The Effects of Time on ‘Drawing’ Time: A Longitudinal Study of the Clock Drawing Test

Wall Clock, by Ikescs, Creative Commons 3.0 Unported License

There is a 2011 paper in the Journal of Dementia and Geriatric Cognitive Disorders Extra by Paganini-Hill and Clark. The researchers were interested in how people perform on a clock-drawing test as they get older. They looked at a cohort in the Leisure World Cohort Study. This cohort consisted of 4842 people with a mean age of 80 years who were asked to draw a clock in a test that was mailed to them. 1521 people completed the test in 1992 and 1998 and the researchers looked at the results in this subgroup. The researchers were interested in several questions. One of these questions was whether performance on this test deteriorated with age. The people that didn’t complete the test were more likely to have comorbid medical illnesses, to be taking medication and to do less exercise. Thus on a number of measures the group completing the test appeared to have better physical health although even this simple statement may be too broad a generalisation. I won’t go into the details of the test and the scoring methods but will just focus on the results. The researchers were interested in the percentage of participants that were able to correctly perform the clock drawing test.

Essentially they found that for each 5 year increment in age from <75 to >90 there was a corresponding decrease in the percentage of people who correctly drew the clock. Scores on the test lay along a continuum, but correct drawing implied full marks on the test. However what I found interesting was that when scores were compared 6 years later for the same person, scores improved, sometimes worsened or remained stable on average. What this might mean is that people had become used to the test although one test every 6 years seems infrequent*. Another possibility is that there are differences among the participants within these 5 year bandings. There was another interesting feature of the test which was the completion of a mailed test. Therefore it was entirely possible that participants were taking as long as necessary to complete the test and time (no pun intended) was not a constraint.

On one hand therefore there was a deterioration in performance when comparing progressive 5 year bandings of subjects. However there was actually an improvement in the second testing for the same subjects in the 3 youngest age bandings which did not hold for the two oldest bandings. These are interesting results which may tell us about learning on cognitive tests. These results though were subtle. There were also interesting results for people with dementia compared to controls.

* if there was learning it seemed to occur for the younger age-groups and the effect was lost in the two oldest age groups.

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