Body mass index (BMI) doesn’t predict cardiovascular risk as well as waist-to-height ratio and other measures of obesity, new research suggests.
Asked whether physicians should replace BMI as a way of assessing a patient’s cardiovascular risk, the study’s lead author Dr. Harald J Schneider responded by email, “Probably, yes. However, I would still be cautious.”
He pointed out that BMI might still be useful for assessing other risks, such as for orthopedic complications of being overweight or obese, which were not considered in the current study.
Dr. Schneider, of Ludwig-Maximilians University in Munich, Germany, and his colleagues analyzed data from two German cohort studies called DETECT and SHIP. DETECT followed 6,355 patients for more than 3 years, and SHIP followed 4,297 patients for more than 8 years. They reported their findings online February 3rd in the Journal of Clinical Endocrinology and Metabolism.
Overall, 620 people in both studies died, with 181 deaths attributed to cardiovascular causes, and 325 reached the composite endpoint of stroke, heart attack or cardiovascular death.
In both studies, the waist-to-height ratio was the best predictor of cardiovascular mortality, all-cause mortality and the combined endpoint.
The relative risk of cardiovascular mortality in the highest quartile of waist-to-height ratio compared to the lowest quartile was 2.75.
For BMI, the RR in the highest quartile versus the lowest quartile was 0.74.
Both waist-to-height ratio and waist circumference were significant predictors of all-cause mortality, and all measures except BMI were significantly correlated with the composite endpoint.
Results were comparable when subjects were stratified by age and gender.
“BMI does not distinguish between visceral fat, the ‘bad’ fat that accumulates in the belly, and subcutaneous fat, the ‘good’ fat that is under the skin,” Dr. Schneider told Reuters Health.
He did point out that these studies involved mostly white, European populations, making it difficult to apply the same conclusions to other ethnic groups.
Dr. Cora E. Lewis, of the Division of Preventive Medicine at the University of Alabama at Birmingham, said other research has similarly indicated that it is more useful to know about abdominal fat than BMI when it comes to cardiovascular risk assessment. She was not involved in Dr. Schneider’s research.
“There are some limitations to BMI, but it is easy to obtain,” she said in an e-mail. “If you really want a measure to be widely used, the staff at the doctor’s office needs to be able to do it quickly and reliably without a lot of fuss from the patients.”
She added that the National Heart, Lung and Blood Institute’s guidelines for assessing obesity and heart risks do advise the use of waist circumference as well as BMI.
In Dr. Schneider’s study, waist circumference was not as successful at predicting risk as waist-to-height ratio, but it appeared to be better than BMI.
“Given that BMI does capture a lot of the information, I am not betting against BMI, at least in the near future,” Dr. Lewis said.
J Clin Endocrinol Metab 2010.
From Reuters Health Information