Hand Motor Dysfunction Is Associated with Both Subjective and Objective Cognitive Impairment across the Dementia Continuum.

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.