Diabetes Mystery: Why are Type 1 Cases Surging?

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When public health officials fret about the soaring incidence of diabetes in the U.S. and worldwide, they are generally referring to type 2 diabetes. About 90 percent of the nearly 350 million people around the world who have diabetes suffer from the type 2 form of the illness, which mostly starts causing problems in the 40s and 50s and is tied to the stress that extra pounds place on the body?s ability to regulate blood glucose. About 25 million people in the U.S. have type 2 diabetes, and another million have type 1 diabetes, which typically strikes in childhood and can be controlled only with daily doses of insulin.

For reasons that are completely mysterious, however, the incidence of type 1 diabetes has been increasing throughout the globe at rates that range from 3 to 5 percent a year. Although the second trend is less well publicized, it is still deeply troubling, because this form of the illness has the potential to disable or kill people so much earlier in their lives.

No one knows exactly why type 1 diabetes is rising. Solving that mystery?and, if possible, reducing or reversing the trend?has become an urgent problem for public health researchers everywhere. So far they feel they have only one solid clue.

?Increases such as the ones that have been reported cannot be explained by a change in genes in such a short period,? says Giu?seppina Imperatore, who leads a team of epidemiologists in the Division of Diabetes Translation at the U.S. Centers for Disease Control and Prevention. ?So environmental factors are probably major players in this increase.?

A Challenge of Counting
Type 1 and type 2 diabetes share the same underlying defect?an inability to deploy insulin in a manner that keeps blood sugar from rising too high?but they arise out of almost opposite processes. Type 1, which once was known as juvenile diabetes, is an autoimmune disease in which the body attacks its own cells?namely, the beta cells of the pancreas?destroying their ability to make insulin. In type 2, formerly known as adult-onset diabetes, tissues that need insulin to take up glucose (such as the liver, muscles and fat) become resistant to insulin?s presence. The insulin-producing cells respond by going into overdrive, first making more of the hormone than normal and then losing the ability to keep up with the excess glucose in the blood. Some people end up unable to make insulin at all.

The first strong signal that the incidence of type 1 diabetes was on the rise came in 2006, from a World Health Organization project known as DIAMOND (a combination of words in several languages for worldwide diabetes). That survey, which looked at 10 years of records from 112 diabetes research centers in 57 countries, found that type 1 had risen an average of 5.3 percent a year in North America, 4 percent in Asia and 3.2 percent in Europe.

Statistics from Europe?where the single-payer health care systems that care for residents throughout their lives generate rich stores of data?back up that first finding. In 2009 researchers from a second project called EURODIAB compared diabetes incidence across 17 countries and found not only that type 1 was rising?by 3.9 percent a year on average?but also that it was increasing most quickly among children younger than five. By 2020, they predicted, new cases of type 1 diabetes in that age group will nearly double, from 3,600 children to an estimated 7,076 children.

Most assessments of diabetes in the U.S. have been more partial and local. There is one comprehensive national surveillance project, the federally funded SEARCH for Diabetes in Youth study, which published data in 2007. Because that was an initial report, however, researchers could not compare it with earlier years. Still, when looked at against the findings of other studies, it suggests a rising tide. For example, the 2007 study found higher rates of type 1 in the U.S. than did the WHO?s worldwide study of the year before. In addition, the SEARCH study results were sharply higher than regional studies from the 1990s in Alabama, Colorado and Pennsylvania.

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