ArticlesDifference in prevalence of congenital cryptorchidism in infants between two Nordic countries
Introduction
In several reports, investigators have described adverse trends in male reproductive health, including high and increasing prevalence of testicular cancer and low and possibly declining semen quality.1, 2, 3, 4, 5 Reports on semen quality and testicular cancer have shown notable differences between Denmark and Finland, Denmark having poorer male reproductive health.1, 6 Highly variable prevalence rates of cryptorchidism have been reported in Western countries on the basis of registry studies.7, 8 Cryptorchidism is often, inappropriately, judged to be a minor malformation. Official records of registration might therefore be unreliable, rendering registry-based studies insufficient for assessment of geographical and temporal trends.9 Thus, we undertook a synchronised and standardised cohort study to investigate the prevalence of congenital cryptorchidism in Denmark and Finland.
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Study design
The prospective cohort study was done at the University Hospital of Copenhagen (Rigshospitalet and Hvidovre Hospital) in Denmark during 1997–2001 and the Turku University Central Hospital in Finland in 1997–99. Researchers from both countries closely collaborated in study design. Recruitment and examinations were completely standardised. To keep interobserver variation to a minimum, bi-national workshops were held regularly and borderline cases were examined by two researchers from the national
Results
At the expected date of delivery, 9·0% (95% CI 7·3–10·9) of the Danish boys and 2·4% (1·7–3·3%) of the Finnish boys had either unilaterally or bilaterally undescended testes (figure). In nine premature boys from the total Finnish hospital cohort, testes descended spontaneously between birth and the expected date of delivery, whereas 2·1% (1·7–2·5%) were still cryptorchid at the expected date of delivery. At 3 months of age, the rate had fallen to 1·9% (1·2–3·0%) in the Danish cohort and to 1·0%
Discussion
In this standardised study, done simultaneously at two University Hospitals in Copenhagen, Denmark, and Turku, Finland, we documented a striking difference in the prevalence of congenital cryptorchidism between two Nordic countries. The Danish birth prevalence of the condition, especially for mild forms, was four-fold higher than that of Finland. This finding corresponds to reports about other aspects of male reproductive health, which show a high and increasing incidence of testicular cancer
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