Hand motor function of patients with early- and late-onset Alzheimer's disease and its relation to activities of daily living.

Background: Alzheimer's disease (AD) is the most common cause of dementia, characterized by a progressive deterioration of cognitive capacity and the ability to carry out activities of daily living (ADL). Hand motor function may also be impaired, with slower and less automated movements during fine motor tasks. The severity of impairments may depend on task characteristics and the age of onset of AD. Objective: This study investigated hand motor function of persons with dementia due to AD during handwriting and sequential hand movements, focusing on the impact of task complexity and age at onset. Methods: Kinematic analysis of handwriting and sequential hand movements was carried out in 24 AD patients (early-onset AD (EOAD): n = 13; late-onset AD (LOAD): n = 11) and 23 controls (≤ 65 years: n = 12; > 65 years: n = 11). To estimate the impact on patients' ADL performance, the Jebsen-Taylor Hand Function Test (JTHFT) was administered. Results: AD patients exhibited a significantly lower handwriting and sequencing performance compared to healthy controls. Complexity effects were detectable for handwriting and sequencing; for z-standardized sequencing frequency, they were more prominent in AD patients than controls. Age at onset had no effect on handwriting or sequential hand movements; however, handwriting and sequencing frequency were predictive of JTHFT performance in EOAD, but not in LOAD. Conclusions: Kinematic measures of both handwriting and sequential hand movements were able to capture impairments in AD patients. Deteriorations of frequencies seem to translate into deficits in simulated ADL performance only in EOAD.