Metabolic syndrome and the risk of sudden cardiac death in middle-aged men

Abstract

Background

Little is known about the relationship between metabolic syndrome and sudden cardiac death (SCD). We examined the association of metabolic syndrome, as defined by World Health Organization (WHO), International Diabetes Federation (IDF), National Cholesterol Education Program (NCEP) and American Heart Association (AHA) — IDF interim criteria, with incident SCD. We also assessed the association of a continuous metabolic risk score with SCD.

Methods

A total of 1466 middle-aged men participating in a prospective population-based cohort study from eastern Finland with no history of coronary heart disease or diabetes at baseline were included.

Results

During the average follow-up of 21 years 85 SCDs occurred. Men with the metabolic syndrome as defined by the WHO, NCEP, IDF and interim criteria had a 2.2–2.6 fold, increased risk for SCD, after adjusting for lifestyle and traditional cardiovascular risk factors not included in the metabolic syndrome definition (P < 0.001–0.011). A one-standard deviation increase in the metabolic risk score (composed of the sum of Z-scores for waist circumference, insulin, glucose, high-density lipoprotein (HDL) cholesterol, triglycerides, and blood pressure) was associated with a 1.68-fold higher (95% CI 1.33-2.11) risk of SCD. Even when adjusting further for systolic blood pressure, HDL cholesterol and body mass index, the association remained significant for the interim criteria and the metabolic risk score, but not for WHO, NCEP, or IDF definitions.

Conclusions

Men with metabolic syndrome are at increased risk for SCD. Incident SCD associated with the IDF/AHA interim criteria and metabolic risk clustering estimated by a score is not explained by obesity or traditional cardiovascular risk factors.

Key messages

Men with metabolic syndrome are at increased risk for sudden cardiac death. Incident sudden cardiac death associated with metabolic risk clustering estimated by a score in not explained by obesity or traditional cardiovascular risk factors. Prevention of the metabolic syndrome may help reduce the health burden of SCD.

Introduction

Sudden cardiac death (SCD) accounts for one-half of all coronary heart disease (CHD)-related deaths. Since a majority of SCDs occur among the general segments of the population, the problem would require screening methods applicable to the general population. There continues to be interest in identifying clinically useful markers for SCD among the general population. Epidemiological studies have shown that half of the victims of SCD have no physician-diagnosed CHD at the time of death [1], [2].

Metabolic syndrome (MetS) is a common clinical condition with a prevalence varying from 10 to 40%, or even higher in older age groups, depending on the populations and definition of MetS [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]. A previous study found increased SCD risk for the metabolic syndrome based on the definitions of National Cholesterol Education Program III (NCEP-ATPIII) and International Diabetes Federation (IDF) with respect to SCD [3]. However, this previous study did not evaluate the risk of MetS for SCD based on World Health Organization (WHO) definition. Current definitions may also be criticized for the use of arbitrary dichotomous cut-offs for the features of the metabolic syndrome, even though risk factors such as blood pressure and high-density lipoprotein (HDL) cholesterol have continuous and dose-related associations with cardiovascular outcomes. Some researchers have therefore estimated metabolic risk as a continuous variable using the sum of the Z-scores of the individual metabolic risk factors [13], [14].

The objective of the present investigation was to evaluate SCD risk for the MetS as defined by the WHO, NCEP, IDF and IDF/American Heart Association (AHA) interim criteria and a metabolic risk score in a population-based cohort of middle-aged men who did not have coronary heart disease or diabetes at baseline.