Early-Stage Alzheimer's Linked to Lower BMI

Does your weight affect your odds of developing Alzheimer's? The answer seems to be "yes," although the crystal ball is still cloudy. Some studies show that people who are overweight in middle-age are more likely to develop Alzheimer's disease than people of normal weight, but a new study found an interesting twist: People in the earliest stages of Alzheimer's tend to have a lower mass body index (BMI).

A study reported in the medical journal Neurology examined 506 people using advanced brain imaging techniques and analyses of cerebrospinal fluid. They searched for biomarkers that can be present for years before the patient exhibits the earliest symptoms. The participants included people with normal memories, those who had mild cognitive impairment, and those with Alzheimer's disease.

The researchers found that those who had biomarkers for the disease — even though they currently had good memories or only mild cognitive impairment — were more likely to have a lower BMI than those who didn't have the biomarkers. In fact, 85 percent of those people with mild cognitive impairment and a BMI of below 25 had signs of the brain-wasting beta-amyloid plaques in their brains. In comparison, only 48 percent of those who were overweight and had mild cognitive impairment had signs of beta-amyloid plaques that are a hallmark of Alzheimer's. (A person with a BMI of less than 25 would weigh less than 175 pounds if they were 5-foot-10. A person 5-foot-4 would have to weigh less than 145.)

"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 Dr. Jeffrey M. Burns of the University of Kansas School of Medicine in Kansas City. "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," he said in a press release. "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."

The National Institute on Aging estimates that as many as 5.1 million Americans suffer from Alzheimer's. According to the Alzheimer's Association, it's the 6th leading cause of death in the United States and is the only cause of death among the top 10 in the United States without a way to prevent or cure.