• High central adiposity was linked to elevated CV risk among people with normal BMI.
• In people with obesity, lower central adiposity may confer lower CV risk vs. those with more central adiposity.

Primary prevention of heart disease may be improved with the use of waist circumference or waist-to-height ratio rather than BMI to guide cardiovascular disease risk assessment, researchers reported.

Many people with otherwise normal BMI but more central adiposity may experience increased risk for CV events. Conversely, those with obesity based on their BMI but lower central adiposity may have lower CV risk compared with those with obesity and higher central adiposity, according to data published in the Journal of the American College of Cardiology.

“It is becoming more recognized that BMI is not a great measure of metabolic and CV risk. BMI is not a great measure of abdominal or visceral fat,” Michael J. Blaha, MD, MPH, professor of medicine at Johns Hopkins Medicine, told Healio. “Particularly in people who are the high end of normal weight or are overweight, there may be a large difference in risk based on the amount of abdominal/visceral fat. Waist circumference and waist-to-hip ratio are good measures of abdominal/visceral fat. When added to BMI, they provide a much better assessment of body composition.”

Using data from 24 prospective studies, researchers evaluated the rate of reclassification from normal weight, overweight and obesity based on BMI using measures of central adiposity. All participants with information on waist circumference or waist-to-height ratio were included in the analysis. Participants with BMI less than 18.5 kg/m² or with a history of coronary heart disease at baseline were excluded.

The researchers followed each of the 259,351 participants until one of nine outcomes of interest occurred: fatal or nonfatal MI, fatal or nonfatal stroke, heart failure, atrial fibrillation diagnosis, total CHD, total CVD, CHD mortality, CVD mortality and all-cause mortality.

High waist circumference was defined as more than 88 cm for women and more than 102 cm for men; high waist-to-height ratio was defined as more than 0.85 for women and more than 0.9 for men; and normal BMI was defined as 18.5 kg/m² to less than 25 kg/m², overweight was defined as 25 kg/m² to less than 30 kg/m² and obesity was defined as BMI of at least 30 kg/m², according to the study methods.

The researchers reported that among participants with normal weight per their BMI, 5% had high waist circumference and 18% had high waist to height ratio. Among participants with overweight per their BMI, 39% had high waist circumference and 40% had high waist-to-height ratio. Among participants with obesity per their BMI, 9% had low waist circumference and 45% had low waist-to-height ratio.

Risk for adverse outcomes associated with high waist circumference or high waist-to-height ratio ranged from 15% to 50% or more among participants with normal weight or overweight per their BMI, according to the study.

The researchers observed that among those with low waist circumference, there were no significantly different risks among participants with obesity compared with those with normal weight, except for lower all-cause mortality.

Women with obesity and low waist-to-height ratio had higher risk for all outcomes compared with women with normal weight and low waist-to-height ratio, a pattern not observed among men, researchers reported.

Moreover, among participants with obesity, 49% of HF events, 46% of AF events and 36% of CHD mortality were attributable to elevated waist circumference, according to the study.

“We are moving away from BMI as the single measure of weight and body composition. We are appreciating that body composition matters, particularly the amount of visceral fat, even when the weight/BMI is normal or only overweight,” Blaha told Healio. “Patients with normal weight or overweight can still have high metabolic and CV risk are appreciating this, and are moving toward defining obesity using a combination of BMI and/or multiple measure of abdominal fat like waist circumference and waist-to-hip ratio.”

Michael J. Blaha, MD, MPH, is professor of medicine and director of clinical research at the Ciccarone Center for the Prevention of Cardiovascular Disease at Johns Hopkins Medicine. Blaha can be reached at cardiology@healio.com.