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Published on: September 28, 2010
Regional Gray Matter Volume Links Rest-Activity Rhythm Fragmentation With Past Cognitive Decline
Stephen F Smagula1, Lana Chahine2, Andrea Metti3
1Department of Psychiatry (SFS, AR, and HJA), School of Medicine, University of Pittsburgh, Pittsburgh, PA.
Objectives:
We examined the extent to which measures of neurodegeneration and cerebrovascular disease explain the rest-activity rhythm (RAR)-cognition link.
Methods:
Seventy participants (mean age at MRI = 86, standard deviation (SD) = 2.6; 53% female) had cognitive, MRI, and accelerometer data. The slope of cognitive decline was defined applying a mixed model to 10 repeated Modified Mini Mental Status Test (3MS) measures over 14 years. Regional gray matter volume (GMV), white matter hyperintensities, and RARs were measured around year 12.
Results:
Past 3MS decline was related to RAR fragmentation (per SD β = -0.43, 95% confidence interval: -0.73, -0.14) and lower posterior parietal GMV (per standard deviation β = 0.47, 95% confidence interval: 0.14, 0.79). Higher RAR fragmentation was related to lower posterior parietal GMV (Pearson r = -0.39, n = 70, p = 0.0007), which attenuated the association of RAR fragmentation and past cognitive decline by 17%.
Conclusions:
Longitudinal studies are warranted to understand the temporal relations and mechanisms linking RAR fragmentation and neurodegeneration.
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Classifying Matter by Composition
According to its composition, the matter can be classified into two broad categories — pure substances and mixtures.
A pure substance is a form of matter that has a constant composition throughout with uniform properties. For example, any sample of sucrose has the same composition and same physical properties, such as melting point, color, and sweetness, regardless of the source from which it is isolated.
A mixture is composed of two or...

