Jan. 6, 2012
By Patricia Nicholson
Researchers have discovered another reason why belly fat may be bad for women’s health: it may have a role in the development of dementia and Alzheimer’s disease in women. A study from Tufts University in Boston links women’s dementia and Alzheimer’s risk to a hormone secreted by the type of fat that accumulates in the abdomen.
Earlier research established a link between cardiovascular risk factors (such as Type 2 diabetes, obesity and high blood pressure) with risk of cognitive decline. One possible explanation for the overlap between these cardiovascular risk factors and dementia risk factors is the inflammation and insulin resistance that are characteristics of Type 2 diabetes. The study authors wanted to look at the possible role of several factors that affect either inflammation or blood glucose, including a hormone called adiponectin. The researchers were interested in adiponectin not only because it plays a role in insulin signaling, but also because brain tissue contains receptors for adiponectin. This hormone is produced in abdominal fat.
The researchers followed 541 women and 399 men who were participating in the Framingham Heart Study and had no dementia at the start of the study. The participants’ levels of several substances that play a role in inflammation or in balancing blood glucose levels were measured between 1985 and 1988. They were then followed for 13 years, during which time a total of 159 people developed dementia, including 125 who had Alzheimer’s disease.
Adiponectin was the only one of the six substances measured in the participants’ blood that was significantly associated with a higher risk of dementia, and only in women. The other five substances tested (glucose, glycated albumin, insulin, high-sensitivity C-reactive protein and lipoprotein-associated phospholipase A2) did not appear to be linked to dementia or Alzheimer’s.
Women whose adiponectin levels were higher than the group’s median level were 63 per cent more likely to develop dementia and 87 per cent more likely to develop Alzheimer’s compared to women whose adiponectin levels were lower than the median.
The results are puzzling because adiponectin is known to increase sensitivity to insulin. Because people with Alzheimer’s disease have dysfunctional insulin signaling in their brains, adiponectin might be expected to have a protective effect against dementia. Future studies may help to show whether adiponectin itself increases dementia risk, or whether adiponectin levels may have been higher in the group that developed Alzheimer’s because levels increased in an attempt to protect the brain.