Sharp rises in blood sugar after meals may raise Alzheimer’s risk, according to genetic analysis of more than 350,000 adults.

The findings point to after-meal glucose, rather than overall blood sugar, as a possible factor in long-term brain health.

Researchers examined genetic and health data from over 350,000 UK Biobank participants aged 40 to 69, focusing on fasting glucose, insulin, and blood sugar measured two hours after eating.

The team used Mendelian randomisation, a genetic method that helps test whether biological traits may play a direct role in disease risk.

People with higher after-meal glucose had a 69 per cent higher risk of Alzheimer’s disease.

This pattern, known as postprandial hyperglycaemia (elevated blood sugar after eating), stood out as a key factor.

The increased risk was not explained by overall brain shrinkage (atrophy) or white matter damage, suggesting after-meal glucose may affect the brain through other pathways not yet fully understood.

Dr Andrew Mason, lead author, said: “This finding could help shape future prevention strategies, highlighting the importance of managing blood sugar not just overall, but specifically after meals.”

Dr Vicky Garfield, senior author, added: “We first need to replicate these results in other populations and ancestries to confirm the link and better understand the underlying biology.

“If validated, the study could pave the way for new approaches to reduce dementia risk in people with diabetes.”

A recent international study that pooled brain scans and memory tests from thousands of adults has shed new light on how structural brain changes are tied to memory decline as people age.

The findings show that the connection between shrinking brain tissue and declining memory is nonlinear, stronger in older adults, and not solely driven by known Alzheimer’s-associated genes like APOE ε4.

This suggests that brain ageing is more complex than previously thought, and that memory vulnerability reflects broad structural changes across multiple regions, not just isolated pathology.

Alvaro Pascual-Leone, MD, PhD is senior scientist at the Hinda and Arthur Marcus Institute for Aging Research and medical director at the Deanna and Sidney Wolk Center for Memory Health.

The researcher said: “By integrating data across dozens of research cohorts, we now have the most detailed picture yet of how structural changes in the brain unfold with age and how they relate to memory.”

The study found that structural brain change associated with memory decline is widespread, rather than confined to a single region.

While the hippocampus showed the strongest association between volume loss and declining memory performance, many other cortical and subcortical regions also demonstrated significant relationships.

This suggests that cognitive decline in ageing reflects a distributed macrostructural brain vulnerability, rather than deterioration in a few specific brain regions.

The pattern across regions formed a gradient, with the hippocampus at the high end and progressively smaller but still meaningful effects across large portions of the brain.

Importantly, the relationship between regional brain atrophy and memory decline was not only variable across individuals but also highly nonlinear.

Individuals with above-average rates of structural loss experienced disproportionately greater declines in memory, suggesting that once brain shrinkage reaches higher levels, cognitive consequences accelerate rather than progress evenly.

This nonlinear pattern was consistent across multiple brain regions, reinforcing the conclusion that memory decline in cognitively healthy ageing is linked to global and network-level structural changes, with the hippocampus playing a particularly sensitive role but not acting alone.

Pascual-Leone said: “Cognitive decline and memory loss are not simply the consequence of ageing, but manifestations of individual predispositions and age-related processes enabling neurodegenerative processes and diseases.

“These results suggest that memory decline in ageing is not just about one region or one gene — it reflects a broad biological vulnerability in brain structure that accumulates over decades.

“Understanding this can help researchers identify individuals at risk early, and develop more precise and personalized interventions that support cognitive health across the lifespan and prevent cognitive disability.”