Alzheimer’s disease progression and body weight may be linked: Study

By Dr. Ananya Mandal, MDNov 22 2011

There have been studies that show that people who are overweight in middle age are more likely to develop Alzheimer's disease decades later than people at normal weight. However some studies also show that people in the earliest stages of Alzheimer's disease are more likely to have a lower body mass index (BMI).

A latest study published in the November 22, 2011, print issue of Neurology, the medical journal of the American Academy of Neurology, examined 506 people with advanced brain imaging techniques and analyses of cerebrospinal fluid to look for biomarkers for Alzheimer's disease, which can be present years before the first symptoms begin. The participants were part of the Alzheimer's Disease Neuroimaging Initiative, included people with no memory problems, people with mild cognitive impairment, or mild memory problems, and people with Alzheimer's disease.

The study finds that people with no memory or thinking problems and in people with mild cognitive impairment, those who had the Alzheimer's biomarkers were also more likely to have a lower BMI than those who did not have the biomarkers.

Results show that 85 percent of the people with mild cognitive impairment who had a BMI below 25 had signs of the beta-amyloid plaques in their brains that are a hallmark of the disease, compared to 48 percent of those with mild cognitive impairment who were overweight. The relationship was also found in people with no memory or thinking problems.

“These results suggest Alzheimer's disease brain changes are associated with systemic metabolic changes in the very earliest phases of the disease,” said study author Jeffrey M. Burns, of the University of Kansas School of Medicine in Kansas City and a member of the American Academy of Neurology. “This might be due to damage in the area of the brain called the hypothalamus that plays a role in regulating energy metabolism and food intake. Further studies should investigate whether this relationship reflects a systemic response to an unrecognized disease or a long-standing trait that predisposes a person to developing the disease.”

Burns said, “In general, we think of Alzheimer's as a brain disease, but this is evidence that there are systemic problems throughout the body in the early stages of Alzheimer's.”

Richard Lipton, an attending neurologist at Montefiore Medical Center, in New York City, who was not involved in the new research, agrees with the authors that the findings suggest that Alzheimer's can affect the entire body early on. “The most obvious manifestations of Alzheimer's disease are in the brain, but Alzheimer's disease has a large number of effects on the body as well,” said Lipton. “The brain regulates blood pressure and respiratory rate and pulse and hunger and satiety and blood flow to various organs in the body, so it wouldn't be surprising if a widespread disease of the brain had effects on many, many different aspects of bodily function,” he said.

May Ahmad Baydoun, a staff scientist at the National Institute on Aging who studies risk factors for dementia, described the study as “very strong” overall. But, she says, “the results would have been a lot stronger if they found weight loss over time is associated with increased Alzheimer's disease pathology, also over time.”

The relationship between weight loss and the progression of Alzheimer's is likely a two-way street, Lipton explained. People who start to experience declines in mental function may shop for groceries less regularly, cook less frequently, and eat less - and the poor nutrition that results could in turn accelerate the progression of the disease, he said. “It seems pretty likely to me that both things are true - that good health practices prevent illness, and health practices may fall apart in the early stages of illness and accelerate cognitive and physical decline,” Lipton said.

The study was supported by the University of Kansas Alzheimer Disease Center, the National Institute of Neurological Disorders and Stroke and the Eunice Kennedy Shriver National Institute of Child Health & Human Development.