Determinants of visually significant cataract among type 2 diabetes mellitus patients attending a tertiary eye care center in south Ethiopia.

Physical activity (PA) promotes cardiovascular (Kraus et al. ) and neuronal (Domingos et al. ) health, and it has been associated with a decreased risk of neurodegenerative diseases (López‐Ortiz et al. ). In a previous study, we established a link between higher levels of PA and larger gray matter volume (Fox et al. ). Building upon this, evaluating brain structural connectivity could enable a better understanding of the effects of PA on brain organization and function (Won et al. ). White matter (WM) integrity, which is crucial for brain structural connectivity, declines with age (Cox et al. ) and is affected by neurodegenerative diseases (Rosbergen et al. ) as well as by cardiovascular risk (de Groot et al. ). Alterations at the microstructural level often precede macrostructural changes in WM (de Groot et al. ). PA, on the other hand, has been associated with improved macro‐ and microstructural WM integrity (Sexton et al. ; Won et al. ). However, previous studies have been hampered by small sample sizes and self‐reported measures of PA, which are subjective and prone to recall bias. Diffusion‐weighted magnetic resonance imaging (dMRI) allows for measuring the microstructural integrity of WM, which is considered a sensitive marker of cerebrovascular health (de Groot et al. ). The structural boundaries of myelinated axons restrict the diffusion of water molecules so that they are more likely to diffuse along, rather than perpendicular to, healthy WM fibers. Diffusion Tensor Imaging (DTI; Basser et al. ) utilizes these boundaries to derive measures of WM microstructure such as fractional anisotropy (FA) and mean diffusivity (MD). While FA estimates the proportion of diffusion along one WM fiber tract and reflects greater fiber integrity, MD estimates the overall diffusivity and represents a breakdown in fiber integrity. However, DTI measures may not be sufficiently informative in regions of crossing fibers (Timmers et al. ). Neurite orientation and dispersion imaging (NODDI; Zhang et al. ) is a biophysical model which describes diffusivity properties of distinct tissue compartments based on dMRI acquisitions of greater diffusion weighting (higher and multiple ‐values), and attempts to provide more insight into the biological processes underlying microstructural changes through estimation of the neurite density index (NDI), angular variation of fibers (orientation dispersion index, ODI), free water fraction (isotropic volume fraction, ISOVF), and diffusion from the extra‐neurite space (extracellular volume fraction, ECVF; Timmers et al. ).