Lap Time Variability From a 400-m Walk Is Associated With Future Mild Cognitive Impairment and Alzheimer's Disease.
Qu Tian, Susan M Resnick, Stephanie A Studenski and 1 others
PMID 31227471WHAT IT FOUND
Older adults later diagnosed with MCI or Alzheimer's disease had a 0.059 m/sec per year greater rise in 400-meter walk lap time variability before symptoms than matched controls.
The best cut-off had 75% sensitivity and 52% specificity.
Key findings
01Older adults later diagnosed with MCI or AD had an annual 0.059 m/sec greater increase in lap time variability before symptom onset than matched controls.
02The greater increase in lap time variability remained after adjustment for baseline gait speed, baseline cognition, and later changes in gait speed.
03The optimal annual change cut-off in lap time variability was 0.4 seconds, with 75% sensitivity and 52% specificity.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The number of MCI/AD cases was modest. Participants in the Baltimore Longitudinal Study of Aging tend to be healthier, more educated, and of higher socioeconomic status than the general population. Some MCI/AD cases had only one lap time variability assessment before symptom onset, which could underestimate the association. Controls had more visits on average than cases. The study could not compare trajectories with non-AD dementia because the sample size was insufficient. It could not test longitudinal step-to-step gait variability because of limited longitudinal data. The 0.4-second cut-off had specificity of 52%. The sample was drawn from a population-based study, not a clinical population.
Declared interests
The study was supported by intramural NIH funding, and the authors declared no conflicts of interest.
The easy way to misread this
Do not treat the 0.4-second annual change as a clinical diagnosis of MCI/AD. The specificity was 52%, and the study was observational.