The average man's sperm count has dwindled by 59% in Western countries over the last four decades, reported The New York Times.
That was the finding of a meta-analysis of 185 studies -- covering 40,000 men in 50 countries -- that found a similar reduction in sperm counts per milliliter of semen.
Men from non-Western countries in South America, Africa, and Asia, who made up 25% of study participants, did not show a significant decline in sperm quality. However, sperm counts dropped in some developing countries including China.
Researchers attributed the regional differences to the prevalence of endocrine-disrupting chemicals such as phthalates. Cigarette smoke, alcohol, age, stress, and obesity have also been linked to lower sperm counts.