Disagreement between self- and informant-reported memory complaints and progression of mild cognitive impairment to dementia.

Objectives: To evaluate whether discrepancy between patient and informant reports of memory deficits can be used as a proxy of impaired awareness of memory function in Mild Cognitive Impairment (MCI) and to determine its prognostic value in conversion to dementia.

Method: We conducted a longitudinal study including 128 older adults with memory complaints, diagnosed with MCI. At baseline, participants were assessed for central Alzheimer's Disease biomarkers, memory complaints (Subjective Memory Complaints scale, SMC) and cognition (MMSE). Participants were followed annually (mean follow-up time 43.3 months) to detect progression to dementia, defined by clinical assessment and Clinical Dementia Rating Scale.

Results: Self- and informant-reported SMC scores were used to create the variable 'SMC discrepancy', classifying participants as underreporters, overreporters and congruent reporters. Underreporters showed lower cognitive performance ( = 0.021), which did not translate into higher self-report SMC ( = 0.092). They had the highest informant-reported SMC ( < 0.001) and greater amyloid ( = 0.020), tau ( = 0.005) and p-tau ( = 0.034) burden. Underreporting of memory deficits was associated with a 4.31-fold increased risk of conversion to dementia ( = 0.001).

Conclusion: Patients' underreporting of memory deficits independently predicted disease progression. Informant-based reports were consistent with changes in AD biomarkers, suggesting that patients' underreporting was due to impaired awareness of memory deficits.