Effect of Weight Reduction on Respiratory Function and Airway Reactivity in Obese Women

Shawn D. Aaron, MD, MSc; Dean Fergusson, PhD; Robert Dent, MD; Yue Chen, PhD; Katherine L. Vandemheen, BScN; Robert E. Dales, MD, MSc

Disclosures

CHEST. 2004;125(6) 

In This Article

Abstract and Introduction

Background: Population-based studies have documented an association between obesity and an increased prevalence of asthma in women.
Methods: We prospectively studied 58 obese women with a body mass index of > 30 kg/m2, 24 of whom had asthma, who were enrolled in an intensive 6-month weight loss program to determine whether loss of body mass would be correlated with improvements in bronchial reactivity, lung function, and disease-specific health status.
Results: Patients lost an average of 20 kg over the 6-month period. For every 10% relative loss of weight, the FVC improved by 92 mL (p = 0.05) and the FEV1 improved by 73 mL (p = 0.04), however, bronchial reactivity did not significantly change with weight loss (p = 0.23). Patients who lost > 13% of their pretreatment weight experienced improvements in FEV1 (p = 0.01), FVC (p = 0.02), and total lung capacity (p = 0.05) compared to patients in the lowest quartile who failed to lose significant amounts of weight. Neither group experienced any significant change in methacholine responsiveness (p = 0.57). Patients who completed the 6-month weight loss program experienced improvements in respiratory health status, irrespective of weight loss.
Conclusion: We concluded that weight loss can improve lung function in obese women, however, the improvements appear to be independent of changes in airway reactivity.

The prevalence of obesity has increased worldwide to reach epidemic proportions in many industrialized countries.[1] Recent cross-sectional studies have suggested that there exists a significant association between obesity and asthma in women. A Canadian population-based study[2] showed that the adjusted odds ratio for asthma was 1.52 in obese women compared to nonobese women. Population-based studies in the United Kingdom[3] and the United States[4,5] have yielded similar results, suggesting an increased prevalence of asthma among Canadian, British, and American obese women.

One controlled clinical trial[6] randomized 38 obese asthmatic subjects to an 8-week supervised weight reduction program or to a control program. Patients in the weight-reduction group significantly improved their FEV1 and FVC values relative to control subjects. Similarly, they improved their health status, as measured by a disease-specific quality-of-life questionnaire, relative to control subjects. However, this study did not evaluate methacholine responsiveness or other measures of airway reactivity associated with asthma. Therefore, it is unclear whether the observed improvement in lung function and respiratory health status was due to an improvement in asthma and airway reactivity per se, or due to a reduction in mass-loading of the respiratory system that occurs following significant weight reduction.

The overall aim of this study was to determine whether a relationship exists between changes in body weight and airway reactivity in overweight women. We studied 58 women with a body mass index (BMI) of > 30 kg/m2 to determine the following: (1) whether loss of body mass improves lung function in these subjects; and (2) whether this may be correlated with improvements in bronchial reactivity.

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