Influence of Executive Function on Locomotor Function: Divided Attention Increases Gait Variability in Alzheimer's Disease

Authors

  • Pamela L. Sheridan MD,

    1. From the Behavioral Neurology Division, Department of Neurology,
    2. Gerontology Division, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
    3. Division on Aging, Harvard Medical School, Boston, Massachusetts
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  • Judi Solomont Mat,

    1. Gerontology Division, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
    2. Division on Aging, Harvard Medical School, Boston, Massachusetts
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  • Neil Kowall MD,

    1. Geriatric Research, Education and Clinical Center, Bedford Veterans Affairs Medical Center, Bedford, Massachusetts
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  • Jeffrey M. Hausdorff PhD

    1. Gerontology Division, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
    2. Division on Aging, Harvard Medical School, Boston, Massachusetts
    3. Movement Disorders Unit, Tel Aviv Sourasky Medical Center, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.
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  • This work was supported in part by National Institutes of Health Grants AG-14100, RR-13622, HD-39838, and AG-08812. Dr. Sheridan is a fellow in the Clinical Investigator Training Program, Beth Israel Deaconess Medical Center-Harvard/MIT Health Sciences and Technology, in collaboration with Pfizer, Inc. This work was presented in part at the American Geriatrics Society Annual Meeting, May 2002, Washington, DC.

Address correspondence to Pamela Sheridan, MD, Behavioral Neurology, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215. E-mail: psherida@caregroup.harvard.edu

Abstract

Objectives: To evaluate how cognitive function and divided attention affect gait in Alzheimer's disease (AD).

Design: Cross-sectional intervention study with subjects serving as their own controls.

Setting: Inpatient unit and outpatient clinic for patients with dementia located at a Veterans Affairs Medical Center.

Participants: Twenty-eight patients diagnosed with probable AD.

Intervention: Performance of a cognitive task (repeating random digits) while walking.

Measurements: Neuropsychological measures includ-ing clock drawing, verbal fluency, and digit span were obtained along with the Clinical Dementia Rating and Mini-Mental State Examination, the measures of dementia severity. Gait speed and stride-to-stride variability of gait rhythm were measured, once during normal walking and once during dual-task walking.

Results: During usual walking, subjects walked slowly and with greater gait variability than older adults without AD. Gait speed was significantly reduced (P<.012) and gait variability increased with dual-task walking (P<.007). The effect on gait variability was larger than the effect on gait speed (P<.015). Executive and neuropsychological function were significantly (P<.02) associated with the increased gait variability that occurred when walking with divided attention but not with gait speed or usual, single-task walking measures of gait.

Conclusion: Divided attention markedly impairs the ability of patients with AD to regulate the stride-to-stride variations in gait timing. This susceptibility to distraction and its effect on stride time variability, a measure of gait unsteadiness, could partially explain the predilection to falling observed in patients with dementia. The results also support the concept that persons with AD have significant impairments in the cognitive domain of attention and that locomotor function relies upon cognitive, especially executive, function.

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