Apraxic deficits predict general cognitive impairment in patients with biomarker-verified Alzheimer's pathology

Apraxia represents a core feature of Alzheimer's disease (AD), a neurodegenerative disorder characterised by the accumulation of β-amyloid plaques and tau deposition. However, systematic descriptions of apraxic deficits in AD patients remain scarce. Here, we comprehensively investigate apraxia profiles and their link with cognitive impairment in patients with biomarker-verified Alzheimer's pathology. We characterised the frequency and patterns of apraxic deficits in patients with biomarker-verified Alzheimer's pathology using a battery of standardised apraxia tests. Demographic variables and apraxia scores were related to patients' general cognitive impairment using hierarchical regression analysis. Apraxic deficits were found in 67% of patients with biomarker-verified Alzheimer's pathology (n = 63). Patients with Alzheimer's pathology were more impaired in imitating finger gestures (than hand gestures: 89.2% vs. 80.0%, p < 0.001) and imitating complex hand movements (than single hand movements: 97.4% vs. 78.5%, p < 0.001), even when controlling for general cognitive impairment. Apraxia assessments explained about 60% of the variance in dementia severity, with performance in the KAS subtest of pantomiming object use (beta coefficient: 0.47, p = 0.001) and the DATE subtest for limb apraxia (beta coefficient: 0.37, p = 0.005) constituting significant predictors of general cognitive impairment. These findings emphasise the relevance of apraxia in patients with biomarker-verified Alzheimer's pathology, revealing that praxis deficits predict general cognitive impairment in AD. Further research is warranted into the role of apraxia as a potential early diagnostic criterion in AD.