Cognitive screening in community-dwelling elders: performance on the clock-in-the-box

Abstract

Background: The Clock-in-the-Box is a rapid (2-minute) cognitive screening tool. The purpose of this study was to compare the Clock-in-the-Box with the Mini-Mental State Exam and neuropsychologic tests; to determine Clock-in-the-Box score normative values by age and education group; and to determine if the Clock-in-the-Box score is associated with measures of physical function.

Methods: Community-dwelling older participants in the Boston area were recruited for a prospective, longitudinal study in which they completed a variety of cognitive and functional assessments.

Results: At baseline, participants (n=798; mean age [± standard deviation]=78.2 [±5.5] years; 14 [±3] mean years of education) completed in-home assessments of cognition (Clock-in-the-Box and Mini-Mental State Exam), measures of independent function (Activities of Daily Living and Instrumental Activities of Daily Living), and measures of physical function (Short Physical Performance Battery). The mean Mini-Mental State Exam score was 27.1 (±1.6; range 0-30 [0 worst]), and the mean Clock-in-the-Box score was 6.2 (±1.6; range 0-8 [0 worst]). Performance on the Clock-in-the-Box was correlated (Spearman) with the Mini-Mental State Exam (r=0.49, P<.001) and neuropsychologic measures (r=0.37-0.50; P<.001). Higher Clock-in-the-Box score was significantly associated with no difficulty in Activities of Daily Living (χ(2) = 39.6, P<.001) and Instrumental Activities of Daily Living (χ(2) = 35.5, P<.001). In addition, higher Clock-in-the-Box scores were associated with higher scores on the Short Physical Performance Battery (F=5.4, P<.001).

Conclusion: The Clock-in-the-Box is a brief cognitive screening test that is correlated with the Mini-Mental State Exam, neuropsychologic tests, and measures of independent and physical function in community-dwelling older adults.

Figure 1. Sample Clock Drawing

The four panels (A, B, C, and D) display Clock-in-the-Box scores of 8, 6, 4, and 2, display. Panel A) represents a Clock-in-the-Box score of 8 because the clock was drawn in the blue box (not shown), the circle is large enough to accommodate the numbers, all numbers are present in the correct order and appropriately spaced, as well as the time is correct with hands originating from near the center. Panel B) represents a clock score of 6, with two points deducted for the incorrect time and completion in an incorrect (yellow) box. Panel C) resembles a clock, is appropriate size to accommodate all of the numbers, was drawn in the blue box, and has appropriate hand origin and length. Points were not given because the number 12 is repeated, the number 3 is not legible, the spacing is not uniform, and the time is incorrect. Panel D) represents a score of 2 because it resembles a clock and was drawn in the correct box. Points were not given for number inclusion, number order (3 is repeated), the numbers are not evenly spaced, the circle is not completed, no time is indicated and no hands are drawn.

Figure 2. Clock-in-the-Box performance and Mini Mental State Examination

The median, 25^th, and 75^th percentile are displayed in the box and the range is displayed with the bars.