The Clinical Dementia Rating (CDR) scale shows dementia severity, from no impairment to severe dementia. It shows how memory and thinking changes affect daily independence, not only test scores. The rating comes from separate interviews with the person and a close informant. A clinician compares both accounts across memory, daily function, and personal care.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- How is the CDR interview done?
- What do the numbers mean?
- Why do trials use Sum of Boxes?
- What are its limits for families?
How is the CDR interview done?
A clinician interviews the patient and a close informant separately. Together they cover six domains: memory, orientation, judgment and problem-solving, community affairs, home and hobbies, and personal care.
According to InformedHealth, the InformedHealth guide to the CDR scale says the interview takes about 30 minutes and assesses thinking plus everyday function. That pairing matters because family members often notice missed bills, unsafe cooking, or withdrawn hobbies first. The clinician weighs both views to judge independence, not just answers in the room.
What do the numbers mean?
Each domain is rated 0, 0.5, 1, 2, or 3. Memory carries the most weight in the overall global score.
The staging method was developed at Washington University School of Medicine, as described by the Knight ADRC CDR scoring rules. A 0.5 often means subtle lapses with mostly preserved independence. A 1 or higher means thinking loss clearly limits daily tasks and needs more support.
- 0: no impairment
- 0.5: very mild or questionable impairment
- 1: mild dementia
- 2: moderate dementia
- 3: severe dementia
Why do trials use Sum of Boxes?
The Sum of Boxes adds the six domain scores for a 0-18 total. Typical bands are about 0.5-4.0 very mild, 4.5-9.0 mild, 9.5-15.5 moderate, and 16-18 severe. The total detects small changes better than the single global stage.
That sensitivity explains its trial role. According to the Regulatory Affairs Professionals Society, the RAPS analysis of FDA guidance influence says FDA's 2013 draft guidance recommended composites such as CDR-SB, after which its use as a primary endpoint rose from 1.9% to 16.7%. Early-Alzheimer's participants often start near 2-6, so a slower rise means decline slowed.
What are its limits for families?
CDR is a clinician judgment, not a brain scan. It needs a trained rater and a knowledgeable informant, so ratings can vary.
It does not itself show amyloid or tau pathology needed to confirm Alzheimer's cause. Bring someone who sees weekly routines, medications, driving, cooking, and money management. Ask which domain changed most, what support fits now, and when to recheck if function slips.
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