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Big Belly May Expand Risk of Dementia

By Mary Pickett, M.D.
Content provided by the Faculty of the Harvard Medical School

Having a big belly in middle age could increase your risk of dementia in old age, a study suggests. More than 6,500 men and women in their 40s were measured front to back using calipers. A distance of more than 10 inches was considered high. About 35 years later, nearly 1 in 6 people had developed Alzheimer's disease or another form of dementia. People who had big bellies in their 40s were nearly twice as likely to have dementia. This was true even for people who had normal body weight but extra fat in the belly. Overweight people were even more likely to have dementia if their weight was concentrated in the belly. The Associated Press wrote about the study March 27. It was in the journal Neurology.

What Is the Doctor's Reaction?

Are you an apple or a pear? New research shows that "apple shaped" adults who had an oversized waist at age 40 to 45 are now having dementia at greatly increased rates.

This is stunning news. Until now, we have had few ways to predict and prevent dementia. The study didn't prove that obesity was a direct cause of dementia. However, the association was so great that experts say reversing obesity is likely to reverse risks.

Waist size in the study was recorded as a straight line from back to front. An instrument called a caliper was used. A distance above 25 centimeters was considered oversized. Of the 6,583 people studied, 16% developed dementia.

People with larger waists had about double the dementia risk of people with normal or small waists. This was true even if their body mass index (BMI) was normal. People who were obese (BMI over 30) and also had a larger waist had 3 1/2 times the dementia risk of a person with normal waist size and BMI.

We have had good reasons to pay attention to body shape and waist size before now. Abdominal obesity increases the risk of heart disease, diabetes, high blood pressure, liver inflammation and scarring, and unhealthy cholesterol levels. Studies have also shown that a high BMI can lead to stroke, sleep apnea, some kinds of cancer, osteoarthritis, gallstones and early death.

Americans fear dementia more than any of these other health issues. A link between waist size and dementia should be a powerful motivator for us to slim down. More than half of American adults have abdominal obesity.

What Changes Can I Make Now?

A mind is a terrible thing to "waist." Let's find out whether you are at risk from obesity.

Which is the best measure for obesity, waist size or body mass index (BMI)? Truly, you should measure both. You have health risks if either one is oversized.

The standard way to measure your waistline is by using a soft (paper or cloth) tape measure. Get help from a partner, for accurate measurement. Stand up. Place the tape right above the top of your pelvic bones, which are at each side of your waist. Make sure the tape measure is not slanted as it goes around you. Compare your measurement to the standards listed below.

BMI is determined by an equation using weight and height. You can use a BMI calculator.

For whites, Hispanics and blacks:

  • A waist larger than 40 inches is abnormal for men. About 35 inches is abnormal for women.

  • You have normal weight if your BMI is 18.5 to 24.9 and your waist size is normal.

  • You are considered overweight if your BMI is 25 to 29.9 or your waist is larger than normal.

  • A BMI that is 30 or higher is considered obese, regardless of your waist size.

Asians have a larger percentage of body fat. They have risks from more modest weight gain. For Asians:

  • A waist size of 35.4 inches or more is abnormal for men. About 31.5 inches or more is abnormal for women.

  • You have normal weight if your BMI is 18.5 to 22.9 and your waist size is normal.

  • You are considered overweight if your BMI is 23 to 29.9 or your waist is larger than normal.

  • A BMI that is 30 or higher is considered obese, regardless of your waist size.

As old fashioned as it sounds, modest calorie intake and regular exercise are still the cornerstones of weight management.

For most people, the best way to lose weight is to make a gradual but permanent change in calorie intake and to increase exercise. Reducing portion size and choosing lower calorie foods are good strategies.

Prescription weight loss drugs have limited use because of expense and side effects.

People with severe obesity can speed weight loss with surgery. For the right person, obesity surgery can be a successful treatment and can improve health. Surgery is not an easy way out of obesity.

If you are overweight and have extra risk factors for diabetes, try to lose at least 5% of body weight and keep it off. This can lower your risk for diabetes by about half, at least for the next several years.

What Can I Expect Looking to the Future?

Up to now, most people have considered obesity to be a personal burden, not a burden to society. Dementia may change this perception. This condition requires caregiving and community resources. If society has an interest in reducing obesity, we will need to contribute societal support.

It is hard for people to change habits and manage weight if their community does not offer incentives. We have seen this phenomenon with smoking. Some people have the interest and willpower to quit on their own. But quit rates have increased since smoking bans and cigarette taxes have been more widely used. I suspect we will need similar motivators (such as insurance incentives) for dieting and exercise. Then perhaps we can get our arms around this weighty problem.

Last Annual Review Date: 2008-03-28T00:00:00-06:00

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