementioned period.

These facts show that sperm quality has fallen in recent years, as well as the increasing number of men who may have less fertile sperm.

Furthermore, recent studies have also linked lower sperm counts with male health problems, including a number of illnesses and even premature death.

Unfortunately, this particular study has not gone to the extent of investigating the cause of this phenomenon, but some factors worth noting are environmental influences. These include endocrine disruptors, as well as an unhealthy diet, smoking and increased rates of obesity across the world.

Specifically, diet is one factor that men should pay attention to, as a 2015 study from Taiwan found a connection between decreased sperm concentration with men who have a Western-style diet, meaning a higher consumption of animal protein, processed foods, fats and sugar. Meanwhile, consumption of Omega-3 is connected to the production of better quality sperm.