Biomarkers can predict risk for Alzheimer’s several years before symptoms appear

Brain imaging and spinal-fluid testing can help predict which cognitively normal older people will develop Alzheimer’s disease as many as 7.5 years before symptoms appear, according to a new study supported in part by the NIA. The findings confirm the power of biomarkers as predictors of disease risk in the earliest, symptom-free stages of Alzheimer’s disease. These biomarkers may prove to be valuable tools in testing promising treatments in future studies. While not typically used in clinical practice, investigators worldwide are studying, refining, and standardizing biomarkers aimed at identifying who is at risk for developing Alzheimer’s, the most common form of dementia in older adults. The biomarkers in this study, published May 7 in Neurology, included positron emission tomography (PET) scans of the brain to detect deposits of the telltale protein beta-amyloid, as well as levels of beta-amyloid and another protein, tau, found in cerebrospinal fluid. The research team, at Washington University School of Medicine in St. Louis, tracked the cognition of 201 dementia-free volunteers, ages 45 to 88, at the school’s Alzheimer’s Disease Research Center.
The researchers found that abnormal levels of biomarkers identified in PET scans and lumbar punctures could predict who would develop cognitive impairment among the volunteers who were followed for an average of 3.7 years, but in some cases as long as 7.5 years. Some 28 volunteers (14 percent) of the group developed memory loss and other signs of cognitive impairment. Abnormal levels of all biomarkers predicted the development of Alzheimer’s dementia equally well, the study found. Older participants, men, and African Americans who developed dementia did so faster than those who were younger, female, and white, the researchers report. In a few cases, participants with abnormal biomarker levels remained cognitively normal, perhaps because of “cognitive reserve,” the ability of some brains to cope with or stave off decline.
Reference: Roe CM, et al. Amyloid imaging and CSF biomarkers in predicting cognitive impairment up to 7.5 years later.

Reference: Roe CM, et al. Amyloid imaging and CSF biomarkers in predicting cognitive impairment up to 7.5 years later. Neurology 2013;80(19):1784-91.