Stepping and tapping: combining motor tasks improves cognitive classification.

Gait and key-tapping are individually associated with mild cognitive impairment (MCI) and dementia. However, it is unclear if these motor functions are correlated, or whether combining them improves classification of objective (dementia, MCI) and subjective cognitive impairment (SCI). We recruited 73 participants with dementia, 106 MCI, 57 SCI, and 83 cognitively healthy controls (HC). Consensus diagnosis was made after gold-standard interdisciplinary assessment. Fast-paced gait was assessed on an electronic walkway and fast-paced key-tapping on a computer keyboard. Correlations between gait and key-tapping measures (speed, frequency, variability and contact) were tested using Pearson's correlation. Classification accuracy was calculated using area under receiver-operating-characteristic curves (AUC) and compared to the null model comprising age, sex and education. Gait and key-tapping measures correlated moderately. Combined gait and key-tapping speed improved classification accuracy of dementia (.97), and MCI (.91), from HC, but not SCI, compared to gait (dementia: .94, MCI: .87) or the null model (dementia: .89, MCI: .79). Gait and key-tapping measures were associated with Alzheimer's disease and vascular dementia, but the effect size for key-tapping variability was larger in vascular dementia (β: 225.71) compared to Alzheimer's disease (β: 38.30). Gait and key-tapping variability was associated with non-amnestic MCI. Measures of gait were correlated with corresponding key-tapping measures, but their association with cognitive impairment was not the same. Combining gait and key-tapping motor measures improved classification accuracy of MCI and dementia. This suggests gait and key-tapping measures provide information about different aspects of motor-cognitive association worth further investigation.