Metabolic syndrome not a good predictor of death

NEW YORK (Reuters Health) - Among older adults, two components of the so-called "metabolic syndrome" - namely, high blood pressure and high blood sugar -- are better predictors of death from heart disease, or any cause, than all five components of the metabolic syndrome as a whole, research shows.

The five components of the metabolic syndrome are: obesity, high triglyceride levels, low "good" HDL cholesterol levels, high blood pressure (hypertension), and elevated fasting blood sugar levels.

The overall predictive value of the whole metabolic syndrome "has been questioned, and the ability of metabolic syndrome to identify mortality risk in older adults, the fastest growing segment of the population and the group at highest risk, is not clearly established," Dr. Dariush Mozaffarian, of Harvard School of Public Health, Boston, Massachusetts, and colleagues note in the latest issue of the Archives of Internal Medicine.

To clarify the situation, they assessed relationships of metabolic syndrome and individual metabolic syndrome components with death among 4,258 elderly adults participating in a heart health study.

At the outset, 31 percent of men and 38 percent of women had metabolic syndrome. A total of 2,116 deaths occurred during 15 years of follow-up.

Results showed that those with metabolic syndrome had a 22 percent higher risk of dying compared to those without metabolic syndrome. But the higher mortality risk associated with metabolic syndrome was confined to individuals who had elevated fasting blood sugar levels or hypertension as one of the criteria, according to the team.

Patients with metabolic syndrome but no elevated blood sugar or hypertension did not have a higher risk.

When the investigators assessed metabolic syndrome criteria individually, they found that only elevated fasting blood sugar and hypertension predicted higher mortality. Mortality was 82 percent higher among subjects with both elevated fasting blood sugar and hypertension compared to those with neither condition.

The total proportion of deaths attributable to hypertension and elevated blood sugar was 22.2 percent, which is substantially higher than the proportion attributable to metabolic syndrome (6.3 percent).

These findings, Mozaffarian and colleagues conclude, suggest "limited utility" of the metabolic syndrome concept for predicting death in older men and women compared with assessment of fasting blood sugar level and blood pressure alone.

SOURCE: Archives of Internal Medicine, May 12, 2008.