By Megan Rauscher Fri Jan 26, 2007

NEW YORK (Reuters Health) – In a study of normal-weight, overweight and obese adults, researchers found that waist circumference was consistently negatively associated with lung function across all weight categories.

Study chief Dr. Yue Chen of the University of Ottawa told Reuters Health that waist circumference is a better predictor of lung impairment than body mass index (BMI) — a measure of weight in relation to height used to determine how thin or fat a person is.

Obesity is associated with a wide range of health problems including respiratory dysfunction. “In our previous studies, we have found that obesity is associated with asthma and chronic obstructive pulmonary disease, and BMI is an important predictor,” Chen said.

In the current study, Chen and colleagues determined the predictive value of waist circumference and BMI for lung function in 1,674 normal-weight, overweight, or obese adults.

They report in the American Journal of Clinical Nutrition that waist circumference was negatively associated with several standard measures of lung function and the associations were unchanged by sex, age or BMI category (normal-weight, overweight and obese).

On average, a 1-cm increase in waist circumference was associated with a 13-mL reduction in “forced vital capacity” — a measure of the total lung volume of air that can be exhaled — and an 11-mL reduction in “forced expiratory volume in 1 second” — the maximum volume of air expired in 1 second.

In contrast, a negative association between BMI and lung function was observed only in adults who were overweight or obese.

These results show that waist circumference as a measure of abdominal fat has a somewhat more consistent predictability for lung function, the researchers conclude.

SOURCE: American Journal of Clinical Nutrition, January 2007.