Background: Because asthma preferentially burdens persons with atopy, atopy is simplistically considered a primary ‘cause’ of asthma. Yet at the population level, the percentage of asthma cases ‘attributable’ to atopy ranges from less than 10% to more than 60%. Seeking to understand the rationale for the variability of atopy-attributable cases of asthma, we systematically reviewed the results of our own previous epidemiological studies and several studies conducted by others in children. Methods: From each of the 37 random pediatric populations selected by a Medline search combining the key words ‘IgE or skin tests or hypersensitivity, immediate’ with ‘epidemiological studies, cross-sectional, case-control, prevalence, longitudinal, epidemiology of asthma’ (12 from our previous pediatric surveys and a further 25 reported from 19 studies in children), we extracted the population prevalence of asthma and atopy among asthmatic subjects and among the nonasthmatic part of the population. Results: No correlation was found between the prevalence of asthma (range 1.8–44.1%) and atopy (range 5.8–63.9%) in these 37 populations of children (r = 0.052, p = 0.761). Nevertheless, the prevalence of atopy among asthmatics strictly correlated with the prevalence of atopy in nonasthmatics (r = 0.900, p< 0.001, slope 1.364). Conclusion: The prevalence of asthma and atopy varies worldwide and at various time points and independently undergoes the influence of powerful environmental factors. The almost perfect correlation we found between atopy in asthmatics and atopy in the nonasthmatic part of the childhood population shows that the prevalence of atopy in asthma depends on environmental factors that simultaneously induce atopy in asthmatic and nonasthmatic subjects.

Background: Poor asthma control can lead to exercise-induced bronchoconstriction (EIB), but the relationship between subjective disease control and EIB is unclear. No studies have compared asthma control test (ACT) scores of children with those of their parents regarding EIB. We assessed whether ACT scores predict the occurrence of EIB in two age groups. We also evaluated ACT scores and objective measures as explanatory variables for airway response to exercise. Methods: Patients (71 aged <12 years, 93 aged ≥12 years) and their parents completed an ACT questionnaire separately. Current therapy, skin prick testing and spirometry at baseline and after exercise were assessed. EIB was defined as a fall in FEV1 of at least 12% from baseline. Sensitivity and specificity for cut-off values of ACT scores predictive of EIB were plotted, and the Area Under Curve (AUC) was described. Results: Atopy and current therapy were similarly frequent. EIB was observed in 23.9% of children aged <12 years and in 33.3% aged ≥12 years. EIB occurrence in subjects previously scored as having full control (25), partial control (20-24) and no control (<20) varied according to the age group and responder. Percentages of EIB cases increased as ACT scores decreased in children aged ≥12 years alone (child ACT scores, 25: 21.9%, 20-24: 31.1%, <20: 62.5%, p=0.017). Plots for ACT scores as predictors of EIB yielded low non-significant AUC values in children aged <12 years; by contrast, moderate AUC values emerged in children aged ≥12 years (child: 0.67, p=0.007; parent: 0.69, p=0.002). Sensitivity of ACT scores below 20 as a predictor of EIB was low in older children (child: 32.3%, parent: 22.6%), whereas specificity was high (child: 90.3%, parent: 93.5%). Multiple regression analysis with percent fall in FEV1 as dependent variable included FEV1/FVC%, ACT child score and gender in the prediction model ( r=0.42, p=0.000). Conclusion: ACT scores are a more effective means of excluding than confirming EIB in asthmatic patients aged ≥12 years; their predictive value decreases in younger patients. ACT scores together with lung function may help to predict airway response to exercise. New tools for pediatric asthma assessment may optimize this association.

Smoking is harmful for respiratory function. In young to middle-aged men the damage is insidious and difficult to demonstrate. The respiratory impairment could increase under specific stressful conditions in the professional environment. On the hypothesis that exhaled markers are useful for assessing airway susceptibility to inhaled irritants, we measured exhaled markers and lung function in smoking and non-smoking engine-driver military coastguards before and after a patrol at sea. Eighteen men, mean age 39 yrs (range 23–58 yrs), 8 smokers, underwent spirometry, exhaled and nasal nitric oxide (eNO, nNO), exhaled carbon monoxide (CO) and exhaled breath condensate (EBC) for measures of hydrogen peroxide (H₂O₂), leukotriene B4 (LTB4), proteins (Prots), 8-isoprostanes (8-IsoPs), nitrite (NO₂) and nitrosothiols (RS-NOs) at baseline and after an 8-hour patrol navigation on board small, high-speed diesel-powered ships. At baseline, the smokers showed higher middle flows and CO levels, lower eNO and nNO than non-smokers, but similar levels of EBC markers; geometric means (95% confidence interval), CO: 23.6 (14.5 to 38.3) vs. 3.5 (2.5 to 5.3) ppm; eNO: 7.9 (4.8 to 12.9) vs. 26.7 (15.7 to 45.5) ppb, p=0.000. After navigation, Prots, 8-IsoPs and RS-NOs (but not lung function variables or other markers) significantly increased only in smokers; baseline vs post-navigation RS-NOs: 0.27 (0.11 to 0.65) vs. 1.30 (0.58 to 2.89) μmol, p=0.012. The respiratory consequences of a stressing environment in engine-driver military coastguards who actively smoke are better assessed by measuring EBC markers than by eNO, nNO or lung function. By increasing airway inflammation from oxidative-stress, tobacco smoking appears to interact with other chemical or physical factors elicited during sea navigation. Precisely what these factors are deserves further investigation.