Self-reported memory impairment and brain PET of amyloid and tau in middle-aged and older adults without dementia.

BACKGROUND

Whether perceived changes in memory parallel changes in brain pathology is uncertain. Positron emission tomography (PET) scans using 2-(1-{6-[(2-[F-18]fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile (FDDNP) can measure levels of amyloid plaques and tau neurofibrillary tangles in vivo. Here we investigate whether degree of self-reported memory impairment is associated with FDDNP-PET binding levels in persons without dementia.

METHODS

Fifty-seven middle-aged and older adults without dementia (mean age ±standard deviation = 66.3 ± 10.6 years), including 25 with normal aging and 32 with mild cognitive impairment (MCI), were assessed. The outcome measures were the four factor scores of the Memory Functioning Questionnaire (MFQ) (frequency of forgetting, seriousness of forgetting, retrospective functioning, and mnemonics use) and FDDNP-PET binding levels in medial temporal, lateral temporal, posterior cingulate, parietal, frontal, and global (overall average) regions of interest.

RESULTS

After controlling for age, higher reported frequency of forgetting was associated with greater medial temporal (r = -0.29, p = 0.05), parietal (r = -0.30, p = 0.03), frontal (r = -0.35, p = 0.01), and global FDDNP-PET binding levels (r = -0.33, p = 0.02). The remaining MFQ factor scores were not significantly associated with FDDNP-PET binding levels, and no significant differences were found between normal aging and MCI subjects. Item analysis of the frequency of forgetting factor revealed five questions that yielded similar results as the full 32-question scale (r = -0.52, p = 0.0002).

CONCLUSIONS

These findings suggest that some forms of memory self-awareness, in particular the reported frequency of forgetting, may reflect the extent of cerebral amyloid and tau brain pathology.