Abstract
Introduction: Motor dysfunction is an important feature of early-stage dementia. Gait provides a non-invasive biomarker across the dementia continuum. Gait speed and rhythm aid risk stratification of incident dementia in subjective cognitive impairment (SCI) and are associated with cognitive domains in mild cognitive impairment (MCI) and dementia. However, hand movement analysis, which may be more accessible, has never been undertaken in SCI and rarely in MCI or dementia. We aimed to address this gap and improve understanding of hand motor-cognitive associations across the dementia continuum. Methods: A total of 208 participants were recruited: 50 with dementia, 58 MCI, 40 SCI, and 60 healthy controls. Consensus diagnoses were made after comprehensive gold-standard assessments. A computer key-tapping test measured frequency, dwell-time, rhythm, errors, and speed. Associations between key-tapping and cognitive domains and diagnoses were analysed using regression. Classification accuracy was measured using area under receiver operating characteristic curves. Results: Hand frequency and speed were associated with memory and executive domains (p ≤ 0.001). Non-dominant hand rhythm was associated with all cognitive domains. Frequency, rhythm, and speed were associated with SCI, MCI, and dementia. Frequency and speed classified ≥94% of dementia and ≥88% of MCI from controls. Rhythm of the non-dominant hand classified ≥86% of dementia and MCI and 69% of SCI. Conclusion: Our findings show hand motor dysfunction occurs across the dementia continuum and, similar to gait, is associated with executive and memory domains and with cognitive diagnoses. Key-tapping performance differentiated dementia and MCI from healthy controls. More research is required before recommending key-tapping as a non-invasive motor biomarker of cognitive impairment.
Plain Language Summary
Dementia affects motor function as well as memory and cognition. It causes subtle changes in the brain that accumulate over many years, affecting the speed and rhythm of movements before manifesting as cognitive impairment. Detecting these dementia-related changes in movement can aid in detecting those who may be at risk of developing dementia in the future. To understand the dementia-related changes in hand movements, we invited a group of participants from patients attending a cognitive clinic. All patients underwent a comprehensive clinical assessment. We also invited a group of healthy participants for comparison. A simple 60 s online computer key-tapping test was used to test hand movement. We examined features of key-tapping performance including frequency, speed, number of incorrect taps, and rhythm. Clinic participants were grouped by diagnosis as subjective cognitive impairment, mild cognitive impairment, and dementia. Key-tapping performance of each group was compared with the healthy participants’ performance. We found that key-tapping performance declines progressively with the increase in severity of cognitive impairment, with the dementia group having the most impaired key-tapping performance. Using the hand movement test, we correctly identified more than 80% of patients with mild cognitive impairment and dementia from the healthy group. The computer key-tapping test is simple, quick, and can be accessed online. It has the potential to be used as a screening tool for people with cognitive symptoms.
