COLORADO SPRINGS — Marginally increased waist circumference is strongly associated with prevalent hypertension in normal-weight and overweight adults, according to data from a large National Institute of Neurological Disorders and Stroke-sponsored study.
The finding is likely to change both clinical practice and guidelines, Dr. Deborah A. Levine predicted in reporting the results at a conference of the American Heart Association.
“As a practicing general internist, I do not routinely measure waist circumference as well as I should,” conceded Dr. Levine of Ohio State University, Columbus. “And I certainly don't do it in persons with normal [body mass index] at this time. But these data have prompted me to reconsider that practice.”
Moreover, the new data indicate a need to revise current U.S. guidelines regarding how waist circumference measurement is used as a cardiovascular risk assessment tool.
Current NIH guidelines include a less-than-forceful recommendation to consider measuring waist circumference—a guide to central adiposity—in individuals with normal BMIs. But the new data presented by Dr. Levine indicate that waist circumference measurement is a valuable indicator of risk in patients with normal BMIs.
The U.S. guidelines define normal waist circumference as less than 80 cm in women and 94 cm in men, and elevated waist circumference as more than 88 and 102 cm, respectively. The middle zone of marginally elevated values—80–88 cm in women and 94–102 cm in men—is a gray area that's largely disregarded by physicians and researchers alike. But this needs to change.
“Our data suggest that we should be treating waist circumference as a continuous risk factor and not a categorical variable where the middle category is actually ignored in practice and in studies,” Dr. Levine said.
In light of the new findings, she said, the current International Diabetes Federation guidelines make far more sense. In the IDF guidelines on metabolic syndrome, the group defines any waist circumference that's above normal as elevated, period.
Dr. Levine presented an analysis of waist circumference and prevalent hypertension in 21,351 black and white adult community-dwelling participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a population-based study whose primary goal is to identify explanations for the excess stroke mortality in the so-called “stroke belt” in the southeastern United States.
The prevalence of baseline hypertension was 45% among participants with a normal BMI, 56% in those who were overweight, and 66% in subjects with class I obesity.
After adjustment for numerous demographic factors as well as alcohol and tobacco use, physical activity, and glomerular filtration rate, a marginally increased waist circumference—that is, 80–88 cm in women and 94–102 cm in men—was independently associated with a 58% higher hypertension prevalence in normal-weight individuals and a 31% higher hypertension prevalence in those who were overweight, compared with participants with comparable BMI values but normal waist circumference.
An elevated waist circumference was associated with a 2.1-fold increased hypertension prevalence in normal-weight subjects, a 1.6-fold increase in those who were overweight, and a 48% increase in REGARDS participants who were obese class I.
As expected, a marginally increased waist circumference did not confer significantly increased risk of hypertension in obese subjects; it's known that waist circumference has a diminished ability to independently predict cardiovascular risk factors and morbidity in obese individuals.
ELSEVIER GLOBAL MEDICAL NEWS
“We should be treating waist circumference as a continuous risk factor and not a categorical variable” that goes ignored, Dr. Deborah A. Levine said. ©Andrea Reinaker