A study led by a Loyola University Health System researcher found that the larger a kidney patient’s waist circumference, the greater the chance the patient would die during the course of the study.
The study by lead researcher Holly Kramer, MD, MPH, and colleagues was published in the American Journal of Kidney Diseases.
Waist circumference was more strongly linked to mortality than another common measure of obesity, body mass index (BMI).
BMI is a height-to-weight ratio. For example, if John and Mary are both the same height, but John weighs 20 pounds more, then John will have a higher BMI than Mary. But BMI can be misleading — a muscular person with little body fat could have a BMI higher than a flabby person with little muscle mass. Waist circumference, by contrast, simply measures abdominal fat.
Researchers examined data from 5,805 adults age 45 and older who had kidney disease and participated in a study called REGARDS (Reasons for Geographic and Racial Differences in Stroke). They were followed for a median of four years and during that time 686 kidney patients (11.8 percent) died.
The average BMI of the kidney disease patients who died was 29.2. This was lower than the average BMI, 30.3, of the patients who survived. (A BMI between 25 and 29.9 is considered overweight, while a BMI of 30 and above is obese.)
By contrast, the kidney patients who died had a larger average waist circumference (40.1 inches) than the patients who survived (39.1 inches.)
Researchers compared kidney disease patients with large waists to patients who had more normal waist sizes. After adjusting for BMI and other risk factors, women with waists equal to or greater than 42.5 inches and men with waists equal to or greater than 48 inches were 2.1 times more likely to die than those with trimmer waists (less than 31.5 inches for women and less than 37 inches for men).
Researchers concluded that in adults with kidney disease, BMI by itself may not be a useful measure to determine mortality risks associated with fat. The reason is that BMI reflects several components, including muscle mass and abdominal fat.
“In contrast,” the researchers conclude, “waist circumference reflects abdominal adiposity [fat] alone and may be a useful measure to determine mortality risk associated with obesity in adults with chronic kidney disease, especially when used in conjunction with BMI.”
Kramer is an associate professor in the Department of Medicine, Division of Nephrology at Loyola University Chicago Stritch School of Medicine. Her co-authors are David Shoham, PhD, and Ramon Durazo-Arvizu, PhD, of the Department of Preventive Medicine and Epidemiology at Loyola University Chicago Stritch School of Medicine; Leslie McClure, PhD, George Howard, DrPH , Suzanne Judd, PhD, Paul Muntner, PhD, Monika Safford, MD, and David Warnock, MD, of the University of Alabama at Birmingham; and William McClellan, MD, MPH of Emory University.
Based in the western suburbs of Chicago, Loyola University Health System is a quaternary care system with a 61-acre main medical center campus, the 36-acre Gottlieb Memorial Hospital campus and 22 primary and specialty care facilities in Cook, Will and DuPage counties. The medical center campus is conveniently located in Maywood, 13 miles west of the Chicago Loop and 8 miles east of Oak Brook, Ill. The heart of the medical center campus, Loyola University Hospital, is a 569-licensed-bed facility. It houses a Level 1 Trauma Center, a Burn Center and the Ronald McDonald® Children’s Hospital of Loyola University Medical Center. Also on campus are the Cardinal Bernardin Cancer Center, Loyola Outpatient Center, Center for Heart & Vascular Medicine and Loyola Oral Health Center as well as the LUC Stritch School of Medicine, the LUC Marcella Niehoff School of Nursing and the Loyola Center for Fitness. Loyola’s Gottlieb Memorial Hospital campus in Melrose Park includes the 264-bed community hospital, the Gottlieb Center for Fitness and the Marjorie G. Weinberg Cancer Care Center.