The utility of metabolic syndrome (MetS) for predicting mortality among older adults, the highest-risk population, is not well established. In addition, few studies have compared the predictive utility of MetS to that of its individual risk factors.
We evaluated relationships of MetS (as defined by the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults [Adult Treatment Panel III (ATPIII)], International Diabetes Foundation [IDF], and World Health Organization [WHO]) and individual MetS criteria with mortality between 1989 and 2004 among 4258 US adults 65 years or older and free of prevalent cardiovascular disease (CVD) in the Cardiovascular Health Study, a multicenter, population-based, prospective cohort. Total, CVD, and non-CVD mortality were evaluated. Cox proportional hazards models were used to estimate the mortality hazard ratio (relative risk [RR]) predicted by MetS.
At baseline (mean age, 73 years), 31% of men and 38% of women had MetS (ATPIII). During 15 years of follow-up, 2116 deaths occurred. After multivariable adjustment, compared with persons without MetS, those with MetS had a 22% higher mortality (RR, 1.22; 95% confidence interval [CI], 1.11-1.34). Higher risk with MetS was confined to persons having elevated fasting glucose level (EFG) (defined as ≥ 110 mg/dL [≥ 6.1 mmol/L] or treated diabetes mellitus) (RR, 1.41; 95% CI, 1.27-1.57) or hypertension (RR, 1.26; 95% CI, 1.15-1.39) as one of the criteria; persons having MetS without EFG (RR, 0.97; 95% CI, 0.85-1.11) or MetS without hypertension (RR, 0.92; 95% CI, 0.71-1.19) did not have higher risk. Evaluating MetS criteria individually, we found that only hypertension and EFG predicted higher mortality; persons having both hypertension and EFG had 82% higher mortality (RR, 1.82; 95% CI, 1.58-109). Substantially higher proportions of deaths were attributable to EFG and hypertension (population attributable risk fraction [PAR%], 22.2%) than to MetS (PAR%, 6.3%). Results were similar when we used WHO or IDF criteria, when we evaluated different cut points of each individual criterion, and when we evaluated CVD mortality.
These findings suggest limited utility of MetS for predicting total or CVD mortality in older adults compared with assessment of fasting glucose and blood pressure alone.