Male fertility is clearly in crisis. A comprehensive review of evidence in 2017, based on 7,500 studies, shows that the average sperm count among Western men have more than halved over the past 40 years. Other studies indicate that as many as 1 in 5 men under 35 has a low sperm count. Illnesses, injuries, chronic health problems, lifestyle choices and other factors can all play a role in causing male infertility. Lifestyle choices can reduce sperm numbers: smoking, drinking alcohol, and taking certain medications can each have a significant impact. The most common problems are associated with the production and growth of sperm. This can mean that sperm doesn’t develop to full size, is oddly shaped, doesn’t travel correctly, is generated in very low numbers (oligospermia) or is not produced at all (azoospermia).