Elsevier

The Lancet

Volume 363, Issue 9417, 17 April 2004, Pages 1264-1269
The Lancet

Articles
Difference in prevalence of congenital cryptorchidism in infants between two Nordic countries

https://doi.org/10.1016/S0140-6736(04)15998-9Get rights and content

Summary

Background

Several investigators have shown striking differences in semen quality and testicular cancer rate between Denmark and Finland. Since maldescent of the testis is a shared risk factor for these conditions we undertook a joint prospective study for the prevalence of congenital cryptorchidism.

Methods

1068 Danish (1997–2001) and 1494 Finnish boys (1997–99) were consecutively recruited prenatally. We also established prevalence data for all newborns at Turku University Central Hospital, Finland (1997–99, n=5798). Testicular position was assessed by a standardised technique. All subtypes of congenital cryptorchidism were included, but retractile testes were considered normal.

Findings

Prevalence of cryptorchidism at birth was 9·0% (95% CI 7·3–10·8) in Denmark and 2·4% (1·7–3·3) in Finland. At 3 months of age, prevalence rates were 1·9% (1·2–3·0) and 1·0% (0·5–1·7), respectively. Significant geographic differences were still present after adjustment for confounding factors (birthweight, gestational age, being small for gestational age, maternal age, parity, mode of delivery); odds ratio (Denmark vs Finland) was 4·4 (2·9–6·7, p<0·0001) at birth and 2·2 (1·0–4·5, p=0·039) at three months. The rate in Denmark was significantly higher than that reported 40 years ago.

Interpretation

Our findings of increasing and much higher prevalence of congenital cryptorchidism in Denmark than in Finland contribute evidence to the pattern of high frequency of reproductive problems such as testicular cancer and impaired semen quality in Danish men. Although genetic factors could account for the geographic difference, the increase in reproductive health problems in Denmark is more likely explained by environmental factors, including endocrine disrupters and lifestyle.

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.

Section snippets

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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