By 2030, an estimated 78 million people worldwide will be living with dementia, and that number is expected to rise even higher in the following decades. Integrating effective cognitive screening into primary care settings is a practical way to detect and monitor symptoms of cognitive impairment as its prevalence continues its rise.
One long-standing tool used in clinical workflows is the clock drawing test (CDT). This test is a common fixture in dementia screening due to its simplicity and quick administration. 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.
What Is The Clock Drawing Test (CDT) and What Is It Used For?
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 areas commonly affected in dementia.
The clock drawing test is a pen-and-paper cognitive screen that uses a clock drawing to assess various cognitive domains. 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 can also be used to help detect and monitor several neurological disorders. These can include:
- Stroke
- Parkinson’s disease
- Huntington’s disease
- Traumatic brain injuries (TBIs)
- Cerebral vascular disease
- Multiple sclerosis
- Schizophrenia
- Brain tumors or lesions affecting executive function or causing unilateral neglect
- Dementia
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.
What Does the Clock Drawing Test Measure?
Several domains of cognitive function are required to accurately draw a clock. These include:
Executive function
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.
Visuospatial function
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.
Attention
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.
How to Use the Clock Drawing Test to Assess 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.
Performing the Clock Drawing Test
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 test gives patients a blank piece of paper and has them:
- Draw a circle for the clock face
- Place the numbers in the correct order
- Set the hands to a specific time
Variations may include providing a pre-drawn circle, asking patients to copy a completed clock, or repeating the task for comparison. This low-tech, pen-and-paper test is easy to administer and doesn’t require any specialized tools.
Indicators of impaired function in the Clock Drawing Test
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:
- Large or unusual clock size: Patients with Alzheimer’s disease often draw unusually large clocks, suggesting motor or visuospatial issues.
- Graphical difficulties: This may include distorted clock faces, uneven lines, or hard-to-read numbers and clock hands. These graphical issues may be indicators of issues present in vascular dementia.
- Conceptual deficits: Some patients fail to understand the task, to engage numerical memory, or to grasp the concept of a specific time setting. This may lead to them producing incomplete or irrelevant drawings, even in the early stages of dementia.
- Spatial/planning deficit: Clocks with numbers jammed on one side or out of sequence often reflect executive dysfunction. For stroke patients, placing all the numbers on one side can indicate visuospatial neglect.
- Repeating numbers and perseveration: Repeating numbers or drawing more than two hands suggests poor cognitive flexibility, which is often seen in Alzheimer’s disease.
Scoring Methods for Clock Drawing Test Results
There are over twenty different scoring systems for clock drawing test interpretation. A few of the more common clock test scoring methods include:
- Pass/Fail: This scoring system looks at whether or not instructions were followed correctly. For example, the Mini-Cog allocates 2 points to the Clock Drawing Test, and any abnormality results in a score of 0.
- The Shulman Method: In this method, the clock’s representation is scored on a scale of 0-5, with more errors resulting in a lower score.
- The Sunderland Method: This is a more detailed 10-point scoring system that focuses on each specific clock-drawing error.
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.
Strengths and Limitations of the Clock Drawing Test for Dementia
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:
Strengths
Some strengths of the Clock Drawing Test include:
- Quick and easy to administer
- May be reimbursable as part of a cognitive assessment for dementia under CPT code 99483
- Both the process and the outcome can be assessed
Limits
While a clock drawing can reveal a lot about a patient’s cognition, this test has its limits, including:
- A lack of sensitivity in detecting mild dementia or MCI
- Requires manual scoring by trained clinicians
- Subjective interpretation without standardized scoring or cutoffs
- Educational background can affect performance
- Patients with motor or visual impairments may be unfairly scored
- Repetition or coaching can influence results
- A lack of detailed cognitive information means additional assessment is needed for diagnosis or predicting real-world abilities.
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.
How Digital Cognitive Tests Help Improve Cognitive Impairment Diagnostic Processes
While the Clock Drawing Test for dementia is a quick and simple screen, digital cognitive assessments like Creyos Health’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:
- Integrated behavioral health questionnaires: Capture indicators of comorbidities for a comprehensive view of patient health.
- Automatic scoring and reporting: Digital tasks are automatically scored and added to easy-to-read reports. Track cognitive changes over time to monitor progression or improvement.
- Seamless EHR integration: Multiple providers can access and share patient cognitive data, improving coordinated care.
- Accessible instruction: Leverage both written and auditory instructions, as well as practice sessions in multiple languages, for more accessible testing.
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.
Written By Avi Meehan
Avi Meehan is an author, editor, and SEO copywriter based in Ontario, Canada. They write about a wide range of topics, including nonprofit and event management, cognition and mental health, and more. Through their legacy memoir writing service, Recollections, they help aging individuals explore and document their life stories.
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.