Alzheimer's disease, the neurological disorder that affects some 5 million Americans, may in some cases be preceded by an ailment called mild cognitive impairment. But some researchers are skeptical that MCI, marked by the progressive loss of memory, is even a real disorder.

"MCI is an arbitrary category on the continuum of cognitive aging," said Dr. Peter Whitehouse of Case Western Reserve University in Cleveland.

Whitehouse cautions that many misunderstood phenomena have been mistakenly labeled as illnesses. "Remember, homosexuality and hysteria used to be diseases -- and do not forget 'drapetomania,' the pre-Civil War disease that caused slaves to run away."

No Test Available for MCI

Criticism of the term MCI has become louder following the publication of a recent study involving Aricept, a drug used to treat the symptoms of Alzheimer's disease.

The research, published in the New England Journal of Medicine, showed that Aricept slows the onset of Alzheimer's disease. Researchers believe Aricept, given to patients showing the symptoms of MCI, pushes back the diagnosis of Alzheimer's disease by a year.

There is no test currently available that can make a definitive diagnosis of MCI. Only detailed patient histories, along with specific cognitive and psychological testing, can help physicians make a diagnosis of MCI.

Disagreement regarding the term MCI relates to its broad usage. Some feel that the term is too inclusive and may capture persons who just have a normal mental decline associated with aging.

Is MCI a Marketing Tool?

Other experts suggest there may be an ulterior motive behind creating an MCI, or "early Alzheimer's," diagnosis.

"MCI is a marketing tool for drug companies," said Dr. Thomas Finucane, professor of geriatric medicine at Johns Hopkins University in Baltimore.

"They are taking advantage of the despair and heartbreak of caregivers who love family members with Alzheimer's, and selling billions of dollars worth of drugs that have no meaningful effect," Finucane said.

Despite the controversy, the Aricept study and the description of MCI are largely welcome, given the encouraging results of delaying Alzheimer's for a year.

"Saying all people with MCI in all studies around the world should be treated is incorrect," said study author Dr. Rachelle Doody, professor of neurology at Baylor College of Medicine in Houston. "What we did in this study was define a subtype of MCI -- the ones that are to become Alzheimer's patients."

Other researchers believe MCI is unquestionably a valid diagnosis.

"This is a real condition," said Dr. D.P. Devanand, research scientist at Columbia University in New York.

"In MCI the rate of conversion to Alzheimer's disease is around 10 [percent] to 15 percent annually compared to 1 [percent] to 2 percent in healthy elderly comparison subjects," Devanand said. "This difference validates the concept of MCI."