To determine the incidence of type I diabetes among individuals <30 years of age on the island of Barbados in the Caribbean. The population is predominantly African in origin but exhibits a relatively westernized lifestyle.
Cases occurring during the years 1982–1991 were drawn from records at Queen Elizabeth Hospital and from physicians treating insulin-dependent diabetes mellitus (IDDM) patients. Patients using insulin and <30 years of age at onset were included. Ascertainment was estimated at 94%.
The average annual incidence of type I diabetes among Barbadians was 4.1/100,000 when age-adjusted to the world's population. There were 59 incident cases during this 10-year interval. The risk for males was 4.4 and for females 4.0/100,000. Among those 0–14 years of age, the risk was 5.0/100,000. Mean age at onset (± SD) was 14.7 ± 6.9 for males and 12.5 ± 5.7 for females. Males showed marked seasonal variation in risk and a more than threefold increase in annual incidence during 1984–1985. In contrast, females exhibited a stable pattern of IDDM risk during the 10-year interval.
The incidence rate in Barbados falls near the lower limits of rates reported for Caribbean populations. There was a marked seasonal effect among males, even though the climate varies little throughout the year. This observation, and the incidence peak during 1984–1985, provide support for the role of environmental factors in the etiology of IDDM.