Cerebral Amyloid-ß Deposition Is Associated with Impaired Gait Speed and Lower Extremity Function.

BACKGROUND: Impaired physical function (i.e., slowing of gait, muscle weakness, and poor mobility) is common in older adults with cognitive impairment and dementia. Evidence suggests that cerebral small vessel disease, specifically white matter lesions (WMLs), is associated with impaired physical function, but little research has been conducted to understand the specific role of Alzheimer's disease pathology in physical outcomes. OBJECTIVE: The objective of this study was to examine the association between cerebral amyloid-ß (Aß) deposition and physical function in people with cognitive impairment. METHODS: Thirty participants completed an 11C Pittsburgh compound B (PIB) position emission tomography (PET) scan to quantify global Aß deposition using standardized uptake value ratio (SUVR). We assessed usual gait speed, muscle strength of the lower extremities, balance, and functional mobility using the Short Physical Performance Battery (SPPB) and the Timed Up and Go Test (TUGT). Multiple linear regression analyses examined the association between Aß and each measure of physical function, adjusting for age, body mass index, and WML load. RESULTS: Global PIB SUVR was significantly associated with usual gait speed (ß= -0.52, p = 0.01) and SPPB performance (ß= -0.47, p = 0.02), such that increased Aß deposition was associated with reduced performance on both measures. Global PIB SUVR was not significantly associated with TUGT performance (ß= 0.32, p = 0.08). CONCLUSIONS: Cerebral Aß deposition is associated with reduced gait speed, muscle strength, and balance in older adults with cognitive impairment independent of WML load. However, Aß deposition was not associated with functional mobility.