Prediction of dementia by subjective memory impairment: effects of severity and temporal association with cognitive impairment.

CONTEXT: Subjective memory impairment (SMI) is receiving increasing attention as a pre-mild cognitive impairment (MCI) condition in the course of the clinical manifestation of Alzheimer disease (AD).

OBJECTIVES: To determine the risk for conversion to any dementia, dementia in AD, or vascular dementia by SMI, graded by the level of SMI-related worry and by the temporal association of SMI and subsequent MCI.

DESIGN: Longitudinal cohort study with follow-up examinations at 1(1/2) and 3 years after baseline.

SETTING: Primary care medical record registry sample.

PARTICIPANTS: A total of 2415 subjects without cognitive impairment 75 years or older in the German Study on Aging, Cognition and Dementia in Primary Care Patients.

MAIN OUTCOME MEASURES: Conversion to any dementia, dementia in AD, or vascular dementia at follow-up 1 or follow-up 2 predicted by SMI with or without worry at baseline and at follow-up 2 predicted by different courses of SMI at baseline and MCI at follow-up 1.

RESULTS: In the first analysis, SMI with worry at baseline was associated with greatest risk for conversion to any dementia (hazard ratio [HR], 3.53; 95% confidence interval [CI], 2.07-6.03) or dementia in AD (6.54; 2.82-15.20) at follow-up 1 or follow-up 2. The sensitivity was 69.0% and the specificity was 74.3% conversion to dementia in AD. In the second analysis, SMI at baseline and MCI at follow-up 1 were associated with greatest risk for conversion to any dementia (odds ratio [OR], 8.92; 95% CI, 3.69-21.60) or dementia in AD (19.33; 5.29-70.81) at follow-up 2. Furthermore, SMI at baseline and amnestic MCI at follow-up 1 increased the risk for conversion to any dementia (OR, 29.24; 95% CI, 8.75-97.78) or dementia in AD (60.28; 12.23-297.10), with a sensitivity of 66.7% and a specificity of 98.3% for conversion to dementia in AD.

CONCLUSION: The prediction of dementia in AD by SMI with subsequent amnestic MCI supports the model of a consecutive 3-stage clinical manifestation of AD from SMI via MCI to dementia.