Diabetes and MS linked in Danish study

People with type 1 diabetes are more than three times more likely to develop multiple sclerosis (MS) than are those without diabetes, new research from Denmark shows.

In addition, the two diseases appear to be linked, albeit to a weaker extent, within families.

Both type 1 diabetes and MS are auto-immune diseases, in which the body mounts an aberrant immune response against its own tissues -- attacking insulin-producing cells in the case of diabetes, and the myelin sheath surrounding neurons in MS.

The new, population-based study is not the first to reveal an association between type 1 diabetes and MS. However, previous evidence had come from relatively small numbers of patients.

As reported in the Archives of Neurology, Dr. Nete M. Nielsen, from the Statens Serum Institut in Copenhagen, and colleagues assessed the occurrence of MS in 6078 patients with type 1 diabetes over more than a decade of follow-up.

In addition, the researchers evaluated the presence of type 1 diabetes in 14,771 first-degree relatives of 11,862 MS patients.

Eleven cases of MS developed in the diabetes patients, while only 3.38 cases would be expected based on the rates in the general population. Thus, patients with type 1 diabetes had a more than three-fold increased risk of MS.

First-degree relatives of MS patients had a 63 percent increased risk of developing type 1 diabetes, the team calculated from their data. However, after accounting for the possibility of also being related to a patient with type 1 diabetes, the excess risk fell to 44 percent.

"To our knowledge, the present study is the first truly nationwide cohort study to demonstrate intraindividual and, to a lesser degree, intrafamilial co-occurrence of MS and type 1 diabetes," the investigators write.

"The underlying mechanisms remain unknown," they say, "but may involve both genetic and environmental factors."

SOURCE: Archives of Neurology, July 2006