Metabolic syndrome and risk of mortality in middle-aged versus elderly individuals: the Nord-Trøndelag Health Study (HUNT)

Recent reviews indicate that the metabolic syndrome is a risk factor for cardiovascular disease and mortality, but evidence is scarce in elderly individuals. We therefore examined the relationship between the metabolic syndrome and mortality rates among individuals aged 40–59, 60–74 and 75–89 years. We also examined whether the syndrome was associated with mortality rates over and above the Framingham risk score.

We studied prospectively 6,748 men and women who participated in the Nord-Trøndelag Health Study, Norway, from 1995 to 1997 (HUNT 2) and defined the metabolic syndrome by the International Diabetes Federation criteria.

During 53,617 person-years of follow-up (mean per person, 7.9 years), 955 individuals died, of whom 585 died from cardiovascular disease. Among individuals who were 40–59 years of age at baseline, the presence of the metabolic syndrome was associated with increased relative risk of cardiovascular and total mortality (age- and sex-adjusted hazard ratios 3.97 [95% CI: 2.00–7.88] and 2.06 [1.35–3.13], respectively, equivalent to population-attributable risks of 20.7 and 14.2%, respectively). The Framingham risk score accounted for less than one-third of the effect of metabolic syndrome on mortality rates. After the age of 60 years, the metabolic syndrome was not associated with increased mortality rates. We found a significant interaction between the metabolic syndrome and age on the relative risk of mortality. Results were confirmed in a sub-sample without cardiovascular disease at baseline.

The metabolic syndrome is a risk factor for mortality, over and above the Framingham risk score, in middle-aged, but not in elderly individuals.