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Most with preclinical Alzheimer’s disease will not develop dementia

Study findings published in Alzheimer’s & Dementia found that most individuals with preclinical disease will not develop Alzheimer’s disease dementia during their lifetimes.

The results also showed that lifetime risks of developing dementia vary by age, gender and whether signs or symptoms of the disease are present.

“What we found in this research is that people with preclinical Alzheimer's disease dementia may never experience any clinical symptoms during their lifetimes because of its long and variable preclinical period,” Ron Brookmeyer, PhD, of the department of biostatistics at UCLA School of Public Health, said in a press release. “The high mortality rates in elderly populations are also an important factor as individuals are likely to die of other causes.”

Brookmeyer and Nada Abdalla, PhD candidate, reported the first estimates of the lifetime and 10-year risks of Alzheimer’s disease dementia based on age, gender and biomarker tests for preclinical disease using a multistate model for the disease process along with death rate data in the United States. Specifically, they created a computerized mathematical model using data from longitudinal studies that measured biomarkers with data from thousands of people, to determine the likelihood of Alzheimer’s disease dementia progression, according to the press release.

By disease state, analysis showed that lifetime risks at each age increase by disease state in the following order: normal; neurodegeneration alone; amyloidosis alone; amyloidosis and neurodegeneration; mild cognitive impairment (MCI) with neurodegeneration; and MCI with amyloidosis and neurodegeneration. Researchers found that lifetime risks usually decrease with age for people in any given disease state: the lifetime risk for a woman aged 90 years with only amyloidosis is 8.4%, but is 29.3% for a woman aged 65 years with this same disease state. They noted the risk is greater for the younger patient because the 90-year-old has a shorter life expectancy than a 65-year-old.

The researchers found that the presence of preclinical Alzheimer’s disease does not always signal a high likelihood of Alzheimer’s disease dementia. In addition, the results demonstrated that people aged younger than 85 years with MCI, amyloidosis and neurodegeneration carry a lifetime risk for Alzheimer’s disease dementia of 50% or greater.

“There are numerous critical factors to consider in assessing the value of screening for [Alzheimer’s disease] biomarkers,” the researchers wrote. “Lifetime risks will aid in formulating screening guidelines by identifying groups of persons for whom screening for preclinical [Alzheimer’s disease] may be most useful and by helping interpret the clinical significance of biomarker screening tests for preclinical [Alzheimer’s disease].” – by Savannah Demko

Disclosures: Brookmeyer reports receiving grants from NIH and fees from Takeda Inc.