Greater waist circumference was associated with a higher mortality risk independent of body mass index, according to a recent report.
Waist circumference is positively associated with mortality risk within all categories of BMI—normal, overweight, and obese. In fact, the relationship between greater waist circumference and higher mortality is strongest among women with a normal BMI, said Eric J. Jacobs, Ph.D., and his associates, who are with the epidemiology research program at the American Cancer Society in Atlanta.
The link between waist circumference and mortality has been reported in numerous studies, but this is the first study to examine that association within the standard categories of BMI, they noted (Arch. Intern. Med. 2010;170:1293-1301).
Dr. Jacobs and his colleagues used data from the Cancer Prevention Study II Nutrition Cohort, a large prospective study that obtained demographic, medical, and behavioral factors by self-administered questionnaire. They reviewed the findings on 48,500 men and 56,343 women aged 50 years and older in the 1990s who were followed through 2006. Almost all of the study subjects were white. The median baseline age was 67 years for women and 69 years for men.
The 14,647 deaths during follow-up included 5,410 cancer deaths, 4,942 cardiovascular deaths, 11,189 deaths resulting from respiratory disorders and 3,106 deaths from all other causes.
Any waist circumference greater than the smallest sizes (less than 90 cm in men or less than 75 cm in women) was associated with higher mortality. The mortality risk rose linearly with increasing waist circumference both in men and women.
Waist circumference was positively related to mortality in all patients. For men, the relative risk of mortality rose 16% (with normal BMI), 18% (overweight), and 21% (obese) with every 10-cm increase in waist size. For women, the relative risks with every 10-cm increase were greater for those with normal BMIs: 25% (normal), 15% (overweight), and 13% (obese).
When analyzed by cause of death, the link between waist circumference and mortality was strongest with death from respiratory causes, followed by cardiovascular disease and then cancer, Dr. Jacobs and his associates reported.
The investigators found no significant interactions between BMI-adjusted waist circumference and diabetes, smoking, or follow-up time. In addition, the researchers saw no interaction between waist circumference and hormone therapy in women. Relative mortality risks associated with waist circumference appeared to be greater in men who were less physically active.
“Results from this large prospective study emphasize the importance of waist circumference as a risk factor for mortality in older adults, regardless of whether the BMI is categorized as normal, overweight, or obese. Our results suggest that, regardless of weight, avoiding gains in waist circumference may reduce risk of premature mortality,” the researchers said.
The findings are important in light of the fact that current clinical guidelines do not address waist circumference in normal-weight patients and do not recommend weight loss for abdominally obese patients unless they have a high BMI, Dr. Jacobs and his associates noted.
The study was limited in that it included participants who were at least 50 years old, and it included very few nonwhite subjects. Thus, “results may not be generalizable to younger populations or those of other racial or ethnic backgrounds,” the authors noted.