Can the Clinical Dementia Rating Scale Identify Mild Cognitive Impairment and Predict Cognitive and Functional Decline?

Background: The Clinical Dementia Rating Scale (CDR) is used to rate dementia severity. Its utility in diagnosing mild cognitive impairment (MCI) and its predictive value remain unknown.

Aims: The aim of this study was to examine the association between CDR scores and expert MCI diagnosis, and to determine whether baseline CDR scores were predictive of cognitive or functional decline and progression to dementia over 6 years.

Methods: At baseline, the sample comprised 733 non-demented participants aged 70-90 years from the longitudinal Sydney Memory and Ageing Study. Global and sum of boxes CDR scores were obtained at baseline. Participants also received comprehensive neuropsychological and functional assessment as well as expert consensus diagnoses at baseline and follow-up.

Results: At baseline, CDR scores had high specificity but low sensitivity for broadly defined MCI. The balance of sensitivity and specificity improved for narrowly defined MCI. Longitudinally, all baseline CDR scores predicted functional change and dementia, but CDR scores were not predictive of cognitive change.

Conclusion: CDR scores do not correspond well with MCI, except when MCI is narrowly defined, suggesting that the CDR taps into the more severe end of MCI. All CDR scores usefully predict functional decline and incident dementia.