Patients with
mild cognitive impairment are at an increased risk of progression to
Alzheimer's disease. However, not all patients with
mild cognitive impairment progress, and it is difficult to accurately identify those patients who are in the
prodromal stage of
Alzheimer's disease. In a recent paper, Koivunen and colleagues report that
Pittsburgh compound-B, an
amyloid-beta positron emission tomography
ligand, predicts the progression of patients with
mild cognitive impairment to
Alzheimer's disease. Of 29 subjects with
mild cognitive impairment, 21 (72%) had a positive
Pittsburgh compound-B positron emission tomography baseline scan. In their study, 15 of these 21 (71%) patients progressed to
Alzheimer's disease, whilst only 1 out of 8 (12.5%)
Pittsburgh compound-B-negative patients with
mild cognitive impairment did so. Moreover, in these
mild cognitive impairment patients, the overall
amyloid burden increased approximately 2.5% during the follow-up period. This is consistent with other longitudinal
amyloid imaging studies that found a similar increase in
amyloid deposition over time in patients with
mild cognitive impairment. These studies together challenge current theories that propose a flattening of the increase of brain
amyloid deposition already in the preclinical stage of
Alzheimer's disease. These findings may have important implications for the design of future clinical trials aimed at preventing progression to
Alzheimer's disease by lowering the brain
amyloid-beta burden in patients with
mild cognitive impairment.