Risk Factors for Heart Failure

Summarized by Robert W. Griffith, MD
September 12, 2005

Introduction

The main causes of congestive heart failure (CHF) are high blood pressure and coronary heart disease. However, obesity and diabetes are important additional causes. Scientists in Uppsala, Sweden, decided to see if there is a common factor in obesity and diabetes that might account for the CHF risk; insulin resistance is found in both conditions, and might be the culprit. The results of their study have been reported in the Journal of the American Medical Association, and are summarized here.

What was done

The study employed volunteers taking part in the Uppsala Longitudinal Study of Adult Men. A group of 1187 men aged 70 and older, who were free of heart disease at baseline, were enrolled between 1990 and 1995. They were followed until 2002, i.e. for 7 to 12 years.

Insulin resistance was measured using a blood test known as the 'euglycemic insulin clamp glucose disposal rate', which was done at baseline. In addition, information was gathered on weight, height, blood pressure, glucose tolerance, and lipid levels.

There were 104 definitive cases of CHF diagnosed during the follow-up stage, after validation of all questionable cases; 87 were in subjects without diabetes, and 80 in patients without obesity (BMI over 30).

The risk of developing CHF was analyzed statistically for 5 sets of models: unadjusted, adjusted for diabetes at baseline, adjusted for diabetes plus other risk factors for CHF present at baseline, the same plus a heart attack during follow-up, and the same, plus results of insulin resistance testing. For the last set, the participants were distributed into 4 groups according to their degree of insulin resistance.

What the analyses showed

By comparing the results from the different sets of adjustments it was possible to determine the most significant risk factors for the development of CHF.

The presence of diabetes (based on a raised 2-hour blood glucose level after a standard glucose drink, or the serum proinsulin level) was a significant predictive factor for CHF. A raised body mass index (BMI) and an increased waist circumference were also predictors. On the other hand, a decrease in insulin resistance was linked to a decreased risk of CHF.

Further analyses showed that, if the results were adjusted to allow for differences in insulin resistance, the role of overweight and waist size was no longer significant. In other words, insulin resistance may be the principal change leading to CHF in non- diabetics and those without other known risk factors like smoking, high blood pressure, etc.

What this means

The analyses used in this study are complex, but they show clearly that insulin resistance predicts the development of CHF independently of other established risk factors, including diabetes. From a practical point of view, it means that if you are obese but have no evidence of increased insulin resistance you are not at increased risk of getting CHF (unless you smoke, of course, or have high blood pressure, etc.) So, it's possible to be overweight and healthy - just keep your eye on your blood sugar, blood pressure, your diet, your physical activity, and don't smoke!

Source

• Insulin resistance and risk of congestive heart failure. E. Ingellsson, J. Sundstrom, J. Arnlov,  et al., JAMA, 2005, vol. 294, pp. 334--341

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