The study was small and doesn't prove that type 1 diabetes causes male infertility. But the findings deserve further research, write the researchers, who are based in Belfast, Northern Ireland.
They included Ishola Agbaje, MD, of the Reproductive Medicine Research Group at Queen's University of Belfast.
Agbaje and colleagues studied semen and blood samples from 27 men with type 1 diabetes. Those men weren't necessarily infertile; they were invited to participate in the study while getting routine diabetes checkups.
Both groups of men were in their early to mid-30s, on average.
Sperm Study's Findings
The men with diabetes had lower semen volume than the men without diabetes. But the diabetes patients' semen volume was still within the normal range set by the World Health Organization (WHO).
Sperm count, shape, and motion (motility) were similar in both groups of men.
But when the researchers analyzed the sperms' DNA, they found more DNA damage in the diabetes patients' sperm. Sperm damage may increase infertility, note the researchers.
Many factors can cause DNA damage. It's not clear whether diabetes was responsible for the DNA damage seen in the study.
The study didn't include any men without diabetes who weren't undergoing infertility tests. Such men might have even less DNA damage in their sperm than the study groups, the researchers note.
Agbaje's team calls for further studies on DNA sperm damage -- and its possible fertility consequences -- in men with type 1 diabetes.
The study appears online in the journal Human Reproduction.