Published: Nov 11, 2013 | Updated: Nov 12, 2013
By Elizabeth DeVita Raeburn, Contributing Writer, MedPage Today

Full Story:  http://www.medpagetoday.com/Cardiology/MyocardialInfarction/42839

Being overweight or obese were risk factors for myocardial infarction (MI) and ischemic heart disease (IHD), even in the absence of metabolic syndrome, researchers found.

Among participants with and without metabolic syndrome, there were “increasing and cumulative incidences” of both MI and IHD along the continuum of weight from normal to obese (log-rank trend P=0.006 and P<0.001 respectively), according to Borge G. Nordestgaard, MD, DMSc, and his co-author, Mette Thomsen, MD, both of Copenhagen University Hospital.

In participants without metabolic syndrome, the hazard ratios for MI compared with normal weight participants were 1.26 (95% CI, 1.00-1.61) in overweight individuals and 1.88 (95% CI, 1.34-2.63) in those who were obese, they wrote online in JAMA Internal Medicine.

The hazard ratios for MI among those with metabolic syndrome were 1.39 (95% CI, 0.96-2.02) in those of normal weight, 1.70 (95% CI, 1.35-2.15) in the overweight, and 2.33 (95% CI, 1.81-3.00) in obese participants.

“For IHD, results were similar but attenuated,” the authors wrote, possibly because the diagnostic criteria for IHD include subjective symptoms of angina pectoris, which could have resulted in misclassification. Overall, the findings suggest that “metabolic syndrome is no more valuable than BMI in identifying individual risk,” the authors wrote.

The study included 71,527 people enrolled in the Copenhagen General Population Study for whom BMI, waist measurement, blood pressure and biochemical analyses, which allowed for identification of metabolic syndrome, were available.

Participants were divided into three categories of BMI: normal, with a BMI of 18.5 to 24.9; overweight, with a BMI of 25.0 to 29.9; and obese, with a BMI of at least 30. Median follow-up was 3.6 years.

The findings “add important new evidence to counter the common belief in the scientific and lay communities that the adverse health effects of overweight are generally inconsequentialas long as the individual is metabolically healthy,” wrote Chandra L. Jackson, PhD, MS, andMeir J. Stampfer, MD, DrPh, of the Harvard School of Public Health, in an accompanying editorial.

The association between metabolic syndrome and ischemic heart disease is well established. But whether excess body fat leads to excess cardiovascular risk in the absence of metabolic syndrome has been controversial, wrote Nordestgaard and Thomsen.

This is partly due to conflicting study results in overweight or obese individuals without metabolic syndrome with regard to risk for MI and IHD. Some of these studies, Nordestgaard and Thomsen wrote, have led to “suggestions that overweight and obesity in these individuals are benign conditions.”

One explanation for the results, they said, is that abdominal obesity often precedes the other components of metabolic syndrome, and may even cause some of the other cardiovascular risk factors. This study, they said, may have captured overweight and obese individuals “at baseline,” before they went on to develop metabolic syndrome.

Those overweight or obese individuals in the study with metabolic syndrome, said Jackson and Stampfer, might have simply included “individuals at more advanced stages along the continuum of the pathological process.”

Findings in a recent Australian study of 4,056 adults support this hypothesis, they said. In that study, a large number of metabolically healthy obese participants went on to develop metabolic syndrome in the follow-up period, especially if they had a high baseline waist circumference.

Among the study’s limitations was that fasting plasma glucose and triglyceride measurements weren’t available, so the definition of metabolic syndrome had to be modified to allow nonfasting measurements. And there might have been residual confounding due to variation within each BMI category.

Patients were recruited from the general population, and selection bias might have existed in the form of over- representation of relatively healthy and overweight and obese individuals.

The cohort in this trial was also exclusively white and Danish, and the results may not be applicable to other races and countries, the authors said. The researchers also did not have specific information regarding the type or dose of lipid-lowering therapy that participants received during the study.

From the American Heart Association:

• Population-Based Prevention of Obesity: Comprehensive Promotion of Healthful Eating, Physical Activity, and Energy Balance
• Cardiovascular Risk in Asymptomatic Adults

Primary source: JAMA Internal Medicine