Turning as a single and dual task—associations with alzheimer’s and vascular pathologies in cognitively healthy older people

BACKGROUND: Turning performance is an important and challenging motor activity, with potential relevance in several brain diseases. This study aimed to determine how Alzheimer's and vascular pathologies are associated with turning (360° while standing and 180° while walking) both as a single task and during dual-tasking in cognitively healthy older people. METHODS: Cognitively healthy older people (n = 297, mean age 77.7 years, 61.6% women) were included. A 180° turn was assessed using a wearable sensor; a 360° turn was assessed both clinically and using a sensor. Dual-tasking included a simultaneous subtraction task. Alzheimer's pathologies (Aβ and tau) were assessed using positron emission tomography. Vascular pathology (white matter hyperintensities, WMH) was assessed using magnetic resonance imaging. Logistic and linear regression analyses were used. RESULTS: Aβ and tau pathologies were significantly associated with being unstable while dual-tasking and turning 360°. When including both Aβ and tau in the model, only tau remained significantly associated with being unstable (OR 22.42, 95% CI 1.43, 349.88, p = 0.027). WMH were associated with impaired turning as a single task, i.e., an increased turn duration (360°) and a decreased peak angular velocity (180°: B -1.27, 95% CI -2.33, -0.21], p = 0.018). CONCLUSIONS: This study suggests that early Alzheimer's pathologies are associated with an instability while turning 360° and dual-tasking, whereas WMH seem to be associated with impaired turning as a single task in cognitively healthy older people. Turning assessments seem promising for investigating motor aspects in very early stages of Alzheimer's disease and vascular brain disease.