Martín Becerril-Ángeles

Passive Smoking Induces Leukotriene Production in Children: Influence of Asthma

Background. Passive smoking is associated with poor asthma control in children, but the mechanism is unknown. Leukotrienes are involved in the asthma pathogenesis and their synthesis is increased in adult subjects who actively smoke. Objective. To evaluate whether passive smoking, as assessed by urinary cotinine levels, increases leukotriene production in children with or without asthma. Methods. This was a prospective, cross-sectional study in which children with stable intermittent asthma (without exacerbation) and healthy control children were studied through spirometry and urinary concentrations of cotinine and leukotriene E4 (LTE4). Both groups were balanced to include children with and without passive smoking. Results. Ninety children (49 with asthma and 41 controls, 54.4% females) aged 9 years (range, 5–13 years) were studied. Urinary LTE4 concentrations were progressively higher as cotinine levels increased (rS = 0.23, p = .03). LTE4 also correlated with body mass index (BMI) (rS = 0.30, p = .004), and multiple regression analysis revealed that BMI was even more influential than cotinine for determining LTE4 levels. LTE4 concentrations were unrelated with gender, age, or spirometry. In turn, cotinine inversely correlated with forced expiratory volume in one second (FEV1) (rS = −0.22, p = .04) and forced vital capacity (FVC) (rS = −0.25, p = .02), but when analyzed by groups, these relationships were statistically significant only in children with asthma. Conclusions. Exposure to environmental tobacco smoke, as assessed by urinary cotinine levels, was associated with an increased urinary concentration of LTE4, although BMI exerted more influence in determining its concentration. Urinary cotinine was associated with decreased lung function, mainly in children with asthma.

Altitude above 1500 m is a major determinant of asthma incidence. An ecological study

BACKGROUND Previous studies suggest an inverse correlation between asthma and altitude. In the present work, we performed an in-depth analysis of asthma incidence in the 758 Mexican counties covered by the largest medical institution in the country (∼37.5 million insured subjects), and evaluated its relationships with altitude and other factors. METHODS Asthma incidence in each county was calculated from new cases diagnosed by family physicians. Other variables in the same counties, including selected diseases, geographical variables, and socioeconomic factors, were also obtained and their association with asthma was evaluated through bivariate and multivariate analyses. RESULTS Median asthma incidence was 296.2 × 100,000 insured subjects, but tended to be higher in those counties located on or near the coast. When asthma incidence was plotted against altitude, a two-stage pattern was evident: asthma rates were relatively stable in counties located below an altitude of ∼1500 m, while these rates progressively decreased as altitude increased beyond this level (rS = -0.51, p < .001). Multivariate analysis showed that, once each variable was adjusted by the potential influence of the others, asthma incidence was inversely correlated with altitude (standardized β coefficient, -0.577), helminthiasis (-0.173), pulmonary tuberculosis (-0.130), and latitude (-0.126), and was positively correlated with acute respiratory tract infection (0.382), pneumonia (0.289), type 2 diabetes (0.138), population (0.108), and pharyngotonsillitis (0.088), all with a p ≤ .001. CONCLUSION Our study showed that altitude higher than ∼1500 m comprises a major factor in determining asthma incidence, with the risk of new-onset asthma decreasing as altitude increases. Other less influential conditions were also identified.