Clock‐drawing center estimation varies with age and Alzheimer's disease

Abstract

AbstractBackgroundHealthy, young adults deviate leftward when bisecting horizontal lines and upward when bisecting vertical lines, a phenomenon termed “pseudoneglect”. With aging, there is a reduction in this leftward bias. Alzheimer’s disease (AD) can be associated with neglect. Our research assessed directional bias in healthy controls, patients with amnestic mild cognitive impairment (aMCI), and AD with the digital Clock Drawing Test (dCDT) command test condition.MethodThe sample included 68 cognitively normal older adults (M= 72.08, SD= 5.1), 16 younger healthy adults (M= 31.34, SD= 5.83), 13 patients with aMCI (M= 72.56, SD= 6.00), and 24 patients with AD (M= 80.34, SD= 5.97). dCDT protocols were selected for correct number placement within 30 degrees of ideal and hands directed toward the correct digits. The estimated center of the clock face was determined by the point where clock hands converged. Horizontal and vertical deviations of this estimated center from the actual center in each group were normalized as percentages of the clock face diameter.ResultHorizontal deviation: Younger adults deviated leftward(M= 3.55%, SD = 2.82%) and differed from older controls (p= 0.003) who were near center with leftward deviation (0.31%, SD 2.58%). AD patients deviated leftward (M= 3.77%, SD = 4.58%) relative to older controls (p= 0.008). aMCI patients also deviated leftward (M= 2.18%, SD=2.36%) and differed from older controls (p= 0.047).Vertical deviation: Every group deviated upward relative to center (M= 1.82%, SD= 5.09%; p< 0.001).ConclusionOn average, clock center estimation deviates upward similarly across age and AD related neurodegeneration. Leftward “pseudoneglect” was present in younger clocks and decreased with age. AD and aMCI were associated with greater leftward deviation compared to healthy older adults. Leftward deviation on the dCDT may be a useful marker predicting cognitive impairment in otherwise “normal” clocks.