Obesity is a killer in its own right, irrespective of other biological or social risk factors traditionally associated with coronary heart disease, according to a study published online Feb. 14 in Heart.
Increasing weight is associated with a higher prevalence of known risk factors for coronary artery disease, such as diabetes, high blood pressure and cholesterol. And it has been assumed that these have been responsible for the increased risk of heart disease seen in obesity, according to the study.
Jennifer Logue, MD, from BHF Glasgow Cardiovascular Research Centre in Scotland, and colleagues tracked the health of more than 6,000 middle aged men with high cholesterol, but no history of diabetes or cardiovascular disease, for around 15 years.
After excluding men who had cardiovascular problems or died within two years of the start of monitoring, to correct for any bias, 214 deaths and 1,027 non-fatal heart attacks/strokes occurred during the whole period.
The risk of a heart attack was compared across categories of increasing body mass index (BMI), using two different approaches.
One simply corrected for any differences in the age or smoking status of the men, while the second corrected for cardiovascular risk factors such as high cholesterol and blood pressure, deprivation and any medications the men were taking.
The results showed that the higher a man's weight, the higher was his likelihood of having other risk factors for cardiovascular disease and of having a fatal heart attack. However, there was no increased risk of a non-fatal heart attack with increasing BMI (when using either approach).
In the model simply correcting for age and smoking, this risk was 75 percent higher. Despite correcting for known cardiovascular risk factors, medication and deprivation in the second model, the risk was still 60 percent higher.
"Inflammation is a strong factor in fatal cardiovascular disease, and obesity is increasingly being recognized as an inflammatory state, which may partly explain how obesity is linked to heart disease," said the authors, adding that it has implications for treatment and prevention.
"We have shown that obesity is associated with an increased risk of fatal coronary heart disease events after adjusting for classical cardiovascular risk factors, deprivation and confounding factors such as drugs," they concluded.
"This link was not seen for non-fatal coronary heart disease events and therefore, owing to large relative numbers of such events, also not seen for composite coronary heart disease events.
"In other words, our data suggest that obesity may give greater risk for fatal coronary heart disease events than non-fatal events, even after accounting for classical coronary heart disease risk factors."