A new study has found that people with certain health problems in their 40s and 50s—such as high blood pressure, excess belly fat, and high blood sugar—may have a greater chance of developing dementia before the age of 65.
This condition is known as young-onset dementia, and although it is less common than dementia in older people, it can be especially difficult because it affects people during their working years or while raising families.
The study was published online on April 23, 2025, in Neurology, the journal of the American Academy of Neurology. It looked at a group of nearly two million people in South Korea aged 40 to 60 who had health check-ups through the national health insurance system.
These check-ups included measurements of waist size, blood pressure, blood sugar, cholesterol, and triglyceride levels (a type of fat in the blood).
The researchers were studying metabolic syndrome, a cluster of risk factors that together increase the risk of heart disease, stroke, and type 2 diabetes.
A person is considered to have metabolic syndrome if they have extra fat around their waist along with at least two of the following: high blood pressure, high blood sugar, high triglycerides, and low levels of HDL (“good”) cholesterol.
In this study, about 25% of the participants had metabolic syndrome. The researchers followed the participants for an average of eight years. During that time, about 8,900 people (0.45% of all participants) developed dementia.
The rate of dementia was higher among people with metabolic syndrome: 0.86 cases per 1,000 person-years, compared to 0.49 cases among those without it. “Person-years” is a way to measure both the number of people in a study and how long each person was followed.
After taking into account other possible factors like age, physical activity, depression, education level, and history of stroke, the researchers found that people with metabolic syndrome had a 24% higher risk of developing young-onset dementia.
When they looked at different types of dementia, they found a 12% increased risk of Alzheimer’s disease and a 21% increased risk of vascular dementia, which is caused by problems with blood flow in the brain.
The risk also varied by sex and age. Women with metabolic syndrome had a 34% higher risk of dementia, while men had a 15% higher risk. The effect was stronger in people in their 40s compared to those in their 50s.
Even having just one part of metabolic syndrome increased dementia risk, but the more problems a person had, the higher the risk became. People with all five parts of metabolic syndrome had a 70% higher chance of developing dementia.
Dr. Minwoo Lee, the lead author of the study and a physician at Hallym University Sacred Heart Hospital in South Korea, said the findings show the importance of taking care of your health in midlife.
He recommends lifestyle changes like eating well, staying active, keeping a healthy weight, quitting smoking, and managing stress to lower the risk of metabolic syndrome and possibly also dementia.
The study does not prove that metabolic syndrome directly causes dementia, but it shows a strong link between the two. One limitation of the research is that it didn’t consider genetic factors that could influence a person’s risk of Alzheimer’s disease.
Also, the study didn’t use brain scans to look at changes in the brain over time, which could give more information about how metabolic syndrome affects brain health.
Still, this study adds to growing evidence that what happens in your 40s and 50s can have a big impact on your brain health later. It shows that conditions we often think of as physical health problems—like high blood pressure or blood sugar—can also affect the brain, even leading to early memory loss and other signs of dementia.
More research is needed to understand why and how this happens, but the message is already clear: taking care of your heart and metabolism might also protect your brain.
If you care about dementia, please read studies about low choline intake linked to higher dementia risk, and how eating nuts can affect your cognitive ability.
For more information about brain health, please see recent studies that blueberry supplements may prevent cognitive decline, and results showing higher magnesium intake could help benefit brain health.
The research findings can be found in Neurology.
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