A new study finds that obesity and high blood pressure may directly cause dementia, not just increase the risk.
People living with obesity and high blood pressure may have a greater chance of developing dementia, according to new research published today (January 22) in The Journal of Clinical Endocrinology & Metabolism.
Dementia remains a growing global health concern, and there is currently no cure. The condition causes a serious decline in mental abilities, including memory, reasoning, and thinking skills, which can interfere with daily life.
Understanding Dementia and Its Most Common Forms
Dementia is not a single disease but a group of conditions that progressively damage brain cells. The most common types include Alzheimer’s disease, vascular dementia, and mixed dementia. Over time, nerve cell damage worsens, leading to problems with memory, language, decision-making, and behavior.
Study Finds Direct Causes, Not Just Associations
“In this study, we found high body mass index (BMI) and high blood pressure are direct causes of dementia,” said study author Ruth Frikke-Schmidt, M.D., Ph.D., Professor and Chief Physician at Copenhagen University Hospital – Rigshospitalet and the University of Copenhagen in Copenhagen, Denmark. “The treatment and prevention of elevated BMI and high blood pressure represent an unexploited opportunity for dementia prevention.”
To reach these conclusions, researchers examined health and genetic data from large groups of participants in Copenhagen and the U.K. Their analysis showed that higher body weight plays a direct role in increasing dementia risk.
How Genetics Helped Prove Cause and Effect
The research team was able to demonstrate causation by using a Mendelian randomization approach, a study design that closely mirrors the structure of a randomized controlled trial. In this method, common genetic variants that raise BMI act as stand-ins for BMI altering medications.
Just as participants in drug trials are randomly assigned to receive either a medication or a placebo, genetic variants linked to higher BMI are randomly passed from parents to children. This random assignment allows researchers to observe effects on disease outcomes without interference from lifestyle or environmental factors.
Because of this design, the scientists could clearly link high BMI to dementia risk without the usual confounding influences seen in observational studies.
Blood Pressure Plays a Major Role
The findings also showed that much of the increased dementia risk tied to obesity appears to be driven by high blood pressure. This suggests that preventing or treating both excess weight and hypertension could meaningfully lower the likelihood of developing dementia.
“This study shows that high body weight and high blood pressure are not just warning signs, but direct causes of dementia,” Frikke-Schmidt said. “That makes them highly actionable targets for prevention.”
What the Findings Mean for Prevention
Researchers noted that weight-loss medications have already been tested in people with early Alzheimer’s disease but did not slow cognitive decline once symptoms had begun. However, an important question remains unanswered.
“Weight-loss medication has recently been tested for halting cognitive decline in early phases of Alzheimer’s disease, but with no beneficial effect. An open question that remains to be tested is if weight-loss medication initiated before the appearance of cognitive symptoms may be protective against dementia. Our present data would suggest that early weight-loss interventions would prevent dementia, and especially vascular-related dementia,” she continued.
Reference: “High Body Mass Index as a Causal Risk Factor for Vascular-Related Dementia: A Mendelian Randomization Study” by Liv Tybjærg Nordestgaard, Jiao Luo, Frida Emanuelsson, Genevieve Leyden, Eleanor Sanderson, George Davey Smith, Mette Christoffersen, Shoaib Afzal, Marianne Benn, Børge G Nordestgaard, Anne Tybjærg-Hansen and Ruth Frikke-Schmidt, 22 January 2026, The Journal of Clinical Endocrinology & Metabolism.
DOI: 10.1210/clinem/dgaf662
Additional authors include Liv Tybjærg Nordestgaard of Copenhagen University Hospital – Rigshospitalet and the University of Bristol in Bristol, England; Jiao Luo, Frida Emanuelsson, and Mette Christoffersen of Copenhagen University Hospital – Rigshospitalet; Genevieve Leyden, Eleanor Sanderson, and George Davey Smith of the University of Bristol; Børge Nordestgaard and Shoaib Afzal of Copenhagen University Hospital – Herlev Gentofte and University of Copenhagen; and Marianne Benn and Anne Tybjærg-Hansen of Copenhagen University Hospital – Rigshospitalet and the University of Copenhagen.
The research was funded by the Independent Research Fund Denmark, the Capital Region of Denmark, the Lundbeck Foundation, Hjerteforeningen, and Sygeforsikringen Danmark.
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