The Cardiometabolic Syndrome and Risk of Mortality From Cardiovascular Diseases and All Causes Among African Americans and White Americans

Introduction

The prevalence of diabetes mellitus (DM) is increasing in the United States with serious health and economic consequences. Data from the 2011 National Diabetes Fact Sheet indicates that about 18.8 million people are diagnosed with DM, and an additional 7.0 million are afflicted but undiagnosed. The national cost of DM in 2007 exceeded $174 billion in the United States. This estimate included $116 billion in excess medical expenditures attributed to DM, as well as $58 billion in reduced national productivity. People diagnosed with DM, on average, have medical expenditures that are approximately 2.3 times higher than the absence of DM diagnosis.(1) Risk factors for DM have been extensively studied. For over a century, investigators have observed that insulin resistance, hypertension, dyslipidemia, and obesity are predictors of the development of DM. Further studies have demonstrated that having this group of cofactors increases the risk of cardiovascular disease, more so even than the risk effect caused by elevated low-density lipoprotein cholesterol alone. Today, this group of cofactors is known as the “metabolic syndrome” or “cardiometabolic syndrome (CMS),” originally identified in 1988 as “syndrome X” by Gerald M. Reaven.(2–6) Prevalence of CMS is increasing rapidly worldwide and has become a major public health problem. In the United States, an estimated 50 million or more Americans have the syndrome.(7) Although several studies have examined prevalence of CMS and its associations with cardiovascular disease (CVD) and all cause mortality,(6–9) the magnitude of individual CMS components and CMS on CVD and all cause mortality by race/ethnicity remains to be established, and evidence from nationally representative data using a prospective analysis approach is scarce. To fill this gap, we used a large-scale dataset (n=9791) from the Third National Health and Nutrition Examination Survey (NHANES III) Linked Mortality File (1988–2006) to examine these associations for African American (AA) and White participants in the NHANES III.(10) We hypothesized that there were significantly different distributions of individual components of CMS by race/ethnicity, and that CMS significantly predicted risk of mortality among African Americans and Whites. We further tested the hypothesis that the CMS-mortality associations were mediated by serum inflammatory factors as previous studies have reported findings of subjects with CMS having increased serum C-reactive protein (CRP) and fibrinogen concentrations (two major biomarkers of inflammation).(11, 12)

Abstract

AIM

Studies using representative national data to prospectively examine associations between cardiometabolic syndrome (CMS) and mortality risk from cardiovascular diseases (CVD) and all causes by race/ethnicity are scarce. We tested the association using the Third National Health and Nutrition Examination Survey Linked Mortality File (1988–2006).

METHODS

CMS is defined using criteria from the National Cholesterol Education Program, with minor modifications based on criteria from the American Heart Association. Associations between CMS and mortality risk in those aged ≥35 years old were examined prospectively using Cox proportional hazard regression models.

RESULTS

The results indicate that almost one third of Americans aged ≥35 years have CMS. There were significant differences in prevalence of CMS components between African American and White participants. Multivariable-adjusted hazard ratios (95% CI) of CMS for CVD and all cause mortality were 1.34 (1.10–1.64), and 1.36 (1.21–1.54) in African Americans, and 1.31 (1.17–1.46) and 1.22 (1.13–1.31) in Whites. The CMS-mortality associations were greatly reduced after adjustment for inflammatory biomarkers.

CONCLUSIONS

CMS significantly predicts CVD and all cause mortality. The high prevalence of CMS poses a serious health problem in the United States. Specific attention should be paid to the significant race/ethnicity differences in CMS components rates and the effects of inflammatory disorders on CMS-mortality association when designing programs for prevention and treatment of the syndrome.

Keywords

cardiometabolic syndrome, CVD, all cause mortality