A study of medical claims data by Surveillance Data Inc. shows that patients treated with intravenous immunoglobulin, marketed as Gammagard by Baxter International, were less likely to develop Alzheimer's and related disorders, the Chicago Tribune said Thursday.

The report looked at 847 patients who were treated with Gammagard and 84,700 who were not. Dementia was diagnosed in 2 percent of treated cases, compared with 4.2 percent for the untreated control group.

The newspaper said researchers are looking at the possibility that Gammagard can clear the brain of a protein fragment known as beta-amyloid that is thought to be a key in the development and progression of Alzheimer's.