Male infertility affects roughly 1 in 74 men of reproductive age worldwide, with an estimated 55 million cases globally as of 2021. That number is likely an undercount, since many men never get tested. When couples struggle to conceive, a male factor is involved about half the time, and in roughly 20% of cases, the male partner is the sole cause.
How the Numbers Break Down
About 15% of couples experience infertility, defined as the inability to conceive after a year of regular unprotected sex. For a long time, fertility was treated primarily as a women’s health issue, but the data tells a different story. The American Urological Association estimates that male factor infertility is present in 50% of infertile couples. In about 20% of those couples, the problem lies entirely with the male partner, while in the remaining 30%, both partners have contributing factors.
Globally, the age-standardized prevalence rate for male infertility in 2021 was about 1,355 per 100,000 men of reproductive age. That translates to roughly 55 million men. Female infertility cases were about twice as high at 110 million, though this partly reflects differences in how infertility is diagnosed and recorded rather than a true biological gap.
Sperm Counts Are Declining
One of the most discussed findings in reproductive health over the past decade is a steady, global decline in sperm counts. A large meta-analysis found that sperm concentration dropped by about 0.75% per year across all populations studied. In Western countries (North America, Europe, Australia, and New Zealand), the decline was steeper: 1.4% per year in sperm concentration and 1.6% per year in total sperm count.
Between 1973 and 2011, total sperm count in Western men fell by 59.3%, dropping from an average of 337.5 million to 137.5 million per ejaculate. This isn’t just a Western phenomenon. Studies of Chinese, African, and Indian populations have found a similar trend of roughly 1% decline per year. The causes are still debated, but environmental chemicals, rising obesity rates, and lifestyle shifts are the leading suspects.
A declining average doesn’t mean every man is infertile, but it does mean more men are falling below the threshold where conception becomes difficult. The WHO considers a total sperm count below 39 million per ejaculate and a concentration below 16 million per milliliter to be below the normal reference range. As the population average drops, a growing share of men land in that zone.
The Most Severe Form: Zero Sperm Count
About 1% of all men and 10% of infertile men have azoospermia, a condition where no sperm appear in the ejaculate at all. This can result from a blockage preventing sperm from reaching the semen, or from the testes failing to produce sperm in the first place. Some causes are treatable (a blockage can sometimes be surgically corrected), while others require assisted reproduction techniques like extracting sperm directly from testicular tissue.
Varicoceles and Other Medical Causes
A varicocele, an enlargement of veins inside the scrotum, is the most common correctable cause of male infertility. About 15% of all men have one, and most never notice a problem. But among men with primary infertility (couples who have never achieved a pregnancy), varicoceles show up in 35% to 44% of cases. In men with secondary infertility (those who previously fathered a child but can no longer conceive), the rate climbs to 45% to 80%.
Varicoceles are thought to impair fertility by raising the temperature inside the scrotum, which damages sperm production over time. This helps explain why secondary infertility rates are higher: the damage accumulates. Surgical repair improves semen quality in many men, though it doesn’t guarantee pregnancy.
Other medical causes include hormonal imbalances, undescended testicles, genetic conditions, prior infections, and certain medications. In about 30% to 40% of cases, no identifiable cause is found, a category called unexplained male infertility.
Age Matters More Than Men Think
Unlike women, men continue producing sperm throughout life, which has created a persistent myth that male fertility doesn’t decline with age. It does. A 2020 study found that men over 40 are 30% less likely to achieve conception compared to men under 30. Sperm quality, including DNA integrity and motility, deteriorates gradually starting in the mid-30s. Older paternal age is also linked to higher rates of miscarriage and certain developmental conditions in offspring.
Smoking, Weight, and Other Lifestyle Factors
Smoking roughly doubles the rate of infertility in men compared to nonsmokers. It reduces sperm count, motility, and morphology while increasing DNA damage in sperm cells. The effects are dose-dependent, meaning heavier smokers see greater declines, but even moderate smoking has a measurable impact.
Obesity is another significant risk factor. Excess body fat disrupts hormone levels, particularly by converting testosterone to estrogen, which suppresses sperm production. Heat exposure from sedentary habits and excess tissue around the groin compounds the problem. Other lifestyle factors with documented effects on sperm quality include heavy alcohol use, anabolic steroid use, chronic stress, and exposure to industrial chemicals or pesticides.
The encouraging side of this is that many lifestyle-related causes are reversible. Sperm production takes about 74 days from start to finish, so men who quit smoking, lose weight, or reduce alcohol intake often see improvements in semen quality within two to three months.
How Male Infertility Is Identified
The first step is a semen analysis, which measures sperm count, motility (how well they swim), and morphology (their shape). The WHO’s current reference values set the lower limits of normal at 16 million sperm per milliliter, 39 million total per ejaculate, 42% progressive motility, and 4% normal morphology. Falling below these thresholds doesn’t mean conception is impossible, but it does mean the odds are reduced.
Because sperm quality fluctuates, a single abnormal result is usually followed by a repeat test a few weeks later. If results are consistently low, further evaluation may include hormone testing, genetic screening, or imaging to check for structural problems like varicoceles or blockages.