Incidence trends in childhood onset IDDM in four countries around the Baltic sea during 1983-1992

Abstract

Incidence of childhood insulin-dependent diabetes mellitus (IDDM) is rising in many areas of the world [1,2]. Despite the role of HLA genetics in the aetiology of IDDM being well known [3,4] the role of putative environmental factors is not yet understood [5][6][7]. Epidemiologically based standardized surveillance systems provide information on the pattern of IDDM incidence which make comparison of IDDM incidence between countries within close geographical areas possible, thus offering an "indirect" way to trace potential environmental factors in the aetiology of IDDM. A collaborative study on the childhood IDDM incidence in countries around the Baltic Sea was started in 1989 named "DIABALT". Short-term data have demonstrated a wide variation in the incidence of IDDM between countries around the Baltic Sea [8,9], from the highest incidence in the world in Finland to one of the lowest within Europe in Poland. In order to obtain more standardized rates for comparison of secular trends in incidence of IDDM in Finland, Estonia, Latvia and Lithuania the analyses of the data were carried out for the period 1983 to 1992. Subjects and methodsGeographically the Baltic States of Estonia, Latvia and Lithuania are located on the south-east coast, while Finland is on the northern coast of the Baltic Sea. Genetically and culturally, the population of Finland is homogeneous [10], while Estonia Diabetologia (1997) 40: 187-192 Incidence trends in childhood onset IDDM in four countries around the Baltic sea during 1983-1992 Summary We present secular trends of childhood onset insulin-dependent diabetes mellitus (IDDM) in Finland, Estonia, Latvia and Lithuania during the period of [1983][1984][1985][1986][1987][1988][1989][1990][1991][1992]. Incidence data were obtained from the national IDDM registries. The average agestandardized incidence per 100 000/year was 35.0 in Finland, followed by 10.2 in Estonia, 7.1 in Lithuania and 6.5 in Latvia. A male excess in incidence was recorded in Finland (1.15) and Latvia (1.01). In all countries, the highest age-specific risk of IDDM was observed in the 11-13 year age range. The large difference in incidence between Finland and other Baltic countries was seen even in 1-2-year-old children. During the 10-year study period overall changes in incidence of IDDM were relatively small in these four countries. The incidence increased in Finland and Lithuania on average by 1 % and 1.4 % per year, respectively. A statistically significant increase was recorded only in 0-4 year old children in Finland, at 5.6 % per year. In Estonia, an 8.3 % increase in this age group, however, was not statistically significant. The different trends in the age-group specific incidence rates were confirmed in Finland. In conclusion, from 1983 to 1992 the incidence of childhood onset IDDM was increasing in Finland and Lithuania, while in Latvia and Estonia it was stable. There are still great differences in IDDM incidence between the countries around the

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