Lap Time Variability From a 400-m Walk Is Associated With Future Mild Cognitive Impairment and Alzheimer's Disease

Abstract

ObjectivesTo determine whether the trajectory of preclinical lap time variability from a 400-m walk differentiates participants with future mild cognitive impairment (MCI)/Alzheimer's disease (AD) from matched controls. DesignA case-control retrospective study embedded in a large longitudinal cohort study, the Baltimore Longitudinal Study of Aging (BLSA). SettingIn the BLSA, participants were scheduled for clinical visits, including mobility and cognitive assessments. Data reported here were collected between April 2007 and September 2017 (average follow-up 5.2 ± 2.4 years). Participants67 participants developed MCI/AD and 134 age- and sex-matched controls remained cognitively normal. MeasurementsDiagnoses of MCI and AD were adjudicated at a consensus conference. The rate of change in lap time variability between MCI/AD cases prior to symptom onset and controls were compared using mixed effects linear regression, and adjusted for baseline executive function, memory, gait speed, and changes in gait speed. ResultsCompared to controls, eventual MCI/AD cases had a greater rate of increase in lap time variability prior to symptom onset (β = 0.59, P = .009). This association was independent of baseline cognition, gait speeds at baseline or change over time from a 6-m or 400-m walk. Conclusion/ImplicationsIndependent of other early indicators and gait slowing, a greater rate of increase in lap time variability from a 400-m walk differentiates individuals who eventually develop MCI/AD from controls, suggesting that early pathology affects the automaticity of walking. Lap time variability can be assessed during routine clinical practice over time and might help identify individuals at risk for future MCI/AD.