Abstract
BackgroundPhysical inactivity is one of the modifiable risk factors for hippocampal atrophy and Alzheimer's disease. We investigated the relationship between physical activity, hippocampal atrophy, and memory using structural equation modeling (SEM).Materials and MethodsWe examined 213 community‐dwelling elderly subjects (99 men and 114 women with a mean age of 68.9 years) without dementia or clinically apparent depression. All participants underwent Mini‐Mental State Examination (MMSE) and Rivermead Behavioral Memory Test (RBMT). Physical activities were assessed with a structured questionnaire. We evaluated the degree of hippocampal atrophy (z‐score—referred to as ZAdvance hereafter), using a free software program—the voxel‐based specific regional analysis system for Alzheimer's disease (VSRAD) based on statistical parametric mapping 8 plus Diffeomorphic Anatomical Registration Through an Exponentiated Lie algebra.ResultsRoutine magnetic resonance imaging findings were as follows: silent brain infarction, n = 24 (11.3%); deep white matter lesions, n = 72 (33.8%); periventricular hyperintensities, n = 35 (16.4%); and cerebral microbleeds, n = 14 (6.6%). Path analysis based on SEM indicated that the direct paths from leisure‐time activity to hippocampal atrophy (β = −.18, p < .01) and from hippocampal atrophy to memory dysfunction (RBMT) (β = −.20, p < .01) were significant. Direct paths from “hippocampus” gray matter volume to RBMT and MMSE were highly significant, while direct paths from “whole brain” gray matter volume to RBMT and MMSE were not significant. The presented SEM model fit the data reasonably well.ConclusionBased on the present SEM analysis, we found that hippocampal atrophy was associated with age and leisure‐time physical inactivity, and hippocampal atrophy appeared to cause memory dysfunction, although we are unable to infer a causal or temporal association between hippocampal atrophy and memory dysfunction from the present observational study.
Highlights
Old age is the single greatest risk factor for Alzheimer’s disease (AD); physical inactivity, is one of the strong predictors of incident AD (Beydoun et al, 2014; Yoshitake et al, 1995)
We evaluated the degree of hippocampal atrophy, using a free software program—the voxel-based specific regional analysis system for Alzheimer’s disease (VSRAD) advance version (Matsuda et al, 2012) based on statistical parametric mapping 8 (SPM8) plus Diffeomorphic Anatomical Registration Through an Exponentiated Lie algebra (DARTEL) (Ashburner, 2007; Klein et al, 2009)
This study showed that hippocampal atrophy was associated with age, less education, and leisure-time physical inactivity
Summary
Old age is the single greatest risk factor for Alzheimer’s disease (AD); physical inactivity, is one of the strong predictors of incident AD (Beydoun et al, 2014; Yoshitake et al, 1995). Physical activity is defined as bodily activity that results in energy expenditure above resting levels; exercise refers to physical activity that is structured to meet specific fitness gains (Thomas, Dennis, Bandettini, & Johansen-Berg, 2012). Higher levels of objective measures of total daily physical activity—activity energy expenditure assessed with doubly labeled water (Middleton et al, 2011) or actigraphy (Buchman et al, 2012)—were associated with a reduced risk of cognitive decline or AD. Hippocampal atrophy is the most established structural AD imaging biomarker; structural MRI imaging is the most dynamic— among the major biomarkers of AD—in the prodromal phase of the disease (i.e., mild cognitive impairment [MCI]) (Jack, 2012; Petersen et al, 2009). We examined associations among physical activity, structural MRI findings—gray matter atrophy in the whole brain and in the hippocampus, and memory function in nondemented elderly subjects
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