PPubMed9 Jul 2025

Habit-learning and decision-making circuits are susceptible to glycemic variability in type 2 diabetes: a longitudinal study

Carolina Moreno, Otília C. d’Almeida, Joana Crisóstomo, Nádia Canário, Leonor Gomes, Miguel Castelo-Branco

Abstract

1## Introduction Diabetes mellitus is associated with various changes in brain function and structure (). Brain atrophy, characterized by lower total and regional gray matter (GM) volumes, has consistently been reported in patients with type 2 diabetes (T2DM), particularly among older adults with cognitive dysfunction (). With the global epidemic of T2DM and the growing aging population (), a focus on diabetes brain health might have an additional impact on delaying or even preventing diabetes-related mental health conditions. Previous longitudinal studies have shown relatively homogeneous res

A figure from Habit-learning and decision-making circuits are susceptible to glycemic variability in type 2 diabetes: a longitudinal study — fig. from the paper

§ The Valyu brief

The paper, in five minutes

Read from the full text via Valyu Contents

In type 2 diabetes, higher glycemic variability predicts region-specific gray matter loss over 7 years, especially in the temporal lobe, with each 1 mmol/L rise in MAGE causing ~1.2% extra atrophy.

What’s new

i.Identified region‑specific susceptibility of gray matter to glycemic variability in T2DM
ii.Performed a 7‑year longitudinal MRI study linking GV metrics to brain atrophy
iii.Applied the FreeSurfer 7 longitudinal pipeline for detailed cortical, subcortical and hippocampal subfield analysis
iv.Quantified the impact of MAGE on temporal lobe atrophy (1.2% per 1 mmol/L increase)
v.Demonstrated strong negative correlations between GV and habit‑learning/decision‑making circuits

How they did it

A cohort of 170 participants (85 with T2DM) underwent baseline clinical, biochemical and 3 T MRI assessments; 29 (15 with T2DM) were re‑examined after 7.1 ± 0.7 years. Glycemic variability metrics (SD, M‑value, MAG, MAGE, CoV) were calculated from 7‑point glucose sampling, and regional gray matter volumes were measured using the FreeSurfer 7 longitudinal pipeline.

What they found

Negative correlations between MAGE and gray matter SPC: temporal lobe r=-0.63 (p=0.021), insula ρ=-0.62 (p=0.022), thalamus r=-0.64 (p=0.024), hippocampus r=-0.59 (p=0.034), putamen ρ=-0.65 (p=0.017)
Presubiculum volume correlated with MAGE (r=-0.73, p=0.005)
Linear regression: each 1 mmol/L increase in MAGE reduces temporal lobe SPC by 1.2% on average
Baseline sample: 85 T2DM; follow‑up: 15 T2DM after ~7 years

Caveats

✕Small longitudinal sample (15 T2DM participants) limits statistical power
✕Loss to follow‑up due to COVID‑19 and other factors
✕Glycemic variability measured with intermittent 7‑point sampling rather than continuous glucose monitoring
✕Potential insufficient power to detect group differences in overall GM atrophy

in plain words

People with type 2 diabetes who have big swings in their blood sugar tend to lose brain tissue in certain areas over several years. The study showed that more variability, measured by a number called MAGE, was linked to about 1% more shrinkage in the temporal lobe for each extra unit of variability. This suggests that keeping blood sugar steady could protect parts of the brain that help us learn habits and make decisions.

why it matters

The findings suggest that glycemic variability is a modifiable risk factor for brain atrophy in diabetes, linking metabolic control to neural circuits underlying habit learning and decision making, which has implications for clinical management of T2DM beyond glucose level targets.

Follow the thread

type 2 diabetes glycemic variability brain atrophy MRI longitudinal study habit-learning circuits

§ The Valyu brief

Reading the full paper and taking notes. This takes a few seconds…

§ Ask this paper

Ask a question about this paper

Valyu reads the full text and answers from what the paper actually says.

§ Related work in other archives

Habit-learning and decision-making circuits are susceptible to glycemic variability in type 2 diabetes: a longitudinal study

The paper, in five minutes

Ask a question about this paper

Similar papers in all four archives

Similar papers in all four archives

The paper, in five minutes