Science / Medicine : Single Alzheimer’s Cause Doubted

Dashing hopes that one genetic flaw might hold the answer to Alzheimer’s disease, a landmark study published last week in Nature showed that the mystifying brain disorder apparently has multiple causes, as do heart disease and cancer. A single cause might have made it easier to find ways to prevent and treat the devastating disease that afflicts as many as 4 million Americans. Alzheimer’s disease is a gradual, irreversible erosion of brain cells that control thought and memory.

Recent research had indicated that a defective gene on chromosome 21 may be the primary cause of Alzheimer’s disease, especially in the minority of patients stricken before age 65. But other scientists had argued that Alzheimer’s is not a single disease, but an array of disorders produced by a variety of factors that cause similar symptoms.

An international team of more than 65 leading scientists analyzed genetic material from patients from 48 families with a history of Alzheimer’s to look for signs of genetic defects in the suspect region of chromosome 21. Although some patients with early onset Alzheimer’s had flaws on chromosome 21, most patients had none--suggesting their disease was caused by different genetic factors, environmental influences or possibly both.