Metabolic syndrome associated with cognitive decline in elderly persons

Elderly individuals with the metabolic syndrome, a grouping of several common conditions including abdominal obesity, low level of high-density lipoprotein (HDL, the “good cholesterol”), hypertension, and high triglyceride and blood sugar levels, are more likely to experience cognitive impairment than those without this syndrome, according to a study in the November 10 issue of JAMA.

The researchers also found a link with high measurements of certain proteins in the blood and the metabolic syndrome and impairment.

According to background information in the article, several studies have reported an association between the metabolic syndrome and cardiovascular disease. Despite an increasing awareness that cardiovascular risk factors increase risk of cognitive decline and dementia, there is little data on any link between the metabolic syndrome and cognition.

Kristine Yaffe, M.D., from the University of California, San Francisco, and colleagues investigated the association between the metabolic syndrome and high inflammation with change in cognition. Inflammation was defined as elevated levels of the proteins interleukin 6 and C-reactive protein in the blood. Participants, aged 70 to 79 years, were part of the Health, Aging and Body Composition (ABC) study, conducted from 1997 to 2002. Average age of the 2,632 participants at the study’s onset was 74 years; 52 percent were women; 40 percent were black. Participants were reevaluated at three and five years.

The researchers found that compared with those without the metabolic syndrome (n = 1,616), persons with the metabolic syndrome (n = 1016) were 20 percent more likely to develop cognitive impairment (defined as at least a 5 point decline on the Modified Mini-Mental State Examination [3MS], a standard cognitive test). Those with both metabolic syndrome and high inflammation (n = 348) were 66 percent more likely to have cognitive impairment than those without the metabolic syndrome. The 668 participants who had the metabolic syndrome and low inflammation did not show an increased likelihood of impairment. Also, those with the metabolic syndrome and high inflammation had greater four-year decline in cognitive testing scores than those without the metabolic syndrome, while those with the metabolic syndrome and low inflammation did not.

“To our knowledge, this is the first study to document that the metabolic syndrome is associated with poor cognitive outcomes,” the researchers write. “Future studies will need to address whether preventing the metabolic syndrome or lowering inflammation prevents cognitive impairment in elderly individuals.”