No matter what a patient's body mass index (BMI) or weight, his or her risk of dying for any reason after the 50th birthday greatly increases if waist circumference is abnormally high, 88 cm (34.64 inches) in women or 102 cm (40.16 inches) inches in men. That holds especially true for women.
That's the finding of research published this month by researchers for the American Cancer Society in Atlanta, who suggest that clinicians and policymakers might revisit their guidelines that define who is overweight in America. The authors say they believe their study is the first to scrutinize the link between waist circumference and mortality in each of three standard categories of BMI: normal, overweight and obese."
"In our study, waist circumference was positively associated with risk of mortality among individuals within all (three) categories of BMI examined," they wrote. "The relative risks associated with a 10-cm increase in waist circumference ranged from approximately 15% to 25% within various categories of BMI, with the strongest association observed among women in the normal BMI category."
The authors suggest that clinicians evaluate waist circumference even in patients who are not overweight. "Currently available clinical guidelines from the National Institutes of Health are based on evidence from the 19990s (which) recommend that waist circumference be used to identify increased disease risk only among individuals in the overweight and obese categories of BMI (greater or equal to 30)," they wrote.
"But they do not specifically recommend weight loss goals for abdominally obese patients (waist circumference of 88 cm or more in women or 103 cm in men) who are in the normal or overweight BMI category unless they also have two or more cardiovascular risk factors or a desire to lose weight."
The researchers, including epidemiology researcher Eric J. Jacobs and colleagues at the Atlanta ACS, could not say for sure what might be causing the higher mortality rates. However, large waist circumference, also known as being shaped like a pear, has been associated with inflammatory processes, insulin resistance, diabetes, abnormal cholesterol levels and heart disease, according to other research.
Another explanation might be that higher amount s of adipose tissue surrounding the viscera or organs in the abdomen, is for some reason more dangerous than having fat tissue under the skin, the researchers suggested.
In their paper, the researchers said that higher death rates were most closely linked to higher waist circumference measurements in patients with respiratory disease, followed by cardiovascular disease and cancer.
The researchers said their study is particularly valuable because it ranked participants on the basis of their waist circumference in 5 or 10 centimeter increments, rather than grouping them in quintiles, so the result scan be more easily applied to other populations, the researchers wrote.
The study looked at waist circumference and mortality among 48,500 men and 56,343 women, all over age 50, who were part of the Cancer Prevention Study II Nutrition Cohort. The cohort, the second in a series, was launched to examine the impact of environmental and lifestyle factors on cancer etiology. During the study period of nine years, 15,000 participants in the cohort died.