Lifestyle
Larger belly in midlife means higher risk of dementia
By David Liu, Ph. D.
Mar 27, 2008 - 11:03:02 AM

THURSDAY March 27, 2008 (Foodconsumer.org) -- People with larger stomachs in their 40s have higher risk of dementia when they reach their 70s even if they are not overweight, obese or have no health conditions like diabetes, according to a study in the March 26, 2008 online issue of Neurology, the medical journal of the American Academy of Neurology.

The study showed people with a large belly who were overweight were 2.3 times more likely to have dementia than people with a normal weight and belly size.  For those who had both obesity and a large belly, the risk was 3.6 times higher compared to those of normal weight and belly size.   Those with a large belly even if they were not overweight or obese had still an 80 percent increased risk of dementia.

Researchers from Kaiser Permanente and other organizations who conducted the study cautioned that the study could not tell whether a large belly is a cause for dementia.  Other health-related factors may be responsible for the increased risk in the people with large bellies.  Abdominal obesity may or may not be part of the cause for dementia.  Further research needs to be completed to clarify this.

Earlier studies have linked central obesity determined by waist circumference and body mass index in the elderly and risk of dementia.  Large abdomens in midlife have been linked to other health problems in previous studies. But the current study linked midlife belly fat to the risk of dementia.

Abdominal obesity in midlife may better indicate the long term metabolic dysregulation that leads to dementia risk than abdomen size in older age, which tend to naturally lose muscle and bone mass and gain belly size, said Rachel Whitmer, PhD, lead author of the study at the Kaiser Permanente Division of Research in Oakland, CA.

"It is well known that being overweight in midlife and beyond increases risk factors for disease. However, where one carries the weight –especially in midlife -- appears to be an important predictor for dementia risk," she said.

"Autopsies have shown that changes in the brain associated with Alzheimer's disease may start in young to middle adulthood, and another study showed that high abdominal fat in elderly adults was tied to greater brain atrophy. These findings imply that the dangerous effects of abdominal obesity on the brain may start long before the signs of dementia appear." She explained.

But again more research is needed to confirm abdominal obesity in midlife is a contributing factor for dementia and if confirmed, then research needs to be completed to determine the underlying mechanisms for the link.

The study involved 6,583 people age 40 to 45 in northern California. The researchers measured participants' abdominal density which they said is highly correlated with visceral fat tissue wrapped around the organs. Belly fat was measured to determine the distance from the back to the upper abdomen, midway between the top of the pelvis and the bottom of the ribs, according to the researchers.

During the 36-year follow-up, 16 percent of the participants were diagnosed with dementia.  Abdominal obesity was more often found in non-whites, smokers, and people with high blood pressure, high cholesterol or diabetes and those with less than a high school level of education.

People with a large abdomen had an increased risk of dementia even if they had normal weight and were free of existing health conditions such as diabetes, stroke and cardiovascular disease, the study found.

Early studies associated later-life obesity with dementia. A study by Razay G and colleagues from the University of Tasmania in Launceston, Australia found people with abdominal obesity were 2.5 times more likely to have dementia. But people with obesity and overweight were 9.5 and 5.4 times, respectively, more likely to have the condition. The case-control study was published in the July 14, 2006 issue of Dementia and Geriatric Cognitive Disorders.

Previous studies also linked midlife body mass index to Alzheimer’s and dementia.  Whitmer and colleagues published a study in the April 2007 issue of Current Alzheimer Research showing that midlife body mass index is a strong indicator for both Alzheimer's and vascular dementia (VaD). They found compared to those with a normal BMI, people obese at midlife had 3.1 times increase in risk of AD and a 5 times increase in risk of VaD while those overweight in midlife were 2.1 times more likely to have AD and 2.0 times more likely to have VaD.  In terms of the mechanisms, whitmer said in another article in the same issue of the journal that adipocyte secreted proteins and hormones, and inflammatory cytokines could explain the link between adiposity or obesity and dementia.

Because BMI considers not only fat, but also lean muscle, it is generally believed that adiposity is linked with dementia risk and therefore abdominal obesity could be a better indicator of dementia risk.  Cereda E and colleagues from the University of Milan in Milan, Italy suggested in the Sept, 2007 issue of Age and Ageing that visceral adipose tissue rather than BMI should be considered as a factor in the development of dementia.  Among the theories proposed to explain the decline of cognitive functions, cardiovascular risk factors including dyslipidaemia, insulin resistance, blood pressure, adipocytokine/chemokines, atherosclerosis which have been associated with decline of cognitive functions seems strongly related to body fat distribution.

A health observer affiliated with foodconsumer.org said what consumers need to do to reduce risk of dementia is that they should not focus on the abdominal fat. Rather they should know why they get abdominal obesity, which is obviously affected by dietary habits among other things.  In fact, studies have showed dietary fat has been linked to cognitive decline.  Parrott MD and Greenwood CE from the University of Toronto reported in the Oct 2007 issue of Annals of the New York Academy of Sciences that diets high in fat, especially trans and saturated fats adversely affect cognition while diet high in fruits, vegetables, cereals and fish are linked to better cognitive function and lower risk of dementia although the mechanism behind the effect remained ill-understood.