Researchers at Lund University analysed national registry data on 1,137,829 Swedish men who had their first child between 1994 and 2014, linking fatherhood records to the national cancer registry. The cohort included 14,540 men who became fathers through ICSI, a treatment used in cases of severe male infertility, 20,142 who conceived through standard IVF, and over 1.1 million who conceived naturally, making it one of the largest investigations of its kind.
Compared with men who conceived naturally, fathers via ICSI had roughly twice the risk of colorectal cancer and three times the risk of thyroid cancer, the team reports in the European Journal of Epidemiology. The researchers, including Lund University docent Angel Elenkov, emphasise that the fertility treatment itself does not cause cancer, and that absolute risks remain low in this age group. Rather, severely reduced fertility appears to act as a biological marker that flags broader vulnerabilities in a man's health.
The finding fits a growing body of work linking low male fertility to diabetes, cardiovascular disease and shorter life expectancy. Men investigated for infertility are typically in their early thirties and currently receive no follow-up on their general health, a missed opportunity given that colorectal and thyroid cancers are rising among younger adults. The team now plans to work with Scandinavian clinics and the Swedish-Danish RUBIC biobank to identify which subgroups would benefit most from preventive health checks.