Memory impairment, but not cerebrovascular disease, predicts progression of MCI to dementia

BACKGROUND: Mild cognitive impairment (MCI) is widely viewed as the transition phase between normal aging and Alzheimer disease (AD). Given that MCI can also result from cerebrovascular disease (CVD), the authors used clinical, MRI, and cognitive measures of AD and CVD to test the hypothesis that CVD increases the likelihood of progression from MCI to dementia within 3 years. OBJECTIVE: To examine the impact of CVD on progression of MCI to dementia. METHODS: Fifty-two consecutive patients with MCI (71% men) including many with symptomatic CVD were longitudinally evaluated for 3.1 +/- 1.3 years. MCI was defined as a Clinical Dementia Rating Scale (CDR) score of 0.5. Dementia was defined as progression to a CDR score of > or =1.0. RESULTS: Forty-four percent of the MCI patients had MRI infarcts, 50% of which were symptomatic. Thirty-three percent of patients progressed to dementia, and 37.8% of these had MRI infarcts. Clinically probable or possible AD was diagnosed in approximately 82% of converters. Of the clinical and MRI measures, only hippocampal volume was associated with increased risk to progression (hazard ratio HR = 0.31 95% CI 0.1 to 0.92, p = 0.03). When neuropsychological measures were included in the analysis, memory (HR = 0.90 95% CI 0.84 to 0.96, p = 0.002) and executive function (HR = 0.96 95% CI 0.92 to 1.0, p = 0.045) were associated with increased risk of dementia progression, whereas APOE genotype, cerebrovascular risk factors, clinical stroke, presence or absence of lacunes, and extent of white matter hyperintensities did not predict progression. CONCLUSION: Within a heterogenous group of MCI patients, including many with clinically significant CVD, baseline memory and executive performance significantly predicted likelihood to develop dementia.