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Epidemiology
Incidence and Prevalence
Type 1 accounts for 10% of all types of diabetes. Prevalence of Type 1 is estimated to be between 700,000 to 800,000 individuals. The annual incidence of Type 1 is estimated at 30,000 cases per year in the United States (US). Worldwide incidence rates vary from 1.7/100,000 in Japan to 29.5/100,000 in Finland. The incidence of Type 1 is on the increase. (4,13,14)
Age
Diagnosis is most commonly made in individuals between the ages of 5-20. Generally, onset of Type 1 occurs under the age of 30 but can happen at any age. Peak incidence of Type 1 is at puberty. This age pattern is consistent across world populations. Age-related factors may include growth spurts, hormonal changes and exposure to infectious agents. (12,16)
Gender
Gender does not seem to be a factor in the incidence of Type 1. (8)
Geographic Distribution
Finland, Sweden and Sardinia, Italy have the highest incidence rate of Type 1. Countries with intermediate rates of Type 1 include Caucasians in the US, New Zealand and Spain. The lowest rates of Type 1 incidence occur in Mexico, Chile and Japan. Incidence rates vary within countries and may increase in areas with colder climates. (8,15)
Race/Ethnicity
The incidence of Type 1 is greater among Caucasians than African Americans, Hispanics, Asians and Native Americans. (8)
Familial Factors
Caucasians, native to North America, who are first-degree relatives to a diagnosed Type 1 diabetic are 1 to 15% more likely to have Type 1 themselves.
The American Diabetes Association assesses the risk of developing Type 1 to be between 10%-25% if both parents have Type 1. If the father has Type 1 the child is at a 4% risk. Depending upon the mother's age at onset (less than or greater than 25 years) the child's risk is between 1%-4%. More than 80% of cases occur in persons without a family history of diabetes. The remaining 20% have a familial link to diabetes. (8,12,15)
Other Risk Factors
Several other factors that may promote onset of Type 1 include, but are not limited to; (a) diet (decreased length of breast feeding, early introduction of cow's milk, malnutrition), (b)exposure to certain viruses such as coxsakie B4 or congenital rubella.
It is clear that the onset of Type 1 is multifactoral. These factors may differ among racial/ethnic groups and there may be many more, yet undiscovered causative agents of Type 1. (8,15)
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