The Association Between Decline in Physical Functioning and Atrophy of Medial Temporal Areas in Community-Dwelling Older Adults With Amnestic and Nonamnestic Mild Cognitive Impairment

Objective: To examine whether declining performance in aspects of physical functioning, including lower extremity muscle strength, 1-legged balance, walking speed, and exercise capacity, is associated with atrophy of medial temporal areas in community-dwelling older adults with mild cognitive impairment (MCI). Design: Cross-sectional study. Setting: General community in Japan. Participants: Community-dwelling older adults 65 years and older with a Clinical Dementia Rating of 0.5 or memory complaints were enrolled in this study. This study examined 34 participants with amnestic MCI (aMCI) and 58 nonamnestic MCI (non-aMCI) participants. Interventions: Not applicable. Main Outcome Measures: The following physical performance tests were conducted: muscle strength of knee extension, 1-legged standing time, 5-m walking test, and 6-minute walk test (6MWT). The z scores of the voxel-based specific regional analysis system for Alzheimer's disease were determined to assess the degree of atrophy in the bilateral medial temporal areas including the entorhinal cortex (MTA-ERC). Results: In the aMCI group, 6MWT performance was associated with MTA-ERC atrophy (beta=-.462, P=.014) after controlling for age. In the stepwise multiple regression analyses, 6MWT and body mass index were found to be significant determinants of MTA-ERC atrophy in all participants (R-2=.275), as well as the aMCI and non-aMCI groups when analyzed separately (R-2=.418 and R-2=.216, respectively). Conclusions: A decline in exercise capacity was found to be more closely associated with atrophy of the MTA-ERC compared with other aspects of physical functioning in older adults with MCI, especially the amnestic type. These findings suggest that it is important for future studies to investigate the effects of increased aerobic activity and improved fitness on brain volume in older adults at risk of developing dementia.