The Clock-Drawing Test for Alzheimer’s/Dementia : Everything Caregivers Need to Know

What is the Clock-Drawing Test?

The Clock-Drawing Test, also known as the CDT, is a fast and simple way of spotting brain dysfunction, including warning signs of Alzheimer’s disease and other related dementias. The CDT can be administered by non-professionals in the comfort of one’s home and all you need is piece of paper, a pencil and a few minutes of time. Although the test may seem basic, it’s been used as an effective screening tool by medical professionals for more than 100 years. And its results can a clear and powerful visual statement telling families that something is wrong with their loved ones.

It’s important to remember that the CDT should not be used on its own to diagnose dementia. A true diagnosis requires medical professionals and multiple tests and screens. When used at home, the results of the CDT should only be used by families to decide if their loved one should see their primary care provider about the possibility of Alzheimer’s disease or other dementias.

How Does it Work

The Clock-Drawing Test (CDT) is very straightforward. The test taker, who has been showing some signs of dementia, is given a pencil and a piece of paper. They are then asked to draw an analog clock (with minute and hour hands) showing the time as “10 minutes past 11.” There is no time limit, but drawing the clock should take about a minute.

If the clock is drawn abnormally in any way, it indicates the possibility of dementia and a need for further evaluation by a doctor.

Professionals can use elaborate scoring methods for the CDT, assigning points based on the positioning of numbers and hands, as well as other factors. Studies are mixed on whether these complicated scoring techniques are effective at determining the severity or stage of dementia. But the consensus among experts is the CDT is an effective pass/fail test that can be used to see if more testing is required.

Advantages of Early Diagnosis

Despite its simplicity, the CDT can help determine if someone is in the early stages of of Alzheimer’s disease and other dementias. This is critical because medications and therapies are more effective the sooner they begin. There is no cure for Alzheimer’s disease and related dementias, but there are ways to manage symptoms, especially if they are detected early. Some of these early signs include:

• Difficulty planning or problem solving
• Difficulty completing familiar tasks
• Losing track of time and place
• Misplacing items
• Problems speaking or writing
• Mood swings and changes in personality (becoming less social)

Pros and Cons

The CDT was originally developed in the 1900s to evaluate soldiers with head injuries. While it is still used to assess the severity of traumatic brain injury (TBI), since the 1980s the primary use for the CDT is to gauge whether or not someone may be developing Alzheimer’s disease or another related dementia. The scientific community, including the Alzheimer’s Association, widely agrees that the CDT is a useful component of screening for cognition problems, including dementia.

Pros:

• Speed. The test only takes a few minutes to administer and interpret.
• Simplicity. You don’t need training to administer the test.
• Cost. No expensive equipment or appointments are required, just a pen or pencil and paper.
• Tolerability. Someone who bristles at testing may not mind being asked to perform this simple task.

Cons:

The CDT is considered a sensitive and accurate test. The only potential cons are:

• The results can be misread if not done by a medical professional.
• Detects abnormalities in brain health early, but it does not show what kind of dementia your loved one has

Accuracy

The accuracy of the CDT has been measured many times and most studies show it be 85% accurate in detecting people who do have dementia (which is known as the test’s “sensitivity”) and it’s also 85% accurate in detecting people who do not have dementia (known as the test’s “specificity.”)

How can such a simple test be that accurate? Consider what’s required:

• Verbal understanding
• Spatial knowledge
• Visual memory
• Abstract thinking

First, a person has to hear the instruction and then turn those words into the correct action. It takes the ability to think to turn “Draw a clock” into the act itself. Unfortunately for people with Alzheimer’s disease and other dementias, this thinking ability is compromised. Hearing an instruction and acting on it is difficult.

It also takes planning or an understanding of the steps involved. The brain has to be able to know to first draw a circle, then numbers and then the hands. This also requires visual memory or remembering what a clock looks like because you’ve seen one before.

Finally, there’s abstract thinking. The reason it’s a good idea to ask for “10 minutes after 11,” is because the mind has some work to do. Someone whose brain doesn’t correctly process information might draw hands pointing to the 10 and the 11. It takes a little more effort to know that the “10 after” means drawing an arrow toward the 2.

A drawn clock is also a powerful symbol for friends and loved ones to see. That single image can represent a loved one’s mental state, while the numbered score on a Q-and-A test just doesn’t have the impact of a clock with obvious mistakes.

How to Administer the Clock Drawing Test

Interpreting the Results

Again, it’s important to reiterate that the Clock-Drawing Test (CDT) should not be used on its own to diagnose dementia. It’s a useful tool and that’s widely embraced by the medical community, but the CDT is just a small step in evaluating whether someone is developing dementia. Further testing by a physician is essential before definitively saying that someone has Alzheimer’s disease or any another dementia.

That being said, after your loved one draws the clock, you can evaluate the image to see what might be wrong with it. Since different dementias impact different parts of the brain, several aspects of the drawing can be revealing:

The Size of the Clock. Patients with dementia caused by Parkinson’s disease or Huntington’s disease are prone to draw a smaller clock (less than two inches), while people with Alzheimer’s disease tend to draw bigger clocks (more than 10 inches).

Fixating on Time. Being primarily focused on getting the hands of the clock in the right position so the time is correct is more common in Alzheimer’s disease and Parkinson’s disease dementia than with other dementias.

Graphical Errors. If the clock looks essentially correct, but is messy (wavy or broken lines), it may be a sign of Huntington’s disease or vascular dementia as opposed to Alzheimer’s disease.

Radically Wrong If the clock doesn’t even look like a clock, chances are the person is dealing with Alzheimer’s disease rather than Huntington’s, Parkinson’s, vascular dementia or frontotemporal dementia.

Spatial Errors. If there are big gaps, numbers outside the circle or numbers on only one side of the circle, it could be an indication of Parkinson’s disease dementia, Lewy body dementia or vascular dementia, but it’s less often a sign of Alzheimer’s.

See images of Clock-Drawing Tests results here.

Alternatives and Comparisons

Compared to the Modified Clinical Dementia Rating (CDR) 

This is another test that is fast, easy, and can be taken by family members and caregivers without medical training. It simply involves answering questions about a loved one’s behavior. Nothing is required of the individual who may have dementia. Click here for an online version of the Modified Clinical Dementia Rating Test.

Compared to the Mini-Mental State Exam

The Mini-Mental State Exam (MMSE) is the most common tool for assessing the severity of a person’s dementia. Usually, anyone who is showing signs of dementia would take the CDT first and then, if the clock was drawn incorrectly, they could take the MMSE. Click here for more information about the MMSE.