Incidence of insulin-dependent diabetes mellitus among Sardinian-heritage children born in Lazio region, Italy.

BACKGROUND: The relative importance of genetic and environmental factors in causing insulin-dependent diabetes mellitus (IDDM) is unknown. We studied this question by assessing the incidence of the disease in children, born in a region with a low incidence of IDDM (Lazio), but whose parents came from a region with high incidence (Sardinia). METHODS: We identified all IDDM cases that occurred between 1989 and 1994. We used as the denominator the number of children aged 0-14 born in Lazio of Sardinian parents to calculate incidence. We compared this rate with the incidences of IDDM in the populations of Lazio and Sardinia. FINDINGS: The age-adjusted incidence of IDDM in Sardinian-heritage children born and living in Lazio was 33.8 per 100,000 per year (95% CI 7.0-99.0) for those with two Sardinian parents, and 15.9 (8.7-26.6) for those with only one parent from Sardinia. The former incidence was not different from that recorded in Sardinia (34.4, 31.3-37.9), but was fourtold that of Lazio-heritage children (7.9, 7.1-8.8). INTERPRETATION: Our results show that two different ethnic groups living in the same region have a fourfold difference in incidence of IDDM. Children of Sardinian-heritage born in Lazio have the same incidence as the population of origin, which is genetically prone to the disease. Moreover, children with one Sardinian parent had a rate half that of Sardinians and double that of the indigenous population. We conclude that in a given population genetic susceptibility determines the frequency of IDDM in response to the environmental challenge.

A 5-year (1989-1993) prospective study of the incidence of IDDM in Rome and the Lazio region in the age-group 0-14 years.

OBJECTIVE: To provide data on the incidence of IDDM in Rome and the Lazio region evaluated prospectively from 1989 to 1993 for a total of > 5 million subjects younger than 15 years. RESEARCH DESIGN AND METHODS: All patients with newly discovered IDDM diagnosed between 1 January 1989 and 31 December 1993 among residents in Rome and its region were recorded. Primary ascertainment was based in diabetes clinics and specialized hospitals in the region, whereas the secondary independent source was taken from the archives of the region where patients are registered to obtain exemption from paying for medications. RESULTS: We identified 330 new patients with a degree of ascertainment of 85%. Overall the incidence rate of the disease was 7.9 per 100,000 per year (95% CI 7.1-8.8). The incidence was higher in the 5- to 9-year-old age-group (10.4 per 100,000) and in winter (36.2%). The cumulative risk for the disease is on the order of 1.18 per 1,000 subjects < 15 years of age. No significant differences in incidence were observed between boys and girls. There were 14 instances of coma at diagnosis (4.3%), but hyperglycemia without ketonuria was diagnosed in 35% of patients, suggesting an early diagnosis. DISCUSSION: Compared with the other continental Italian regions for which data are available for a single year, the IDDM incidence rate in Rome is similar. We conclude that the IDDM incidence rate in Rome and its region is comparable to that in other Southern European countries and remained stable over the 5-year observation period.