Overweight is not a comorbidity factor during childhood asthma: the GrowthOb study

Abstract

While being overweight is a risk factor for subsequent asthma in children, the importance of body mass index (BMI) as a comorbidity factor remains debated. The aim of this study was to assess the relationships between being overweight and the characteristics of childhood asthma.The BMI, BMI z-scores and International Obesity Task Force (IOTF) grades were evaluated in asthmatic children according to atopic status, symptoms during the past 3 months, exercise breathlessness, treatment and lung function in 6-15-yr-old children with confirmed asthma.491 asthmatic children (mean¡SD age 10.8¡2.6 yrs; 179 females) were prospectively enrolled. There were 78 (15.5%) overweight (IOTF grade 1) and eight (1.6%) obese (grade 2) children. The children's BMI z-scores did not differ according to atopy, exacerbation, symptom-free days or treatment. The BMI z-score correlated positively with forced vital capacity and forced expiratory volume in 1 s in females, which could be related to earlier puberty in overweight females (growth spurt with increased volumes). Compared with normal weight children, overweight and obese children had reduced lung volume ratios (functional residual capacity/total lung capacity (TLC) and residual volume/TLC), no evidence of airflow limitation and similar symptoms.In conclusion, the observed functional relationships with BMI are not specific to asthma and being overweight is not associated with significant clinical impacts on asthma during childhood.KEYWORDS: Body mass index, lung function, lung volumes, obesity, z-score I n the paediatric population, an increase in body mass index (BMI) is associated with the increased incidence [1] and prevalence [2] of asthma. The role of being overweight as a comorbidity factor is said to be ''possibly important, yet poorly studied '' [3]. Conflicting results on the relationship between BMI and asthma phenotype have been published. Being overweight has been associated with the severity of asthma exacerbations [4,5], as well as with poor asthma control [6]. However, in an important retrospective study, no effect of BMI on the time required to achieve control of asthma or on the ability to maintain good control of asthma was shown [7]. BMI per se has also been inconsistently correlated with clinical symptoms, such as coughing and wheezing on exertion [8], and with an increase in the number of symptom days and in the number of exacerbations in females only [9]. Such discrepancies between results might partially be due to the various cut-off points of BMI that are used across studies to define overweight and obesity (frequently the 85th or 95th percentiles). Normal values of BMI are age-and sex-specific throughout childhood; therefore, the transformation of children's BMI values into sex-and age-specific zscores is mandatory in order to ascertain the relationships between stoutness and clinical events and lung function. To further study the effect of overweight/obesity during childhood, the grades of COLE and co-workers [10,11] of the International Obesity Ta...

Monitoring asthma in childhood: lung function, bronchial responsiveness and inflammation

“…Specific airway resistance measured at preschool age correlated with subsequent FEF50%; therefore, predicting subsequent mild airflow limitation. In obese asthmatic children specific airway resistance measured by body plethysmography can be helpful in differentiating lung function changes due to asthma (elevated specific airway resistance) from those due to obesity (normal specific airway resistance) [57]. To date, there are no randomised controlled studies showing that body plethysmography is useful in routine monitoring of asthma in children.…”

Monitoring asthma in children

“…In selected cases, body plethysmography may be of help, particularly in the management of difficult and severe asthma [111]. In obese asthmatic children, measurements of specific airway resistance and lung volumes via body plethysmography may differentiate lung function changes due to asthma (elevated specific airway resistance and elevated total lung capacity) from those due to obesity (normal specific airway resistance) [112].…”

Review of different anthropometric and nutritional measurements in children with bronchial asthma

“…The increased BMI in these children has an impact on the disease as well [15,24,28]. As stated in a research by Holguin et al, 2011, obese children with BA are more likely to have continuous cough, sputum production, chest tightness, wheeze, dyspnea, nocturnal symptoms, and a reduced quality of life if compared to the children with normal BMI or overweight.…”

“…Similarly, they are more likely to have exacerbations, requiring oral steroids and the use of healthcare resources, including hospital visits, admissions in the Intensive care unit, and mechanical ventilation [24]. Obese and overweight children with BA tend to have reduced lung volume ratios (functional residual capacity/total lung capacity (TLC) and residual volume/TLC) [28]. Furthermore, the obese adolescents with BA have a higher prevalence of the metabolic syndrome than the obese adolescents without BA, more significantly in boys [11].…”