Clinical Dementia Rating (CDR) Scale

When to use

• Staging the severity of cognitive impairment and dementia in a patient with a known or suspected neurodegenerative disorder.
• Tracking disease progression over time using the sum-of-boxes score, e.g. in clinical trials.

Formula

Six domains (memory, orientation, judgment/problem solving, community affairs, home/hobbies, personal care) are each rated 0, 0.5, 1, 2, or 3 (personal care has no 0.5 option). Memory is the primary category. Global CDR = memory score if at least 3 of the 5 secondary domains match it; otherwise the global score shifts toward whichever side (higher or lower than memory) has 3 or more secondary domains, using the modal score on that side. Sum of boxes (CDR-SB) is the simple sum of all six domain scores (range 0-18).

Pearls and pitfalls

• The global CDR (0, 0.5, 1, 2, 3) is used for staging; the sum of boxes is more sensitive to change and preferred for longitudinal/trial use.
• Requires a semi-structured interview with the patient and a reliable informant; it is not a self-report questionnaire.
• This tool implements the published anchoring rules (memory as primary category; explicit rules for memory = 0 and 0.5); in the small minority of box-score combinations that are genuinely ambiguous, the result defaults toward the memory score and should be cross-checked against the full scoring worksheet.

References

1. Morris JC. The Clinical Dementia Rating (CDR): current version and scoring rules. Neurology. 1993;43(11):2412-4.