Stanford University researchers say they may have found a key that causes people with Down syndrome to develop early Alzheimer's disease.

The findings, published in Thursday's edition of the journal Neuron, are said to offer a lengthened target for drug research and hope for treatment because people with Down syndrome are living longer than before.

Scientists say Down syndrome affects about 350,000 Americans, causing mental retardation and a risk of premature Alzheimer's dementia, The Wall Street Journal reports.

Stanford's Ahmad Salehi, Jean-Dominique Delacroix and William C. Mobley, lead authors of the study, zeroed in on a gene known as App (for amyloid precursor protein), already a known culprit in other forms of Alzheimer's.

Copyright 2006 by United Press International