Male infertility and prostate cancer are common diseases in men, both occurring in about 8-10% of the male population. Many of us have wondered whether there is any relationship between the two conditions and specifically whether fatherhood status alters prostate cancer risk. Does having lots of kids “protect” men from getting prostate cancer? Likewise, does having male infertility increase the risk of prostate cancer? In our unending fight against cancer, it would be great to know if male infertility is a “marker” of later prostate cancer to help us either diagnose cancers earlier or prevent them entirely. Admirable men’s health goals, by any measure.
Research linking male infertility and prostate cancer began in earnest 15 years ago. European studies that used the number of children sired as a marker of male infertility produced mixed results. We thought this might be the case because fatherhood is…well…complicated. To be more specific, it takes two to tango — the lack of fatherhood involves two partners, not just the male. We felt that a better measure of male infertility is the semen analysis because that’s how we actually diagnose infertility. So, we published a large-scale U.S. based study (involving 22,562 men) that examined the development of prostate cancer among men specifically found to have male factor infertility earlier in life. Lo and behold, we found that, when compared to fertile men:
- Infertile men with low or no sperm counts have an almost threefold higher risk of developing high-grade (i.e., important) prostate cancer later in life and
- Infertile men with normal sperm counts (i.e. non-male-factor infertility) have no increased risk of developing high-grade prostate cancer.
Our findings were concerning to be sure, but really needed validation by more studies to be considered actionable “fact” in medicine. And that validation just arrived.
The Land of Ikea
You gotta love Sweden, the home of Volvo, Saab and Ikea. The Swedes track everything about the health of their population in national registries. They just published a very large study (involving 1,181,490 men) that examined prostate cancer rates in “virtually all men fathering a child in Sweden [over the last] two decades.” Importantly, the measure used to define male infertility wasn’t the number of babies fathered but the need for couples to use assisted reproduction (IVF, IVF-ICSI) to conceive. Since ICSI in Sweden (very unlike the U.S) is only used for male factor infertility (low or no sperm counts), ICSI is a reasonable surrogate for the criteria of abnormal sperm counts that we used in our study. And with this measure, they found a 64% increase in prostate cancer rates in men who had conceived with ICSI compared to men who conceived naturally. Same ballpark risk as in our study but garnered from a much larger cohort and from a different continent.
It takes time, often decades, for scientific observations to be deemed medical “fact.” The increased risk of prostate cancer among infertile men just got a giant step closer to becoming clinical truth in my eyes.