Researchers have found a possible connection between a hormone found in body fat and the risk of dementia, adding to the growing evidence on the potential link between the condition and diabetes.

A new study found that women with high levels of a hormone called adiponectin were at an increased risk of developing dementia. Scientists say the findings reflect the complicated and still unclear relationships between metabolism, hormones and the brain degeneration that occurs in dementia.

The researchers studied frozen blood samples from 840 of the participants from the large Framingham Heart Study, taken after the patients had been monitored for 13 years. In the 159 people who developed dementia, researchers found high levels of adiponectin.

Adiponectin helps the body use insulin to deliver fuels like glucose to different cells, such as the neurons in the brain. Study author Dr. Ernst Schaefer, a professor of medicine and nutrition at Tufts University, said he and his colleagues were surprised to find that women with high levels of the hormone had an increased risk of dementia.

"Adiponectin is supposed to be beneficial. It's supposed to decrease your risk of diabetes, supposed to decrease the risk of heart disease. But in this particular study, to our surprise, it increased the risk of dementia," Schaefer said.

The researchers also found high levels of the hormone in the men with dementia, but Schaefer said there were not enough men in the study to establish a link as strong as the one in women.

Previous studies have connected diabetes and dementia, suggesting that the condition's characteristic cognitive decline may be the result of malfunctions in the way the brain's cells respond to insulin.

Other research has also suggested that obesity, which often goes hand-in-hand with type 2 diabetes, may be another risk factor for dementia. However, most of the people in the current study were not obese and, with an average age of 88, were older than the patients studied in most dementia research.

"Different people have different metabolic set points and that can change over the lifespan," said Dr. Samuel Gandy, professor of Alzheimer's disease research at Mount Sinai School of Medicine. "In one group, you have midlife obesity leading to late-life complications; in another group, there might be not obesity but instead late life weight loss, and that can also lead to complications."

Scientists say far more research is needed before they can truly understand the connection between metabolism and dementia or know precisely what that connection means for the prevention and treatment of dementia.

"This study just reinforces our need for much more research on the relationship of insulin signaling to brain function and then its relationship to dementing illnesses such as Alzheimer's disease," said Dr. Roger Brumback, a neurologist at the Creighton University School of Medicine in Omaha.