Excess abdominal fat in middle age linked to increased risk of dementia later in life
by Craig Weatherby
Caution… gaining an extra inch (or foot) around your belly may end up costing you more than a new set of clothes.
A study by scientists at the Kaiser Permanente Division of Research shows that people in their 40s with larger stomachs—so-called “central obesity”—have a higher risk of developing dementia.
Evidence from prior studies indicates that being obese or overweight raises the risk of all forms of dementia, including Alzheimer's disease (AD), and that being obese or overweight also promotes the degenerations in brain function associated with dementia.
Research has also shown that having a large abdomen in midlife increases the risk of diabetes, stroke, and heart disease.
There's plenty of evidence that excess belly fat is a bigger risk factor for cardiovascular disease and diabetes than being obese.
But until now, no researchers had investigated whether the same pattern holds true for risk of dementia.
The findings of the new Kaiser Permanente show a similar link between belly fat and dementia, and suggest that the degenerative changes underlying dementia begin decades earlier.
As lead author Rachel Whitmer, Ph.D. wrote in an evidence review published last year, “There is a need to take a ‘life course approach’ and to consider the role of risk factors prior to the onset of old age” (Whitmer RA, April 2007).
Dr. Whitmer made these key observations (KP 2008):
- “Capturing abdominal obesity in midlife may be a much better indicator of… dementia risk. Measuring abdomen size in older age people may not be as good an indicator because as people age they tend to naturally lose muscle and bone mass and gain belly size.”
- “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."
And being underweight late in life is also associated with dementia, so by the time you reach your late sixties it may be a bad idea to lose lots of weight in an attempt to forestall mental fog.
What the study showed
Dr. Whitmer’s Kaiser Permanente team analyzed the medical records of 6,583 people in Northern California who had had their "abdominal density" measured between 1964 and 1973, when they were 40 to 45 years old (Whitmer RA et al. 2008).
The Kaiser Permanente team then looked for diagnoses of dementia in the subjects’ medical records an average of 36 years later (from January 1, 1994, to June 16, 2006).
As it turned out, some 16 percent of the participants were diagnosed with dementia years after their belly fat was measured.
The people who had a large belly and were overweight were 2.3 times (230 percent) more likely to develop dementia than people with a normal weight and belly size.
People who had a large belly and were obese were 3.6 times (360 percent) more likely to develop dementia than those of normal weight and belly size.
Those who were overweight or obese but did not have a large abdomen were still at increased risk, but they were only 80 percent more likely to have developed dementia.
Having a big belly raised the risk of dementia regardless of whether the participants were of normal weight, overweight, or obese, and regardless of existing health conditions, including diabetes, stroke and cardiovascular disease.
(The people more likely to have abdominal obesity included non-whites, smokers, people with high blood pressure, high cholesterol or diabetes, and those with less than a high school level of education.)
As the authors wrote, “Fifty percent of adults have central obesity; therefore, mechanisms linking central obesity to dementia need to be unveiled.”
As with all such studies, it is possible that the statistical association between big bellies and dementia stems from a complex set of health-related behaviors that raise the risk of dementia and abdominal obesity simultaneously.
But that seems unlikely, given the known connections between abdominal obesity and cardiovascular disease and the connections between cardiovascular disease and dementia.
- Kaiser Permanente (KP). Kaiser Permanente Study Shows That a Larger Abdomen in Midlife Increases Risk of Dementia. March 26, 2008. Accessed online March 30, 2008 at http://xnet.kp.org/newscenter/pressreleases/nat/nat_080326_abdomen.html
- Whitmer RA, Gunderson EP, Quesenberry CP Jr, Zhou J, Yaffe K. Body mass index in midlife and risk of Alzheimer disease and vascular dementia. Curr Alzheimer Res. 2007 Apr;4(2):103-9.
- Whitmer RA, Gustafson DR, Barrett-Connor E, Haan MN, Gunderson EP, Yaffe K. Central obesity and increased risk of dementia more than three decades later. Neurology. 2008 Mar 26; [Epub ahead of print]
- Whitmer RA. The epidemiology of adiposity and dementia. Curr Alzheimer Res. 2007 Apr;4(2):117-22. Review.
- Whitmer RA. Type 2 diabetes and risk of cognitive impairment and dementia. Curr Neurol Neurosci Rep. 2007 Sep;7(5):373-80. Review.