A larger waistline, high blood pressure and other risk factors that make up metabolic syndrome are associated with an increased risk of early-onset dementia, according to a study published in Neurology®, the medical journal of the American Academy of Neurology. Early-onset dementia is diagnosed before the age of 65. The study does not prove that metabolic syndrome causes early-onset dementia, but merely demonstrates a link.
Numerous factors can influence the risk of dementia. Previous research by the University of Exeter and Maastricht University has already shown that a lower level of education, lower socio-economic status, genetic variations, lifestyle factors such as alcohol abuse and social isolation as well as health problems such as vitamin D deficiency, stroke, hearing impairment and heart disease significantly increase the risk of early-onset dementia. In addition to physical factors, mental health also plays an important role, including chronic stress, loneliness and depression.
Metabolic Syndrome and Dementia Risk
Metabolic syndrome is defined as excess abdominal fat plus two or more of the following risk factors: High blood pressure, high blood sugar levels, higher than average levels of triglycerides (a type of fat in the blood) and low levels of “good” cholesterol (HDL cholesterol). “While dementia is usually diagnosed at an older age, early-onset dementia occurs when a person is still working and may have a family,” said study author Dr. Minwoo Lee of Hallym University Sacred Heart Hospital in Anyang, South Korea. “Our study found that metabolic syndrome in middle age is a risk factor for early-onset dementia.”
For the study, the researchers analyzed national health insurance data in South Korea to identify nearly two million people between the ages of 40 and 60 who had undergone a health examination. The examination included measurements of waist circumference, blood pressure, blood glucose levels, triglyceride levels 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.
Among those with metabolic syndrome, the incidence rate was 0.86 cases per 1,000 person-years, compared with 0.49 cases among those without metabolic syndrome. Person-years represent both the number of people in the study and the time each person spent in the study. After adjusting for age, education level and health factors such as physical activity, depression and stroke, the researchers found that metabolic syndrome was associated with a 24% higher risk of dementia. When looking at specific forms of dementia, it was associated with a 12% increased risk of Alzheimer’s disease and a 21% increased risk of vascular dementia.
The researchers found that 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 forties had a higher risk than people in their fifties. The researchers found that 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.
A Healthy Lifestyle is Crucial
“Our results suggest that lifestyle changes to reduce the risk of metabolic syndrome, such as a healthy diet, regular exercise, maintaining a healthy weight, quitting smoking and reducing stress, may help reduce the risk of early-onset dementia,” said Lee. To confirm and extend their findings, further studies are needed that follow people over a longer period of time and look for biomarkers of dementia using brain scans. One limitation of the study was that the researchers did not look at genetic risk factors for Alzheimer’s disease.