Obesity and asthma: a specific phenotype?

Chest. 2008 Aug;134(2):317-323. doi: 10.1378/chest.07-2959. Epub 2008 Jul 18.


Background: Obesity is associated with an increased prevalence of asthma, especially in women, and appears to be more severe in the obese. This study aimed to determine if obese subjects have a specific asthma phenotype.

Methods: Forty-four consecutive obese subjects (body mass index [BMI] > or = 30 kg/m(2)) and 44 consecutive nonobese subjects (BMI < 25 kg/m(2)), all with asthma, completed an asthma control questionnaire, and underwent methacholine challenge with symptom perception scores, and sputum induction for differential cell count. BMI, waist circumference, and waist-to-hip ratio also were measured.

Results: Despite similar expiratory flows, bronchodilator response, airway responsiveness to methacholine, and symptom perception scores, asthma control was poorer in obese subjects than in nonobese subjects (p = 0.005). Total lung capacity (p = 0.01), expiratory reserve volume (p < 0.0001), functional residual capacity (p < 0.0001), and residual volume (p = 0.006) were lower in obese subjects than in nonobese subjects. Induced-sputum eosinophil and neutrophil counts were similar in both groups, although there was an inverse correlation between sputum eosinophils and waist circumference and a trend for a similar relationship for BMI. Blood serum C-reactive protein (p = 0.009) and fibrinogen (p = 0.0004) levels were higher in obese subjects than in nonobese subjects.

Conclusion: Obese people with asthma had poorer asthma control than nonobese asthmatics despite similar symptoms perception. Bronchial and systemic inflammatory characteristics and the specific pattern of pulmonary function changes suggest a different phenotype of asthma in these subjects.

Trial registration: Clinicaltrials.gov Identifier: NCT00532363 and NCT00532831.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Asthma / etiology
  • Asthma / physiopathology*
  • Asthma / prevention & control*
  • Body Mass Index
  • Bronchial Provocation Tests
  • Bronchodilator Agents / therapeutic use
  • Case-Control Studies
  • Female
  • Forced Expiratory Volume / physiology
  • Humans
  • Male
  • Middle Aged
  • Obesity / complications*
  • Obesity / physiopathology*
  • Phenotype
  • Total Lung Capacity / physiology


  • Bronchodilator Agents

Associated data

  • ClinicalTrials.gov/NCT00532363
  • ClinicalTrials.gov/NCT00532831