Lead author Dr. Michael Eisenberg, assistant professor of urology at the medical school and director of male reproductive medicine and surgery at Stanford University School of Medicine, and colleagues said diagnoses of male infertility and azoospermia are surprisingly common in the United States.
About 4 million U.S. men -- 15 percent of those ages 15-45 -- are infertile, of which some 600,000 are azoospermic, the study said.
Eisenberg conducted most of the analysis at Stanford using data gathered from the Texas Cancer Registry and the Baylor College of Medicine in Houston, where he completed his medical training.
The study involved 2,238 infertile men who were seen at a Baylor andrology clinic from 1989-2009. Their median age was 35.7 when they were first evaluated for the cause of their infertility.
Of those men, 451 had azoospermia, and 1,787 did not. There were no further apparent initial differences between the two groups.
The study, published in the journal Fertility and Sterility, found a diagnosis of azoospermia before age 30 carried an eight-fold cancer risk.
"An azoospermic man's risk for developing cancer is similar to that for a typical man 10 years older," Eisenberg, said in a statement. "There is evidence that infertility may be a barometer for men's overall health, and a few studies have found an association of male infertility with testicular cancer."
The study not only assigns the bulk of infertile men's increased cancer risk to those with azoospermia, but also suggested this risk extends beyond testicular cancer, Eisenberg said.