Men without children have a lower risk of prostate cancer than fathers, but those who father a brood of children appear to have a relatively low risk also, a study suggests.
Lead author Kristian Jorgensen, of the Statens Serum Institut in Copenhagen, and colleagues followed all men bornin Denmark between 1935 and 1988. Researchers found that compared with fathers, childless men were 16 per cent less likely to develop prostate cancer.
Among fathers, though, the risk of the disease gradually declined as the number of children in the family increased, the researchers report in the medical journal Cancer.
The reasons for the seemingly contradictory links cannot be determined from the study data, say the researchers. However, they note, the results build on those from past studies linking childlessness to a lower risk of prostate cancer.
One theory is that men who are childless due to fertility problems may have a lower prostate cancer risk because of lower testosterone levels. This has yet to be proven, Jorgensen's team notes.
Childless men in this study had a variety of possible reasons, say the researchers - some were infertile, some had an infertile partner and some had chosen not to have children.
Why men with several children had a lower prostate cancer risk than those with one or two children may potentially be explained by the "healthy father" phenomenon, the researchers speculate. That is, men with a large number of children may retain their fertility to a relatively late age and may be more resistant to developing prostate cancer.
More studies will be needed to understand the "biologic, environmental, social and/or behavioral factors" that underlie these findings, the researchers conclude.
