NEW YORK (Reuters Health) - The city of Philadelphia experienced a jump in type 1 diabetes in children in 1993, roughly 2 years after a measles epidemic hit the area, according to a new report.

The link between measles and type 1 diabetes is not proven, although the researchers suggest that some children may have developed diabetes after coming down with the measles.

In an interview with Reuters Health, Dr. Terri H. Lipman, of the University of Pennsylvania in Philadelphia, said that it is "very important" to note that the study does not prove that the measles cases were to blame for the jump in diabetes cases. In some studies, measles have been shown to trigger an autoimmune reaction similar to what occurs in type 1 diabetes, but other studies have not shown this effect.

"Nothing has been proven," she said. "The evidence is not clear."

Type 1 diabetes is sometimes called juvenile diabetes because it usually strikes at a younger age than the more common type 2 diabetes. In type 1 diabetes, the immune system launches a misguided attack against insulin-producing cells and patients must take daily insulin injections.

Though diet and lifestyle play a major role in type 2 diabetes, which is on the rise, the factors that affect a person's chances of developing type 1 diabetes are less certain.

In a report in the November issue of the journal Diabetes Care, Lipman's team summarizes the new cases of type 1 diabetes that occurred in children in Philadelphia from 1990 to 1994. During that time, 209 Philadelphia children were diagnosed with type 1 diabetes.

The "most interesting finding," the researchers note, is a jump in type 1 diabetes cases that occurred in 1993. There were 32 new cases of type 1 diabetes reported between January and June in 1993, compared with 12 cases in the first 6 months of 1992, and 18 cases in that time period in 1991.

In a review of Philadelphia health records, the researchers discovered that the city experienced a measles outbreak in late 1990 through the first half of 1991.

Lipman and her colleagues point out that several factors have been associated with changes in the rate of new cases of type 1 diabetes, including viruses, vaccinations and infants' diets. But the authors note that determining exact causes is difficult. For example, it is hard to know how much time lags between exposure to a possible risk factor and development of diabetes.

"The important thing," according to Lipman, "is that we need to have very careful ways to look at diabetes incidence." The formation of more diabetes registries like the one in the study would go a long way in helping researchers understand the causes of diabetes, she said.

Lipman also said, "The public should know that the incidence of diabetes is definitely increasing in black children." That more and more African-American children are developing type 2 diabetes, the form of the disease that is often related to obesity, has been known, but this study provides additional evidence that there is also a rise in type 1 diabetes, Lipman said.

SOURCE: Diabetes Care 2002;25:1969-1975.