Research Review by Dr. Shawn Thistle©

Date:

Nov. 2005

Study Title:

Obesity and the risk of myocardial infarction in 27000 participants from 52 countries: a case-control study

Authors:

Yusuf S et al.

Publication Information:

Lancet 2005; 366: 1640-1649.

Summary:

It is well known that obesity significantly raises one's risk of myocardial infarction (heart attack) and other heart-related diseases, as well as other afflictions such as diabetes and hypertension. Most of the data collected to date has involved subjects in high-income countries, despite the fact that the global burden for cardiovascular disease lies mostly in developing countries.

Further, simple clinical measurements to predict someone's risk of heart attack have not been firmly established.

Much attention has been given over the years to BMI (Body Mass Index) - which is calculated from height and body weight, and essentially represents someone's overall "density". This has become the standard measure used to assess a patient's cardiovascular risk. Waist and hip circumference and waist-to-hip ratio have also been used.

This study aimed to determine which of these simple clinical measurements best predicted future heart attack in a large group of patients (27000) from 52 countries.

Study participants were recruited in 262 centres in 52 countries in Asia, Europe, the middle east, Africa, Australia, and North and South America. Structured questionnaires and physical examinations were conducted in a consistent manner, obtaining information about demographic factors, socioeconomic status, lifestyle, risk factors, and personal and family history.

Pertinent Results:

  • Body Mass Index (BMI) showed only a modest and graded association with heart attack, which was substantially reduced when controlled for waist-to-hip ratio, and non-significant after controlling for other factors
  • Cases (those who suffered a heart attack) had a significantly higher waist-to-hip ratio (and hence, more abdominal fat) than controls - this was consistent in all regions of the world, in men and women, and in old and young individuals
  • Waist circumference was significantly associated with risk of heart attack in a graded fashion with no evidence of a threshold - this was continuous and persistent even after adjusting for BMI and height
  • A trend toward lower heart attack risk was noted with increasing hip circumference

Conclusions & Practical Application:

This large, diverse, case-control study indicates that waist-to-hip ratio is the strongest predictor of heart attack in men and women of all ages, ethnic origin, and independent of other risk factors (such as smoking, dyslipidemia, diabetes, hypertension). This study also demonstrated that the association of BMI with heart attack disappears when adjusted for other risk factors.

Common clinical practice involves calculating BMI to assess patient risk for future heart disease. Those of us in practice know that BMI is often elevated in muscular athletes and so we have been questioning its utility for the athletic population for years. This study provides evidence that waist-to-hip ratio, and even waist and hip circumference independently, are better predictors of future heart disease than BMI.

These results also support a multilevel approach to preventing heart disease, diabetes, and other obesity-related conditions. First, we need to emphasize abdominal fat loss in our patients. Second, some benefits may accrue from increasing hip circumference, which in most people would indicate an increase in muscle mass.

Overall, little is known about how to specifically reduce abdominal fat specifically, but what is known is that a balanced diet containing lots of fruits and vegetables, low fat protein sources, and whole grain sources of fibre, combined with a properly designed exercise program can help prevent many chronic disease and contribute to a healthy lifestyle.