Featured ArticleProgression of Alzheimer's disease as measured by Clinical Dementia Rating Sum of Boxes scores

BackgroundThis study examined rates of dementia progression as ascertained by the Clinical Dementia Rating Sum of Boxes (CDR-SB) for symptomatic Alzheimer's disease (sAD), and assessed participant characteristics as predictors of CDR-SB progression.MethodsParticipants (n = 792) were enrolled in longitudinal studies at an Alzheimer's Disease Research Center, received a diagnosis of sAD with a global CDR of 0.5 (n = 466) or 1 (n = 326), and had at least one follow-up assessment. Progression in CDR-SB over time as a function of baseline global CDR was examined.ResultsA longitudinal increase (P < .0001) in CDR-SB was observed. The annual rate of change in CDR-SB scores was 1.43 (standard error [SE] = 0.05) in the CDR 0.5 sample and 1.91 (SE = 0.07) in the CDR 1 sample. For participants followed from the beginning of the CDR stage, time to progression to a higher global CDR was longer for individuals who were CDR 0.5 (3.75 years; 95% confidence interval [CI]: 3.18-4.33) than those who were CDR 1 at baseline (2.98 years; 95% CI: 2.75-3.22). In the total CDR 0.5 sample, the significant predictors of progression to the next global CDR stage (P < .01) were age at first sAD diagnosis and apolipoprotein E4 genotype.ConclusionsThe study findings are relevant to sAD clinical trial design and accurate, reliable ascertainment of the effect of disease-modifying treatments.