Metabolic syndrome is associated with accelerated brain aging

Dove, A., Wang, J., Yang, R., Sakakibara, S., Arvanitakis, Z., Schneider, A. L. C., Gottesman, R. F., & Xu, W. (2026). Metabolic syndrome is associated with accelerated brain aging. Alzheimer's & dementia : the journal of the Alzheimer's Association, 22(7), e71563. https://doi.org/10.1002/alz.71563

For today’s Journal Club, we are taking a slightly different angle.

I will be the first to admit that neurodegenerative disorders—conditions such as dementia—are not really my forte. Perhaps I become a little too anxious about missing something, or perhaps the field has simply never quite clicked for me. It is also an extraordinarily complex and challenging area of medicine, so I have enormous respect for the clinicians and researchers who work in it.

This article, however, caught my attention.

The study was published recently, involved a large sample, and appeared in a reputable journal. It also involved an impressive international collaboration, with researchers from countries including Sweden, China and the United States. Importantly, from a funding perspective, the study appears to have been supported through research grants, without pharmaceutical company sponsorship.

So, what were Dove and colleagues investigating?

Metabolic syndrome is one of those conditions many of us are familiar with, even if we do not always recognise it as a defined syndrome. A GP once described it to me as a “disease of prosperity”. That description is certainly debatable, but it does reflect the observation that metabolic syndrome has become increasingly common in many modern societies.

Broadly speaking, metabolic syndrome refers to a cluster of interconnected risk factors, including central obesity, particularly increased abdominal fat, high blood pressure, abnormal cholesterol or triglyceride levels, and elevated blood glucose or insulin resistance. Together, these factors increase the risk of conditions such as type 2 diabetes and cardiovascular disease.

Metabolic syndrome is estimated to affect a substantial proportion of the global population, although its prevalence varies considerably between countries, age groups and demographic populations. I recently travelled to Italy and felt that I saw less obvious metabolic illness there. Of course, that was hardly a scientific observation, and Italy also has its own complicated relationship with appearance, thinness and body-image culture, so there are certainly other issues at play.

The authors begin by discussing evidence that metabolic syndrome may also be associated with poorer brain health. Previous imaging studies have suggested links between metabolic dysfunction and changes in brain structure, including reduced volume in some regions. They then introduce the concept of brain age.

Brain age is an estimate of how old a person’s brain appears on imaging, based on patterns identified using MRI scans and statistical or machine-learning models. This estimated brain age can then be compared with the person’s actual chronological age. The difference is called the brain age gap. For example, if someone is 50 years old but their brain imaging more closely resembles that of an average 60-year-old, they would have a positive brain age gap of approximately 10 years. A larger positive brain age gap may indicate accelerated brain ageing, although it is important to remember that brain age is a research measure rather than a diagnosis in itself. The researchers wanted to determine whether metabolic syndrome was associated with an increased brain age gap and, if so, explore some of the biological mechanisms that might help explain that relationship.

To investigate this, they used data from the famous UK Biobank. The UK Biobank is a long-running research project involving approximately half a million people from across the United Kingdom. Participants were recruited between the ages of 40 and 69 and completed a wide range of assessments, including questionnaires, cognitive testing, physical measurements, lifestyle assessments and blood tests. A proportion of participants later underwent MRI brain imaging. In other words, much of the information was already available. It simply required a group of very intelligent researchers to ask the right question and work out how the data could be used to answer it.

Firstly, the study was enormous: approximately 27,000 participants were included in the analysis. That is a very substantial sample. The statistical analysis is complex, and this is probably the point at which many lay readers—and honestly, me on a tired day—might begin to lose the thread. For me, one of the clearest summaries appears in Figure 1. The figure shows that the brain age gap generally increased alongside metabolic risk factors such as greater waist circumference, higher blood pressure, abnormal lipid levels and markers of diabetes. In simple terms, people with greater metabolic dysfunction tended to have brains that appeared older on MRI than would be expected for their chronological age.

That is an important finding.

I will also be honest: the paper contains a large number of figures, graphs and statistical models, and some are fairly overwhelming. Figure 6 almost resembles a piece of modern art. The researchers also explored biomarkers that may mediate the relationship between metabolic syndrome and brain ageing. “Mediation” refers to a possible pathway through which one factor may influence another. In this case, the researchers examined whether particular biological markers associated with metabolic syndrome might partly explain why the brains of affected participants appeared older. This almost felt like a separate study within the main study.

Although the biomarker findings are interesting, we can probably pause that discussion for today. The central message is that metabolic syndrome may be linked to biological processes, including inflammation, altered metabolism and vascular dysfunction, that could also affect the brain. However, these findings show associations and possible pathways. They do not prove that any one particular biomarker directly causes accelerated brain ageing.

The authors appropriately discussed several limitations. One important concern is that UK Biobank participants are generally healthier, wealthier and more highly educated than the broader population. This means the sample does not fully represent the range of patients we see in everyday clinical practice. The subgroup of participants who completed both blood testing and brain imaging may have been even less representative and less diverse.

In one sense, however, that makes the findings particularly concerning. If an association between metabolic syndrome and accelerated brain ageing can be identified in a comparatively healthy and advantaged sample, the relationship may be at least as important, if not more important, in populations experiencing greater medical and socioeconomic disadvantage.

Another major question is causality: what came first?

The study cannot establish that metabolic syndrome directly causes accelerated brain ageing. It is also possible that changes in brain health contribute to metabolic difficulties, perhaps through effects on motivation, appetite, impulse control, physical activity or the ability to manage chronic illness. The relationship is therefore likely to be complex and bidirectional.

Overall, this large study suggests that metabolic syndrome is associated with brains that appear older on MRI than expected for a person’s chronological age. That finding could have substantial long-term implications.

For me, the study reinforces the importance of holistic, metabolically informed psychiatric care. Psychiatry cannot focus only on symptoms, diagnoses and medications while treating blood pressure, weight, cholesterol and diabetes risk as someone else’s problem. These factors may affect cardiovascular health, functioning and life expectancy, and they may also be relevant to long-term brain health.

This means regularly monitoring blood pressure, weight, waist circumference, glucose and lipid levels. It also means considering the metabolic effects of psychotropic medication, supporting physical activity and nutrition, and ensuring patients receive appropriate primary-care and specialist follow-up.

We may not yet know whether improving metabolic syndrome can directly reverse or prevent accelerated brain ageing. However, this study provides another compelling reason to take metabolic health seriously.

Looking after the body may also be one of the most important ways we look after the brain.