The influence of BMI in asthma. Which traits are due to obesity and which to asthma and obesity phenotype?

Abstract

Background: Characteristics of the asthma and obesity phenotype have been described by cluster studies, but they have not been subsequently confirmed. Specific characteristics of this phenotype have not been differentiated from those inherent to the patient’s body mass index (BMI). Objectives: This study aims to assess the effect of BMI on asthma. This will allow to identify which traits could define the asthma and obesity phenotype, and which are inherent to the patient's BMI. Methods: A real-life retrospective observational study was conducted with a 2,514 patients database. Data was collected on the first visit to the Allergy clinic of all patients who underwent a correct spirometry maneuver due to suspected asthma between November 2014 and November 2017. All BMI, sex and age groups were represented. Results: BMI influence over asthma differed in different age groups and genders. All spirometric results and FeNO were influenced by BMI. Concerning asthma characteristics only a later asthma onset with higher BMI values was observed. No other differences were found between different BMI groups. Conclusions: The effect of BMI on asthma is age dependent, so it should be corrected for age. The most important variations are on FeNO and spirometric results. The specific characteristics of the asthma and obesity phenotype are a greater perception of symptoms with fewer alterations in respiratory function tests and a lower prevalence of atopy, rhinitis and allergy, including allergic asthma. Other characteristics of this phenotype, such as a higher women prevalence or being late-onset or non-eosinophilic asthma, are non-specific for this phenotype.