Metabolic syndrome may protect the very old brain

By Will Boggs, MD

NEW YORK (Reuters Health) - The so-called metabolic syndrome is associated with slower cognitive decline among people older than 85 years, according to a new study.

Most research on the metabolic syndrome -- a cluster of risk factors such as high blood pressure, obesity and high blood sugar levels -- focuses on young adults or middle-aged populations, study investigator Esther van den Berg told Reuters Health.

"In these age-groups," she added, "the vascular risk factors that are part of the metabolic syndrome are clearly associated with atherosclerosis (hardening of the arteries), cardiovascular disease, and an increased risk of cognitive dysfunction and dementia. The results of our study show that these 'traditional' associations do not necessarily hold in a population of very old persons."

Ms. van den Berg from the University Medical Center Utrecht, The Netherlands and colleagues examined the relationship between the metabolic syndrome and cognitive decline in 497 people recruited at age 85 years to participate in the Leiden 85-Plus Study.

At the outset, there was no difference on any of the cognitive tests between study participants with and without the metabolic syndrome, the authors report.

Between age 85 and 90, however, the metabolic syndrome was associated with a slower decline on several standard tests of cognitive function.

Each additional metabolic syndrome risk factor present contributed to a decelerated decline in cognitive function, the investigators say, with elevated blood sugar level and body mass index showing the strongest associations.

"In very old persons the traditional vascular risk factors do not seem as detrimental as they are in middle-aged persons," Ms. van den Berg said. "The exact mechanisms that cause this are still largely unclear."

One possible explanation is that "we're looking at a population of survivors, who, despite having multiple risk factors, are somehow less susceptible to the adverse effects of hypertension (high blood pressure), obesity, and high cholesterol," Ms. van den Berg said.

"Our results might even suggest that at this high age, traditional risk factor such as hypertension and overweight are somehow protective against cognitive decline, for example by acting as some kind of 'reserve capacity,' but there is to date no clear evidence for this latter explanation," she concluded.

SOURCE: Neurology, September 4, 2007.