New From WOSCOPS: Obesity Independently Associated With CHD Death

February 16, 2011

February 16, 2011 (Glasgow, Scotland) — A new analysis of the landmark West of Scotland Prevention Study(WOSCOPS)has shown, for the first time, that obesity per se is associated with an increased risk of coronary heart disease (CHD) death [1]. Dr Jennifer Logue (University of Glasgow, Scotland) and colleagues report their findings online February 14, 2011 in Heart.

Logue told heartwire there are already a number of studies relating body-mass index (BMI) to risk of CHD events, "but it has always been presumed that this is due to traditional risk factors. When people have adjusted for those factors in the past, looking at total events, the risk is gone. But because we had a high number of events, we were able to separate them into fatal and nonfatal. Even after adjusting for all traditional cardiovascular risk factors, any confounding such as medication use and socioeconomic deprivation, we still had a 60% increased risk for fatal CHD events in men with a BMI of 30 and above."  

There seems to be something extra happening, that's the crux of it.

"There seems to be something extra happening, that's the crux of it," she says, but adds that more work is needed to confirm these findings in other data sets and to see whether they extend to other age groups, ethnic minorities, and women, because the WOSCOPS participants were middle-aged, white men from Scotland. Also there was far less obesity when this study was conducted compared with nowadays, so a more contemporary, "generally more obese cohort to try to power this would be helpful," she observes. 

Cause Could Be Inflammation or Structural Changes in the Heart

In WOSCOPS, after researchers excluded anyone with any event in the first two years, 1027 nonfatal and 214 fatal CHD events occurred during 14.7 years of follow-up, Logue et al explain.

They compared two models adjusting for confounding factors--one included only age and statin treatment, while the other included all known CVD risk factors plus deprivation--with a BMI of 25 to 27 kg/m2 as the reference group.

The risk of nonfatal events was similar across all BMI categories in both models. But the risk of fatal CHD events was increased in men with a BMI of 30 to 39.9 kg/m2in both the minimally adjusted model (hazard ratio 1.75; 95% CI 1.12–2.74) and the maximally adjusted model (HR 1.6; 95% CI 1.02–2.53).

"Our analysis suggests that white men with an increased BMI may have an increased risk of fatal CHD events beyond that mediated by classical risk factors," say the researchers.

They add that their research indicates the importance of investigating fatal and nonfatal events separately, "rather than assuming a common etiology," with the question still unanswered as to whether the nature of the event "differs only in severity or whether there are subtle differences in underlying mechanisms that lead to fatal events vs nonfatal outcomes."

And Logue says they have a number of theories as to what might be causing this increased risk. First, it could be due to an association of obesity with inflammation, she says, "because a previous analysis of the PROSPER study [2] has shown that inflammatory markers seemed only to affect fatal and not nonfatal events."

Also, recent studies suggest that larger people might have structural problems with the heart as a result of obesity, possibly leading to a higher risk of arrhythmias when the heart is ischemic and a consequent greater risk of sudden death or heart attack, she says.

Don't Ignore Obesity

Logue says that the importance of counseling on weight loss must be reiterated to the medical profession. "Weight is an easy thing to try to ignore because we don't have any simple way of dealing with it, and if we did we would be doing it. But doctors can't be doing cardiovascular risk assessments, checking BP and cholesterol, and telling people to stop smoking, and end it there. We need to find ways to help people lose weight."

Weight is an easy thing to try to ignore because we don't have any simple way of dealing with it.

And although it remains to be shown whether losing weight would make a difference to this increased risk of fatal CHD (which could, for instance, be irreversible), she stresses the many, already-proven global benefits of weight loss.

"We need to throw every spare penny we've got at trying to prevent people getting into that situation in the first place; these new results further highlight the urgent need for obesity-prevention strategies and evaluation of cardiovascular outcomes after effective interventions."

The authors declare they have no conflicts of interest. The original WOSCOPS was funded by Bristol-Myers Squibb and the first five years of posttrial follow-up were funded by Bristol-Myers Squibb and Sankyo.

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