Characterisation of Asthma in Obese Subjects

Characterisation of Asthma in Obese Subjects. Relationships Between Asthma and Obesity, Potential Mechanisms by Which Obesity Can Contribute to Asthma and Modify Treatment Responses

Our hypothesis:

Obese subjects with a physician's made diagnosis of asthma have a poorer asthma control than asthmatics with normal weight, less variability of peak expiratory flows (PEF) and bronchodilator response,increased induced sputum and systemic markers of inflammation and an increased prevalence of atopy.

Obese subjects have an increased incidence of co-morbidities such as rhinosinusitis, gastroesophageal reflux and sleep apnea syndrome.

This study aims to determine if, in comparison with asthmatics with a normal weight, paired for age and sex, obese subjects with asthma (all not using anti-inflammatory agents) show:

• A more uncontrolled asthma, increased health care use and poorer quality of life
• A reduced response to bronchodilators and diurnal variability of expiratory flows
• More marked airway inflammation and evidences of a systemic inflammatory response
• An increased prevalence of co-morbidities which can influence the report of respiratory symptoms or the severity of the disease, such as esophageal reflux symptoms, upper airway disease (rhinitis) and sleep apnea syndrome or other sleep disorder.

Questionnaires on respiratory symptoms, health care use, quality of life, medication and asthma control will be administered and a thoracic examination performed.

Spirometry and bronchodilator response, blood tests for inflammatory parameters, pH measurements in exhaled air condensate and sputum induction will be performed. Peak expiratory flows will be measured and recorded on a diary card during one week.

On the second visit, measures of lung volumes and a methacholine challenge will be performed.

Inclusion Criteria:

• aged 18 and over.
• in good health apart from asthma or obesity as determined by history and physical examination (no other condition which could influence the proposed tests).
• All will be non smokers or ex- smokers for more than six months with a smoking history of no more than 10 pack- years (i.e., one pack per day or its equivalent for 10 years.)
• Subjects will have a physician's made diagnosis of asthma and have received a bronchodilator prescription in the last year.

Exclusion Criteria:

• Use of asthma medications other than bronchodilators
• Subjects who are, in the opinion of the investigator, mentally or legally
• incapacitated thus preventing informed consent from being obtained.
• Subjects having a co-existing illness that precludes them from the trial.
• Pregnancy or lactation