A new study reveals that triglyceride–glucose indices and waist-to-height ratio may identify seniors at risk of cognitive deterioration by detecting subtle white matter changes, highlighting a potential biological pathway from insulin resistance to brain ageing.
The triglyceride–glucose index and a related measure that adds waist-to-height ratio may help identify older adults at higher risk of cognitive decline through subtle changes in white matter, according to a new study in Frontiers in Neuroscience. The research, based on data from the Health and Aging Brain Study–Health Disparities cohort, found statistical links between these metabolic markers and performance in several thinking domains, with white matter radial diffusivity appearing to sit on the pathway between the two.
The strongest signals were seen for processing speed and executive function, two abilities that often weaken with age and are closely tied to the brain’s white matter networks. In the study, higher triglyceride–glucose values and higher triglyceride–glucose-to-waist-to-height ratio scores were associated with poorer cognitive scores, and the same indices were linked to radial diffusivity in several tracts, especially the right cingulum and the right superior corona radiata. The authors said these patterns suggest a possible biological route from insulin resistance-related metabolic burden to cognitive ageing.
The analysis drew on 2,606 participants for the cross-sectional work, with 788 people followed for a second cognitive assessment a median of just over two years later. The team used diffusion tensor imaging, a form of MRI that tracks how water moves through brain tissue, to examine 32 white matter tracts. Radial diffusivity, the key measure in the study, reflects water movement perpendicular to nerve fibres and is often interpreted as a marker that may be sensitive to myelin-related change, although it is not specific to any one type of brain injury.
Overall, the study identified 14 candidate indirect pathways in the baseline analysis, all involving radial diffusivity rather than axial diffusivity. Eleven of those pathways had uncertainty intervals that did not cross zero, but the authors also stressed that the findings were not especially stable when the analysis was repeated across bootstrap samples, and that some associations weakened after accounting for white matter hyperintensity burden and other time-varying factors. In the follow-up analysis, five pathways remained linked to later change in cognition, again concentrated in processing speed and executive function.
The results add to a growing body of evidence suggesting that insulin resistance and related metabolic stress may affect the brain well before dementia is diagnosed. They also fit with earlier population studies that have tied insulin resistance and triglyceride–glucose-based measures to poorer white matter integrity and worse cognitive performance. But the authors cautioned that their findings should be read as statistical associations rather than proof of cause and effect, and said independent cohorts with longer follow-up will be needed to test whether the same pathways appear elsewhere.
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