http://www.neurology.org/content/78/24/1946
Abstract
Objective: To determine whether unobtrusive long-term in-home assessment of walking speed and its variability can distinguish those
with mild cognitive impairment (MCI) from those with intact cognition.
Methods: Walking
speed was assessed using passive infrared sensors fixed in series on the
ceiling of the homes of elderly individuals
participating in the Intelligent Systems for
Assessing Aging Change (ISAAC) cohort study. Latent trajectory models
were used
to analyze weekly mean speed and walking speed
variability (coefficient of variation [COV]).
Results: ISAAC
participants living alone included 54 participants with intact
cognition, 31 participants with nonamnestic MCI (naMCI),
and 8 participants with amnestic MCI at
baseline, with a mean follow-up of 2.6 ± 1.0 years. Trajectory models
identified 3
distinct trajectories (fast, moderate, and slow)
of mean weekly walking speed. Participants with naMCI were more likely
to
be in the slow speed group than in the fast (p = 0.01) or moderate (p
= 0.04) speed groups. For COV, 4 distinct trajectories were identified:
group 1, the highest baseline and increasing COV
followed by a sharply declining COV; groups 2
and 3, relatively stable COV; and group 4, the lowest baseline and
decreasing
COV. Participants with naMCI were more likely to
be members of either highest or lowest baseline COV groups (groups 1 or
4),
possibly representing the trajectory of walking
speed variability for early- and late-stage MCI, respectively.
Conclusion: Walking speed and its daily variability may be an early marker of the development of MCI. These and other real-time measures
of function may offer novel ways of detecting transition phases leading to dementia.
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