Less daily computer use is related to smaller hippocampal volumes in dementia-free elderly

Abstract

Unobtrusive continuous in-home monitoring may be a more sensitive means of detecting early functional changes associated with conversion to mild cognitive impairment and dementia in older individuals than traditional testing methods acquired sporadically over time. Twenty-nine dementia-free elderly volunteers (mean age 87.4, MMSE 28.2) enrolled in the Intelligent Systems for Assessing Aging Change study underwent 3T brain MRI. FreeSurfer was used to determine gray matter (GM) and hippocampal volumes. White matter hyperintensities (WMH) were derived using customized software. In-home computer use (CPU) was calculated using daily mouse movement detection and averaged over a one month period surrounding the time of their MRI visit. A multivariate logistic regression was performed with outcome of either high (> 25 min/day) or low (< 25 min/day) average computer use. A voxel based morphometry analysis was also performed to identify relationships between CPU and regional GM density. T1 images were brain extracted and then linearly aligned to the MNI-152 template and averaged to create a study specific template. All T1 images were then non-linearly aligned to this template while the degree of expansion or contraction was calculated. This transform was then applied to segmented GM tissue masks which were modulated by the Jacobian and then used for permutation testing in a model which also accounted for age and gender. In the univariate analysis, less CPU was associated with smaller hippocampal volumes, but not with either total GM or WMH volumes. In a multivariate regression adjusted for age, gender, and intracranial volume, less CPU was associated with smaller hippocampal volume (p = 0.027). Voxel-wise analysis demonstrated that greater CPU was associated with increased GM density in the: right hippocampus, left hippocampus, left lingual gyrus, right inferior temporal gyrus, left superior temporal gyrus and right cingulate gyrus. Daily computer use is related to brain regions linked to memory function and the processing of visual and spatial stimuli, areas previously shown to be associated with conversion to Alzheimer's dementia. Findings support the use of continuous in-home monitoring as a sensitive method to detect meaningful changes in older individuals at risk for dementia. VBM analysis. Colored voxels indicate regions of decreased GM density significantly associated with less daily computer use (p<0.05).