By 2030, an estimated 78 million people worldwide will be living with dementia, according to Alzheimer's Disease International, and that number is expected to rise even higher in the following decades. Integrating cognitive screening into primary care is a practical way to detect early signs of cognitive impairment and monitor them over time.
The clock drawing test (CDT) is a pen-and-paper cognitive screen in which a patient draws a clock face, places the numbers, and sets the hands to a specified time. Long-standing in clinical practice, it is a common fixture in dementia screening because it is simple and quick to administer. Here, we review how to administer and interpret the clock drawing test, its strengths and limitations, and explore how pairing it with objective digital assessments can further enhance clinical decision-making.
Article Highlights
The clock drawing test is a pen-and-paper screen in which a patient draws a clock face, numbers it, and sets the hands to a given time.
As a cognitive screen, the CDT uses a single drawing to assess several cognitive domains at once. The test is as simple to administer as it sounds; patients are asked to draw a clock. Providers can use the process of drawing a clock and the resulting image to determine whether or not a patient's cognition is potentially impaired.
The clock drawing test is primarily used to screen for dementia, making it a valuable tool in primary care for identifying and tracking cognitive decline. Performing the task requires the involvement of several cognitive functions at once, including executive function, visuospatial abilities, and working memory. All of these are commonly affected in dementia.
The clock drawing test can also help detect and monitor several neurological conditions. These can include:
It’s worth noting that the clock drawing test is not as sensitive as other cognitive tests for dementia. Clinicians often use this test alongside other assessments for a more comprehensive understanding of a patient’s cognition. For example, the Mini-Cog uses both the clock drawing test and a memory test, combining the scores from both.
Several domains of cognitive function are required to accurately draw a clock. These include:
The test can be used to analyze patients’ executive function, including planning, organizing, and problem-solving skills. These abilities are often compromised in instances of dementia. Drawing a clock requires the patient to understand the task, plan where all the numbers go, and position the hands correctly at a specific time.
Patients must correctly place numbers around the clock face and draw hands at the right angles. This test tests spatial awareness and coordination. Impaired visuospatial function is a key symptom of stroke, and the clock drawing test can be a helpful visuospatial assessment tool.
The clock drawing test can be used to test a patient’s attention. Sustained and selective attention are necessary to complete the clock drawing task without errors or omissions. Distractibility and inattention are common symptoms of impaired cognition.
The clock drawing test is a quick and practical cognitive assessment tool that providers can use to better understand patients’ cognition and help decide when they may need further evaluation for disorders like dementia.
Part of the clock drawing test’s strength lies in its flexibility. In its early iteration, patients were asked to set the hands on a pre-drawn clock to ten minutes after 11 o’clock.
Today, the current protocol gives patients a blank piece of paper and asks them to:
Common variations include:
This low-tech, pen-and-paper test is easy to administer and doesn’t require any specialized tools.
When interpreting a clock drawing test for potential cognitive impairment, providers will look for certain errors to see which cognitive functions may or may not be affected.
Some indicators of impaired brain function on a clock drawing test include:
There are over twenty different scoring systems for clock drawing test interpretation. A few of the more common clock test scoring methods include:
| Scoring method | Scale | What it assesses |
|---|---|---|
| Pass/Fail | 2 points within the Mini-Cog | Whether instructions were followed correctly. Any abnormality results in a score of 0. |
| The Shulman Method | 0 to 5 | The clock’s overall representation, with more errors resulting in a lower score. |
| The Sunderland Method | 0 to 10 | Each specific clock-drawing error, in more detail. |
No matter the scoring system used, passing the clock drawing test comes down to how well the clock is drawn. This means how appropriately spaced the image is and how accurately the numbers are placed. It also means that the clock hands are drawn to correctly show the instructed time.
There is some subjectivity involved in scoring the clock drawing test. Scoring involves clinical judgments to determine differences in the image drawn. For example, “hands significantly off course” is a subjective judgment that may have different interpretations depending on who is scoring each clock. That said, in the hands of trained dementia specialists, the reliability and accuracy of the test can be high.
The clock drawing test for dementia is a widely used screening tool, but like any quick pen-and-paper screener, it has its strengths and limitations:
Some strengths of the clock drawing test include:
While a clock drawing can reveal a lot about a patient’s cognition, this test has its limits, including:
The clock drawing test is one way to identify severe overall cognitive impairment, but it doesn’t provide detailed, domain-specific data. When detailed information is needed to help diagnose or track disruptions to brain health, objective cognitive assessments can be used alongside or instead of the clock drawing task.
While the clock drawing test for dementia is a quick and simple screen, digital cognitive assessments like the Creyos platform’s cognitive screens make it easier to detect and understand potential cognitive impairment. This suite of scientifically backed tools gathers objective data that can work in conjunction with traditional screens like the clock drawing test.
Creyos includes testing that uses a wide range of cognitive tasks targeting multiple domains linked to specific brain regions, providing a richer, more detailed profile than a single test.
Some key benefits of using Creyos include:
Additionally, Creyos makes it easy for providers to offer both remote and in-person testing options. The Center for Healthy Brain Aging (CHeBA) used Creyos to run the world’s largest dementia trial entirely online. In clinical usage, Creyos helps screen thousands of people for dementia, as well as track their brain health long-term, without overloading providers with work.
For over 100 years, the clock drawing test has been a quick way to screen for cognitive impairment. While easy to access, effective personalized care often requires more detailed cognitive assessment tools.
Reviewed by Mike Battista, Director of Science & Research at Creyos
Mike Battista specializes in brain health, cognition, and neuropsychological testing. He received his PhD in personality and measurement psychology at Western University in 2010 and has been doing fun and useful stuff in the intersection between science and technology ever since.