Abdominal obesity is a strong independent risk factor for heart disease, and using the waist-hip ratio rather than waist measurement alone is a better predictor of heart disease risk among men and women, researchers reported in a study published in Circulation: Journal of the American Heart Association.
In the study, researchers also looked at whether the association between fat distribution and heart disease risk was independent of body mass index (BMI), which assesses body weight relative to height, as well as other heart disease risk factors, such as high blood pressure and high cholesterol.
"The size of the hips seems to predict a protective effect," said Dexter Canoy, M.Phil., M.D., Ph.D., lead author of the study and a research fellow in epidemiology and public health at the University of Manchester in the United Kingdom. "In other words, a big waist with comparably big hips does not appear to be as worrisome as a big waist with small hips."
The research was based on 24,508 men and women ages 45 to 79 in the United Kingdom who participated in the European Prospective Investigation into Cancer cohort study (EPIC-Norfolk) which is based at the University of Cambridge in the UK. Researchers measured participants' weight, height, waist circumference, hip circumference and other heart disease risk factors from 1993 to 1997. They then followed up with participants for an average 9.1 years.
During the follow-up, 1,708 men and 892 women developed coronary heart disease. When they divided the men and women into five groups, according to waist-hip ratio, researchers found that those with the highest waist-to-hip ratio had the highest heart disease risk. Among the findings:
- Men in the top one-fifth of the distribution (those with the biggest waists in relation to their hips) had a 55 percent higher risk of developing coronary heart disease compared to men in the bottom one-fifth of the distribution (those with the smallest waists in relation to their hips).
- Women in the top one-fifth, or the highest waist-to-hip ratio group, were 91 percent more likely to develop heart disease than women with the smallest waists in relation to their hips.
- Waist-only measurements underestimated heart disease risk by 10 percent to 18 percent when compared to risk estimates for waist measurements when hip is considered (waist-to-hip ratio).
- When waist-only, body mass index and coronary heart disease risk factors are considered, for every 6.4 centimeter (cm) increase in hip circumference in men and for every 9.2 cm hip circumference increase in women, there is a 20 percent lower risk for developing heart disease.
The study's results are definitive for predicting risk in relatively healthy men and women in the general population, Canoy said. More research is needed on whether abdominal fat distribution is an independent risk factor for heart disease among people who have chronic and other diseases at baseline.
"People whose abdominal fat puts them at higher risk for heart disease do not always appear overweight or obese," Canoy said. "However, the overriding message from this and other studies about heart disease risk is that, despite the different measures and risk estimates, the bottom line is that many of us need to lose excess weight. Doctors should start looking beyond weight, height, simple waist circumference and BMI to assess heart disease. A simple waist-hip ratio measurement is a strong predictor of heart disease."
The EPIC-Norfolk study is funded by the Cancer Research UK, Medical Research Council, Stroke Association, British Heart Foundation, Department of Health, Europe against Cancer Programme Commission of the European Union, Food Standards Agency and Wellcome Trust. Canoy was funded by Cambridge Commonwealth Trust/Cambridge Overseas Trust and Christ's College.
Canoy worked with collaborators from Cambridge University. Co-authors are: S. Matthijs Boekholdt, M.D., Ph.D.; Nicholas Wareham, M.B.B.S., FRCP; Robert Luben, B.Sc.; Ailsa Welch, Ph.D.; Sheila Bingham, Ph.D.; Iain Buchan, M.D., F.F.P.H.; Nicholas Day, Ph.D., F.R.S.; and Kay-Tee Khaw, M.B.B.Chir., FRCP.
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