What is a risk factor for dementia? A new study shows an association between a large waist size and the development of cognitive impairment. This study provides more evidence that lifestyle matters when it comes to dementia.

Waist circumference is a more accurate indicator of abdominal visceral fat level than body mass index (BMI) in the elderly, according to a report published in Obesity, the flagship journal of The Obesity Society.

Waist Size is Risk Factor for Dementia

The study is the first large-scale cohort to examine the association of late-life waist circumference with the incidence of dementia in an older population.

According to study author Hye Jin Yoo, associate professor at Korea University Guro Hospital, “For all the physicians who deal with geriatric medicine, obesity and dementia, this study emphasizes that waist circumference should be considered in the assessment of obesity-related dementia risk in the elderly.”

How the Study Determined that Waist Size is a Risk Factor for Dementia

A 2015 large-scale retrospective cohort study of nearly 2 million people from the United Kingdom Clinical Practice Research Datalink showed that the incidence of dementia continued to fall for every increasing BMI category.

The study, titled “Association Between Waist Circumference and Dementia in Older Persons: A Nationwide Population-Based Study” will be published in the November 2019 print issue.

• To help determine a healthy waist circumference, researchers compared relative risk of dementia associated with waist circumference and BMI categories using the Korea National Health Insurance Service program.

• The program is a mandatory social health insurance program that enrolls about 98 percent of Koreans who participate in biannual standardized health examinations.

• The study population comprised 872,082 participants aged 65 years and older who participated in the Korean national health screening examination between January 1, 2009 and December 31, 2009.

• The study population was observed from baseline until the date of development of dementia, death, or until December 31, 2015, whichever came first.

• Interviews with study participants included questions such as age, smoking status, alcohol consumption and exercise level.

• The study used health insurance premiums as a substitute variable for income level. A history of diabetes, hypertension and cardiovascular disease diagnosed by a physician was also identified.

• The health examination included the calculation of BMI as measured weight in kilograms divided by measured height in meters squared.

• Waist circumference was measured at the narrowest point between the lower border of the rib cage and the iliac crest during minimal respiration.

The study took into account the participants’ other health risks.

Dementia Risk Factor Study Results

The results of the study showed as follows:

Participants with a waist circumference of greater than or equal to 35 inches (90 cm) for men and 33.5 inches (85 cm) for women had a significantly increased risk of dementia.

• This risk existed after adjusting for other factors such as age, BMI, blood pressure, cholesterol, liver function tests and various lifestyle factors.

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