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Home › Research › Answers › This question

What does the ADAS-Cog measure, and what does a change in score mean?

The ADAS-Cog is the cognitive subscale of the Alzheimer's Disease Assessment Scale, scored in points where higher scores mean greater impairment; the 11-item version (ADAS-cog11) ranges from 0 to 70 and the 14-item version from 0 to 90. A change of 3 points is the threshold a 2024 review reported as meaningful in mild Alzheimer's disease, and recent anti-amyloid trials found average differences below published thresholds.

What the studies found

The two bapineuzumab phase 3 trials, published in 2014, used the 11-item cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-cog11) as a primary outcome, with scores ranging from 0 to 70 and higher scores indicating greater impairment. A rising score therefore means decline. At week 78 the between-group differences in change from baseline were -0.2 in the carrier study and -0.3 in the noncarrier study at the 0.5-mg-per-kilogram dose.

Later trials report longer versions. The 2021 donanemab phase 2 trial listed the 13-item cognitive subscale (ADAS-Cog 13) as a secondary outcome beside the CDR-SB, the ADCS-iADL and the MMSE. The 2023 lecanemab trial used the 14-item version (ADAS-cog14; range, 0 to 90; higher scores indicate greater impairment) as a key secondary end point, with the CDR-SB as the primary end point.

A 2010 psychometric evaluation used data from three donepezil trials in 1421 people with mild-to-moderate Alzheimer's disease. The scale as a whole was reliable (Cronbach's alpha 0.84; test-retest intraclass correlation 0.93) and correlated with the MMSE at -0.63. At the level of its components, 7 of 11 had substantial ceiling effects (range 40-64%), and the authors concluded that most components were too easy for many patients in this sample.

A 2018 narrative review recorded that the scale was developed in the 1980s to assess cognitive dysfunction in Alzheimer's disease and has since been used in pre-dementia studies despite concerns about detecting important changes at milder stages. A 2012 analysis of 811 Alzheimer's Disease Neuroimaging Initiative participants added executive functioning and functional ability items to build the ADAS-Cog-Plus, aiming for better responsiveness in mild cognitive impairment.

A 2015 analysis of 1709 participants from the Alzheimer's Disease Neuroimaging Initiative lined up scores on the ADAS-Cog, the MMSE and the CDR-SOB. It found multiple inflections in CDR-SOB and ADAS-Cog scores within a given MMSE score, suggesting that those scales are more precise in measuring the severity of cognitive dysfunction than the MMSE.

What a change in score means

A 2024 rapid systematic review retrieved ten articles on minimal clinically important differences (MCIDs). For mild cognitive impairment, a change of +2 to +3 points on the ADAS-Cog was considered meaningful; for mild Alzheimer's disease, a change of +3. The review found that MCIDs were higher for more severe stages of Alzheimer's disease.

A 2012 cohort of 41 outpatients from 59 Alzheimer's Disease Neuroimaging Initiative sites tried to establish the minimal clinically relevant change in mild Alzheimer's disease by comparing ADAS-Cog change with clinicians' judgement of worsening over 6 and 12 months. A 2021 distribution-based analysis of 37 randomized trials (10,006 patients) derived ADAS-Cog MCIDs of 4 at 0.4 SDs and 5 at 0.5 SDs using baseline SDs, and 2.6 and 3.2 using mean change SDs.

In the 1998 donepezil trial of 468 patients, the mean drug-placebo differences at end point were 2.5 units for 5 mg/d and 3.1 units for 10 mg/d on the ADAS-cog.

A 2024 meta-analysis of 19 publications with 23,202 participants found small improvements over placebo on the ADAS-Cog-11 to -14 score (standardized mean difference = -0.07; 95% CI, -0.10 to -0.04) with anti-amyloid antibodies, and none of the changes exceeded the MCID. A 2026 updated review of gantenerumab (six trials) likewise reported statistically significant ADAS-Cog13 improvements that remain below accepted MCID thresholds.

What remains uncertain

There is no single agreed number. The 2024 review gives +2 to +3 for mild cognitive impairment and +3 for mild Alzheimer's disease, while the 2021 distribution-based method gave values from 2.6 to 5 depending on the standard deviation used, and the review says input from patients and caregivers will be needed to derive more meaningful thresholds. The 2024 meta-analysis also notes that MCID thresholds are debated.

The library records describe the ADAS-Cog 13 only as the 13-item cognitive subscale; none gives its score range, so this page does not state one. The ranges given here, 0 to 70 and 0 to 90, are those the trial reports state for the 11-item and 14-item versions.

Whether the scale detects change at early stages is itself questioned: the 2018 review cites concerns about milder stages, and the 2010 evaluation found ceiling effects in 7 of 11 components. A point change on a group average in a trial is not the same as a change a person or family would notice, and a clinician who knows the person can say what a score means for them.

This page describes what published studies in alzhub's library report. It is not medical advice and does not apply to any one person. Where a decision would follow, a clinician who knows the person is the one who can say what a result or a choice means for them.

Questions

What do the ADAS-Cog 11 and ADAS-Cog 13 measure?
Both are cognitive subscales of the Alzheimer's Disease Assessment Scale, one with 11 items and one with 13 items, reported as scores where higher means greater impairment. The 11-item version ranges from 0 to 70.
Is a higher ADAS-Cog score better or worse?
Worse. In the trials cited here, higher scores indicate greater cognitive impairment, so a score that rises over time means decline.
How many points is a meaningful change on the ADAS-Cog?
A 2024 rapid review reported +2 to +3 points for mild cognitive impairment and +3 for mild Alzheimer's disease, and a 2021 distribution-based analysis derived values between 2.6 and 5. The figure depends on the method and the stage.
Did treatments reach that threshold?
In a 2024 meta-analysis of 19 publications, none of the anti-amyloid antibody changes, including lecanemab, aducanumab and donanemab, exceeded the MCID. In the 1998 donepezil trial the mean drug-placebo difference was 3.1 units at 10 mg/d.

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