Metabolic syndrome linked to increased risk of young-onset dementia

Metabolic syndrome is defined as having excess belly fat plus two or more of the following risk factors: high blood pressure, high blood sugar, higher than normal triglycerides, which are a type of fat found in the blood, and low high-density lipoprotein (HDL) cholesterol, or "good" cholesterol.

"While most dementia is diagnosed in older age, young-onset dementia occurs while a person is still working and perhaps raising a family," said study author Minwoo Lee, MD, PhD, of Hallym University Sacred Heart Hospital in Anyang, South Korea. "Our study found having metabolic syndrome in middle age is a risk factor for young-onset dementia."

For the study, researchers reviewed national health insurance data in South Korea to identify nearly two million people between the ages of 40 and 60 who had a health check-up. The check-up included measurements of waist circumference, blood pressure, blood sugar, triglyceride and cholesterol levels. Of all participants, 25% had metabolic syndrome.

Over an average follow-up period of eight years, 8,921 people, or 0.45% of all participants, developed dementia. For those with metabolic syndrome, the incidence rate was 0.86 cases per 1,000 person-years, compared to 0.49 cases for those without metabolic syndrome. Person-years represent both the number of people in the study and the amount of time each person spends in the study.

After adjusting for age, education and health factors such as level of physical activity, depression and stroke, researchers found metabolic syndrome was associated with a 24% higher risk of dementia. When looking at specific types of dementia, it was associated with a 12% increased risk of Alzheimer's disease and a 21% increased risk of vascular dementia.

Researchers found female participants with metabolic syndrome had a 34% increased risk of dementia compared to male participants who had a 15% increased risk. People in their 40s had a greater risk than people in their 50s.

Researchers found each component of metabolic syndrome was associated with an increased risk of dementia, which was cumulative. People with all five components had a 70% increased risk of dementia.

"Our findings suggest that lifestyle changes to reduce the risk of metabolic syndrome, such as eating a healthy diet, exercising regularly, maintaining a healthy weight, quitting smoking and reducing stress, may help reduce the risk of young-onset dementia," said Lee. "Future research that follows people over longer periods of time and uses brain scans to look for biomarkers of dementia is needed to confirm and expand upon our findings."

A limitation of the study was that researchers did not review genetic risk factors for Alzheimer's disease.

The study was supported by the Korean National Research Foundation.