IDDM incidence in a multiracial population. The Hawaii IDDM Registry, 1980-1990

OBJECTIVE The Hawaii IDDM Registry was created to determine the incidence rate of IDDM among children aged < 15 years of Oahu between 1980 and 1990. Because of the multiracial population living in Hawaii, it is an ideal state in which to study the effect of migration on IDDM incidence. RESEARCH DESIGN AND METHODS Data were collected by a retrospective hospital chart review and physician survey. Registry criteria included 0–14 years of age at IDDM diagnosis and primary residence on Oahu. Children who were military dependents were excluded. Denominator data were compared from two sources. RESULTS A total of 113 new-onset IDDM cases were identified. Case ascertainment was 97%. The unadjusted annual incidence rate was 7.04–7.61 per 100,000 (95% CI 5.83–9.19), depending on which denominator source was used. Race- and ethnicity-specific rates varied greatly (all rates per 100,000): part Hawaiian, 15.34–16.58; Caucasian, 6.21–6.71; Filipino, 3.66–3.96; and Japanese, 2.85–3.08. Temporally, the incidence fluctuated between a low of 2.96 per 100,000 in 1981 to highs of 11.11 and 11.85 per 100,000 in 1985 and 1989, respectively. Ascertainment-corrected rates for these years (3.70, 11.76, and 13.48 per 100,000, respectively) show that the fourfold incidence increase between 1980 and 1989 was not due to ascertainment differences. CONCLUSIONS IDDM incidence among children < 15 years of age in Hawaii was the lowest documented in the U.S. The incidence among part-Hawaiian children was 2.5 times > that of Caucasian children in Hawaii. IDDM incidence rates among Japanese children in Hawaii were comparable with rates in Japan. The temporal variation in IDDM incidence corresponded with a mid-1980s pandemic of IDDM documented elsewhere.