Relationships between respiratory diseases, allergic sensitization, pulmonary function, and obesity in healthy schoolchildren

PURPOSE: The prevalences of asthma and obesity in childhood increased in the last years. Aim of the present study was to investigate the relationships between body weight and respiratory diseases, allergic sensitization, and pulmonary function in a sample of schoolchildren of Palermo, South Italy. METHODS: We studied 2150 schoolchildren (1059 males, 49.3%), randomly selected from 16 junior high schools, aged 10-17 years. Each of them fulfilled a respiratory questionnaire and performed spirometry, and skin prick tests (SPT) for more common allergens in the Mediterranean area. Atopy was defined as at least a positive (3 mm mean wheal diameter) SPT. Height and weight were measured in all the children and the body mass index (BMI) was computed as weight/height2 (kg/m2). Subjects were divided in 4 classes by the following BMI cut-off levels: 18.5, 25, and 30 kg/m2. RESULTS: Asthmatics (doctor diagnosed asthma - A) were 258 (12.0%); rhinitics (positive answer to the question "Have you ever had sneezing, or runny, or blocked nose apart from common cold or flu in the last 12 months?" - R) were 673 (31.3%); control subjects (C) were 1219 (56.7%). On the basis of BMI classes, subjects' distribution was 29.9%, 52.1%, 14.0%, and 4.0% respectively. Atopy prevalence was 40.1% in the whole sample, and 61.9%, 42.1%, and 34.3% among A, R, and C respectively (p<0.0001). The prevalence of A in the four BMI classes was 9.3%, 11.3%, 17.6%, and 20.9% respectively (p=0.0007). Similarly, atopy prevalence ranged from 36.9% to 52.3% (p=0.02) among BMI classes. Pulmonary function, evaluated by FEV1/FVC%, was significantly impaired in subjects with higher BMI (p<0.0001). In a logistic model, when corrected for confounding variables, a BMI>25 kg/m2 was an independent predictor of both asthma and decreased FEV1/FVC%. CONCLUSION: The present study points out that, in children, an increased body weight is an independent determinant of asthma and decreased respiratory function. CLINICAL IMPLICATIONS: Mechanisms underlying the relationships between childhood asthma and obesity remain to be understood.