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By Stephen M. Rao, PhD

Two recent scientific articles published in the journal Nature Genetics have shed light on the genetic causes of Alzheimer's disease. These two studies have received considerable attention in the general media because of the sheer scope of the projects. Scientists from the United States and Europe conducted genetic testing on over 50 thousand people, approximately half of whom were diagnosed with Alzheimer's disease and the other half were persons of similar age who have not shown any evidence of cognitive decline.

Prior to the publication of these two articles, five genes were shown to occur more frequently in patients with Alzheimer's disease than in healthy persons. The new studies expand the number of genes from 5 to 10. These 10 genes appear to be involved in the production of cholesterol and in the brain's response to inflammation. Previous clinical studies have noted that persons with elevated cholesterol levels are more prone to being diagnosed with Alzheimer's disease. In addition, persons who have experienced inflammation to their brain, either as the result of stroke or head injury, are more likely to develop Alzheimer's disease later in life.

Findings from these two genetic studies may provide vital clues as to the possible underlying brain pathology that produces Alzheimer's disease. The fact that the genes are linked to inflammation and cholesterol production may one day result in novel treatments or vaccines for slowing down the disease or preventing it all together.

One cautionary note: it is unlikely that the results from these studies will result in a clinical test for diagnosing Alzheimer's disease prior to the onset of symptoms. The best genetic predictor - having one or both apolipoprotein (APOE) e-4 genes - increases the chances of getting Alzheimer's disease by 4 to 10 times the general population. The remaining 9 genes provide even less precise information. As a result, genetic profiles are simply not accurate for making a diagnosis of Alzheimer's disease.

To summarize, scientists are excited because these large scale genetic studies may open up new areas of investigation for understanding the causes of Alzheimer's disease. Once the causes are more precisely known, there is considerable optimism that novel therapies can be designed to eradicate Alzheimer's disease. In a disease that currently affects 5.4 million Americans and is projected to involve 15 million by 2050, such treatments are crucially needed for patients and their family members, not to mention to allay the strain on our health care delivery system.

Stephen M. Rao, PhD, ABPP-Cn, is the Ralph and Luci Schey Chair and Director of the Schey Center for Cognitive Neuroimaging at Cleveland Clinic.

Published April 12, 2011

See Also:

• Understanding Alzheimer's Disease
• Dementia vs. Alzheimer's: What's the Difference?
• 9 Tips for Alzheimer's Caregivers