People with Alzheimer’s disease and other forms of dementia can greatly benefit from an early diagnosis. It means they can promptly access care and treatment options, and can plan ahead while they are still able to make important decisions. It also gives both the person and their caregivers a chance to learn about the disease and set realistic expectations together.
However, early symptoms of dementia are very subtle, vague and vary between people. While there are a variety of cognitive assessments available, the clock drawing test is a quick and easy way to screen for dementia, including Alzheimer’s disease.
This nonverbal screening tool involves drawing a clock on a piece of paper with numbers, clock hands, and a specific time. To do so requires understanding the placement of the hands on a clock and interpreting the time they are intended to represent. This ability is often lost in people with early stage dementia.
At Baycrest, Dr. Morris Freedman, Head of Neurology and Scientist at Baycrest’s Rotman Research Institute, uses the free-drawn clock test because it is the most sensitive. In this test, a person is given
a blank piece of paper and asked to draw the face of a clock, put in all the numbers, and set the hands to a certain time. The time setting is extremely important; various times are used, but ten after eleven is most common as it is a very sensitive time. In order to draw this time correctly, the ten needs to be recoded to a two.
The clock drawing test is quick and easy to administer, and provides neurologists and other clinicians with a lot of information in a very short time. This simple tool is often used in combination with other screening tests but can provide valuable clues on its own. By examining a person’s clock, you can identify various cognitive impairments — or a lack thereof.
It is relatively easy to train non-professional staff to administer a clock drawing test. In the clinical setting, any healthcare professional who is trained in how to administer the test is able to do so. But, the interpretation is most often done by a physician or neuropsychologist.
Analyzing the clock involves the skill of looking at the process the person uses to draw their clock, and then determining what cognitive functions go into the process. Different types of errors point to different problems with brain functions. The problems most commonly identified using the clock test are executive dysfunctions, such as those used with planning, attention, repetitive behaviours and visuospatial deficits, such as the inability to identify visual and spatial relationships among objects. Some examples are described below:
All 12 numbers on one side of the clock, indicating a planning problem
Clock with all zeros, indicating a language problem (difficulty producing numbers)
Spokes of a wheel clock, indicating perseveration (i.e., repeating an action without stopping — in this example, the interval marks extended to the centre of the clock)
Numbers drawn both inside and outside of the clock, indicating a visuospatial problem
The origins of the clock drawing test are relatively unknown, but it is believed it was developed in the early 1900s. Since the first clinical mention of the test in the early 1950s (i.e., The Parietal Lobes by MacDonald Critchley), the test has since become one of the most widely used cognitive screening instruments in clinical and research settings.
In 1994, Dr. Freedman published a book on clock drawing with a team of multidisciplinary experts. The book, Clock Drawing: A Neuropsychological Analysis, is a practical guide to the assessment of clock drawing, which takes a process-oriented approach to qualitative impairment. Dr. Freedman and his team also largely popularized the time setting for the test as 10 minutes after 11.
At Baycrest, Dr. Freedman and his former fellow, Dr. Eslam Abdellah, are now leading a study, in conjunction with the Temerty Faculty of Medicine at the University of Toronto, which examines the sequencing of drawing a clock. This is to investigate whether the order in which people draw the different elements of the clock has any diagnostic value. This is being conducted with data from the TDRA Memory Clinics Database.