engleski

A high rate of Down's syndrome in two regions of Croatia

In the light of concern about possible environmental influences on Down's syndrome incidence, we would like to bring to attention a high rate of Down's syndrome in Croatia. Since 1983, the Zagreb EUROCAT registry of congenital anomalies has been operating in Croatia, covering geographically defined populations in the cities of Rijeka and Varaždin since 1983 (5% of births in Croatia) and extending to the region of Varaždin and Istria since 1986 (bringing coverage up to 9% of births in Croatia). Comparison of rates of Down's syndrome with other EUROCAT registries, and an analysis over time, showed an unusually high rate of Down's syndrome. This was first noticed in 1987 for data up to 1986, and has continued in subsequent surveillance to 1988. More recent data are not yet available. As induced abortions following prenatal diagnosis, which we do not register among cases in Croatia, complicate comparisons for older mothers, we restricted further analysis to younger mothers (less than 30 years of age) and liveborn cases. We calculated the expected number of cases using the average EUROCAT rates for the age groups <20, 20-24 and 25-29 applied to the maternal age distribution of the study population for each year. There were twice as many cases observed than expected (O/E=2.1, 95% CI 1.5-2.9). This increase seems to be particularly strong in the time period 1986- 1988, and perhaps for the extension of the registration region. All cases have been verified with respect to maternal residence and karyotype. Only one diagnosis had no karyotype confirmation. We do not believe this increase to be related to Chernobyl, not only because the irradiation of the Croatian population would be unlikely to cause a detectable increase in Down's syndrome, but also because all of the cases in 1986 were conceived before the accident, and thus the phenomenon seems to predate Chernobyl. Investigation continues, but we would be most interested to hear of other investigations of Down's syndrome clusters.

down syndrome ; Croatia ; high rate

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