Predictors of Progression from Mild Cognitive Impairment to Dementia in the Placebo-Arm of a Clinical Trial Population

Abstract

We studied the predictive value of cognitive performance, vascular risk factors, apolipoprotein E (APOE) genotype, and structural brain changes on MRI, on progression to dementia in post hoc analyses of 426 placebo patients (mean age 71 years; 55% women) with mild cognitive impairment (MCI) who participated in a previously published large multi-center clinical trial (Gal-Int-11). The ADAS-cog/MCI test, the New York University Paragraph Recall Test, and the Digit Symbol Coding Test were available at baseline, as were vascular risk factors and APOE genotype. Medial temporal lobe atrophy (MTA), white matter hyperintensities (WMH) and lacunes were assessed on MRI. Over two years of follow-up, 81 patients (19%) converted to dementia, while 345 patients (81%) remained stable. Results of Cox proportional-hazards regression analysis showed that higher age, worse cognitive test performance, presence of an APOE ε4 allele, and higher MTA scores on MRI increased the risk of progression to dementia in univariate analyses. Vascular risk factors, and WMH and lacunes on MRI, were not associated with progression to dementia. Lower performance on the ADAS-cog/MCI test (HR 1.08 per point increase; 95% CI 1.06-1.10) and Delayed recall test (HR 0.76 per point increase; 95% CI 0.68-0.85), as well as higher MTA scores on MRI (HR 1.33 per point increase; 95% CI 1.00-1.77) were independent predictors of progression to dementia in a step-wise Cox proportional-hazards model with age and gender forced into the model. We conclude that global cognitive function, episodic memory performance, and MTA on MRI independently predict progression to dementia in patients with MCI.