Association of body mass index with airway hyperresponsiveness and lung function in adult asthmatics

Abstract

Purpose: Obesity is commonly regarded as a risk factor for asthma development, poor asthma control, and poor response to asthma therapy. However, its relationships are not always consistent. Gender difference has been reported to influence asthma severity and asthma control. We investigated the contribution of obesity to airway hyperresponsiveness (AHR) and lung function before and after treatment in adult asthmatics. Methods:The medical records of a total of 323 adult asthmatics were analyzed retrospectively. Asthma was diagnosed based on the positive result of methacholine bronchial provocation test (PC20 ≤ 25 mg/mL) or bronchodilator test (≥ 12% and 200-mL improvement in forced expiratory volume in 1 second after inhalation of a bronchodilator). Follow-up spirometry was performed in 113 patients after at least 3 months of asthma treatment with controller medication. Percent change between spirometry before and after treatment was defined as {[(value after treatment-value before treatment)/value before treatment] × 100}. Body mass index (BMI, weight [kg]/height [m 2 ]) was categorized into underweight (< 18.5), normal weight (18.5-24.9), overweight (25.0-29.9), and obese (> 30) according to the world health organization classification. Results: BMI did not show any significant correlation with PC20 value of methacholine provocation test and each lung function parameter before and after treatment. When we divided the study subjects according to gender and age, BMI was negatively correlated with PC20 value only in female adult asthmatics under 65 years old (r= -0.024, P= 0.036). Conclusion: Obesity is positively correlated with the intensity of AHR in female adult asthmatics. Gender seems to differentially contribute to the relationship between BMI and AHR. (Allergy Asthma Respir Dis 2014;2:16-22