Abdominal Obesity as a Risk Factor for CVD

Obesity is increasingly recognized as an important risk factor for cardiovascular disease (CVD). As a common measure of obesity, body mass index (BMI) predicts CVD risk. However, not every individual with an elevated BMI carries excess visceral adipose tissue, which appears to be the most important source of risk factors, such as insulin resistance, elevated triglycerides, low high-density lipoprotein (HDL) levels, and hypertension. At any given BMI, greater levels of accumulated visceral fat are associated with a worse cardiometabolic risk profile and increased mortality risk.

Researchers have proposed the hypertriglyceridemic waist phenotype as a potential risk assessment tool that accounts for abdominal obesity and its associated metabolic changes. For men, the hypertriglyceridemic waist phenotype is defined as a waist circumference of 90 cm (35.4 inches) or more and a triglyceride level of 2.0 mmol/l (177 mg/dL) or more. For women, the criteria for the hypertriglyceridemic waist phenotype are a waist circumference of at least 85 cm (33.5 inches) and a triglyceride level of at least 1.5 mmol/l (133 mg/dL).

In the current study, Prof. Arsenault and colleagues examined the association between the hypertriglyceridemic waist phenotype and CAD risk and whether the phenotype could improve risk prediction beyond traditional CVD risk factors. The EPIC-Norfolk cohort analysis included 21,787 men and women aged 45 to 79 years who were followed for a mean of 9.8 years [Arsenault BJ et al. CMAJ 2010].

The Hypertriglyceridemic Waist Phenotype and CAD Risk

Patients with the hypertriglyceridemic waist phenotype had an altered cardiometabolic risk profile compared with men and women with normal waist and/or triglyceride measures. In particular, the hypertriglyceridemic waist phenotype was associated with:

• Higher systolic blood pressure levels (p<0.001)

• Higher apolipoprotein B levels (p<0.001)

• Higher C-reactive protein levels (p<0.001)

• Lower HDL levels (p<0.001)

• Lower apolipoprotein A-I levels (p<0.001)

• Smaller low-density lipoprotein particles (p<0.001)

Increased waist circumference and elevated triglyceride levels significantly predicted risk of CAD. Men with the hypertriglyceridemic waist phenotype were more than twice as likely to develop CAD as men who did not have the phenotype (HR, 2.40; 95% CI, 2.02 to 2.87). The risk for CAD increased more than 3-fold for women with the hypertriglyceridemic waist phenotype compared with women who did not have the phenotype (HR, 3.84; 95% CI, 3.20 to 4.62).

Compared with normal values, the presence of either an increased waist circumference or hypertriglyceridemia reduced the probability of survival without CAD among both men and women. However, the presence of both an increased waist circumference and an elevated triglyceride level was associated with the worst disease-free survival (p<0.001) for both men and women.

By providing additional information about excess abdominal adiposity and associated metabolic abnormalities, the hypertriglyceridemic waist phenotype could have the potential to improve traditional CVD risk assessment tools. In the current analysis, Prof. Arsenault and colleagues evaluated the risk of coronary heart disease (CHD) according to Framingham risk scores and the hypertriglyceridemic waist phenotype. Even among men and women with the lowest Framingham risk score (≤10%), those with the hypertriglyceridemic waist phenotype were at greater risk of CHD than those without the phenotype.

Even though the hypertriglyceridemic waist phenotype is a robust marker of abdominal obesity, it can not be used on its own to fully assess a patient's risk of CAD, Prof. Arsenault said. Instead, the phenotype should be used together with existing CVD risk prediction algorithms, such as the Framingham risk score, to provide a better assessment of global cardiometabolic risk.