Effect of education on the clock-drawing dementia screen in non-demented elderly persons

J Am Geriatr Soc. 1993 Mar;41(3):249-52. doi: 10.1111/j.1532-5415.1993.tb06701.x.

Abstract

Objective: To examine the effect of education on clock-drawing ability in non-demented elderly persons.

Design, setting, participants: Descriptive study of 187 elderly persons, 77 demented, 110 non-demented, 54 with 9+ years of education, 133 with 8 or fewer years of education, from three university medical center geriatric divisions.

Measurements: Subjects took the Folstein Mini-Mental State Exam and were asked to draw a clock showing a time of 3 o'clock. Clocks were scored using three previously described scoring scales (Shulman, Sunderland, and Wolf-Klein). Mean scores and proportions of normal and abnormal clocks were compared for well and poorly educated non-demented subjects. Sensitivities and specificities for detecting dementia were calculated.

Results: Mean scores of the well educated non-demented subjects were significantly better than mean scores of the poorly educated non-demented subjects on all three scales. However, proportions of abnormal clocks were not significantly different between well and poorly educated on the Wolf-Klein scale. For the poorly educated subgroup, sensitivity and specificity for detecting dementia by clock drawing were 90% and 42% by the Shulman scale, 74% and 44% by the Sunderland scale, and 48% and 90% by the Wolf-Klein scale.

Conclusions: Clock-drawing ability is affected by education in non-demented elderly persons. The scoring method of Wolf-Klein is least educationally affected and maximizes specificity for detecting dementia but has low sensitivity. Educational effects make clock drawing a poor single screening test for dementia in a poorly educated population.

MeSH terms

  • Aged / psychology*
  • Dementia / diagnosis
  • Dementia / psychology
  • Educational Status*
  • Female
  • Humans
  • Male
  • Mental Status Schedule
  • Neuropsychological Tests*
  • Observer Variation
  • Sensitivity and Specificity