Associations between modifiable risk factors and white matter of the aging brain: insights from diffusion tensor imaging studies

Thomas M Wassenaar,Kristine Yaffe,Ysbrand D Van Der Werf,Claire E Sexton

doi:10.1016/j.neurobiolaging.2019.04.006

Abstract

There is increasing interest in factors that may modulate white matter (WM) breakdown and, consequentially, age-related cognitive and behavioral deficits. Recent diffusion tensor imaging studies have examined the relationship of such factors with WM microstructure. This review summarizes the evidence regarding the relationship between WM microstructure and recognized modifiable factors, including hearing loss, hypertension, diabetes, obesity, smoking, depressive symptoms, physical (in) activity, and social isolation, as well as sleep disturbances, diet, cognitive training, and meditation. Current cross-sectional evidence suggests a clear link between loss of WM integrity (lower fractional anisotropy and higher mean diffusivity) and hypertension, obesity, diabetes, and smoking; a relationship that seems to hold for hearing loss, social isolation, depressive symptoms, and sleep disturbances. Physical activity, cognitive training, diet, and meditation, on the other hand, may protect WM with aging. Preliminary evidence from cross-sectional studies of treated risk factors suggests that modification of factors could slow down negative effects on WM microstructure. Careful intervention studies are needed for this literature to contribute to public health initiatives going forward.

Highlights

White matter (WM) pathways play an essential role in the human brain by connecting distributed regions and enabling efficient exchange of information
We focus on evidence from diffusion tensor imaging (DTI) studies that have examined modifiable factors proposed to alter the brain’s WM microstructure during aging
One such study reported that higher Mediterranean diet adherence in older adults was associated with a pattern of preserved WM integrity, reflected by higher fractional anisotropy (FA) and lower diffusivity (MD, RD, AxD) in widespread WM areas, including the corpus callosum, anterior and posterior thalamic radiations and inferior fronto-occipital fasciculus (Pelletier et al, 2015)

Summary

Introduction

White matter (WM) pathways play an essential role in the human brain by connecting distributed regions and enabling efficient exchange of information. WM is crucial for efficient cognitive functioning (Filley and Fields, 2016), and changes in its make-up shape human behavior and underlie learning (Zatorre et al, 2012). WM decline further increases risk of various brain disorders (Fig. 1) and is a feature of several dementias (Debette and Markus, 2010; Filley and Fields, 2016; Prins and Scheltens, 2015). WM disruption, including myelin loss and oligodendrocyte dysfunction, may be among the earliest pathological changes in AD, has been related to AD-related cognitive deficits, and could be considered as a target for early treatment (Nasrabady et al, 2018). WM of the adult brain demonstrates plasticity, with structural changes including myelin formation and remodeling occurring over hours, days, weeks, and months (Sampaio-Baptista and Johansen-Berg, 2017)

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Discussion

Conclusion