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Amyloid positivity in cognitively sound patients may indicate early Alzheimer's disease

The development of Alzheimer’s disease pathology may begin as early as 30 years of age, leaving a significant amount of time, approximately 20 to 30 years, between amyloid positivity and the onset of dementia, according to recently published data in JAMA.

“This study has several implications for understanding the development of [Alzheimer’s disease]. The observation that key risk factors for Alzheimer’s disease-type dementia are also risk factors for amyloid positivity in cognitively normal persons provides further evidence for the hypothesis that amyloid positivity in these individuals reflects early [Alzheimer’s disease],” the researchers wrote.

Using previously published studies obtained from MEDLINE and Web of Science databases, researchers evaluated the prevalence of amyloid pathology as measured with biomarkers in patients with normal (n = 2,914), subjective (n = 697) or mild (n = 3,972) cognitive impairment. In all, 55 studies were analyzed, with patients ranging from age 18 years to 100 years.

Among patients with normal cognition, the presence of amyloid pathology increased from 10% at age 50 to 44% at age 90. Those with subjective cognitive impairment had an increase from 12% at age 50 to 43% at age 90, and patients with mild cognitive impairment saw an increase from 27% at age 50 to 71% at age 90.

Participants who were APOE-ε4 carries had 2 to 3 times higher rates of amyloid pathology prevalence compared with noncarriers.

Patients who were highly educated were more likely to have amyloid positivity compared with those with less formal education.

Of significance, the researchers noted that Alzheimer’s disease pathology can develop as early as age 30, meaning that a 20 to 30 year interim between amyloid positivity and dementia may exist, leaving a large portion of time for preventative treatments.

“Because of the uncertainty about whether and when an amyloid-positive individual without dementia will develop dementia, amyloid positivity in these individuals should not be equated with impending clinical dementia but rather be seen as a risk state,” researchers wrote. – by Casey Hower

Disclosure: The researchers report no relevant financial disclosures.