Regional variation of airway hyperresponsiveness in children with asthma

Prevalence of asthma in a large group of Israeli adolescents: influence of country of birth and age at migration

BACKGROUND

The occurrence of asthma has geographic variations and is lower in developing compared with industrialized countries. Both environmental and genetic factors may influence its prevalence. We aimed to evaluate the importance and effect of immigration (country of birth and age at immigration to Israel) on the prevalence of asthma in a large group of Israeli adolescents.

METHODS

Computerized medical records of 17-year-old adolescents, who underwent routine examination before military recruitment, were studied. The sample comprised both native-born Israelis (NBI) and immigrants from Ethiopia, the Former Soviet Union (FSU), and Western countries (WC). Asthma was defined as clinical symptoms and signs compatible with the disease accompanied by abnormal spirometry or documented chronic use of inhaled steroids.

RESULTS

Our cohort consisted of 1 466 654 adolescents, including 1 317 556 (89.8%) NBI and 149 098 (10.2%) immigrants. The prevalence of asthma at age 17 was higher in NBI compared with Ethiopian immigrants [4.7% (61 921) vs 2.6% (418), respectively, P < 0.0005], lower compared with immigrants from WC [5.6% (2177), P < 0.0005], and similar to immigrants from the FSU. Further analysis of the association between age at immigration and the risk for developing asthma showed that the younger immigrants from the FSU and Ethiopia arrived to Israel, the higher their prevalence of asthma at the age of 17 was.

CONCLUSIONS

Both environmental and genetic factors seem to influence the prevalence of asthma in 17-year-old adolescents. However, the higher risk for developing asthma associated with young age of immigration points toward an environmental predominance.

Major gene effect and additive familial pattern of inheritance of asthma exist among families of probands with sickle cell anemia and asthma

In the United States, sickle cell anemia (SCA) affects approximately 1 in 400 African-American newborns. Acute episodes of pain and acute chest syndrome (ACS) are the two leading causes of hospitalization. A relationship between the diagnosis of asthma and the incidence of pain and ACS has been established. We tested the hypothesis that a familial pattern of inheritance of asthma exists among first degree relatives of probands with SCA and asthma. Segregation analysis was performed in 104 families ascertained through affected probands. Of these, 19.7% (41/208) of the parents and 31.8% (28/88) of siblings of affected probands reported having been told by a doctor he or she had asthma at any age. Modes of inheritance were tested, using the Pedigree Analysis Package parameterized for the discrete trait of asthma affection status. A major effect was present and significant. Further tests were performed to determine whether transmission probabilities of the major effect followed Mendelian expectations. The additive mode of inheritance was the most parsimonious, while the residual heritability was found negligible. Our results support the hypothesis that a familial pattern of inheritance of asthma exists among first degree relatives of probands with SCA and asthma, suggesting that asthma is a co-morbid condition with SCA rather than a lung disease phenotype mimicking asthma.

Asthma severity and atopy: how clear is the relationship?

BACKGROUND

The relationship between asthma severity and atopy is complex. Many studies have failed to show significant relationships between clinical severity or lung function and markers of atopic sensitisation.

AIM

To determine whether increasing asthma severity is related to atopic sensitisation in a population of children with asthma.

METHODS

A total of 400 children (7-18 years) with asthma were recruited as part of a multicentre study of the genetics of asthma. Detailed phenotypic data were collected on all participants. Associations between measures of asthma severity and atopic sensitisation were sought using multilevel models allowing variation at the individual and family level.

RESULTS

Children recruited to the study had a range of asthma severities, with just over a third having mild persistent asthma. The logarithm of total serum IgE was associated with increased asthma severity score, decreased FEV1, increased airways obstruction, risk of hospital admission, and inhaled steroid use. Increasing skin prick test reactivity to a panel of seven aeroallergens was associated with increased risk of hospital admission, use of an inhaled steroid, and airways obstruction. The results remained highly significant after corrections for age, gender, and birth order.

CONCLUSIONS

In children with asthma, increasing atopy is associated with increasing asthma severity. However, the relationships between asthma severity and skin prick tests, and asthma severity and total serum IgE values, appear subtly different.

Effects of glutathione S-transferase M1, T1 and P1 on lung function in asthmatic families

RATIONALE

Previous data have suggested that glutathione-S-transferase (GST) genotypes are important in determining the rate of lung function growth in childhood. This effect was most marked in Caucasian children with asthma.

OBJECTIVES

We investigated the association of lung function with GSTM1, GSTP1 and GSTT1 genotypes in Caucasian families with asthma.

METHODS

Four hundred and eighteen children and 316 parents from 224 Caucasian families were recruited via a child with asthma, the proband. Associations between lung function and GST genotype were determined using multilevel models.

RESULTS

There were no observed associations between lung function and GST genotype in parents. However, in the children, the GSTP1 val(105)/val(105) and GSTM1 null genotypes were associated with significantly higher forced expiratory volume in 1 s (FEV(1)) and FVC values as percentage of predicted. This effect was not statistically significant in the probands but was marked in their siblings in whom GSTP1 val(105)/val(105) was associated with 9.4% higher FEV(1) and 10.7% higher FVC (P=0.005 and 0.001, respectively). The GSTM1 null genotype was associated with a 6.7% higher FEV(1) and 4.1% higher FVC (P=0.003 and 0.063, respectively). These effects remained significant after correcting for the confounders of individual atopic status, tobacco smoke exposure and familial aggregation of lung function values.

CONCLUSIONS

GSTM1 and GSTP1 genotypes are important determinants of lung function in childhood. The smaller differences seen in probands are predicted by a simple model in which more rapid decline in lung function is seen in these individuals.

Clinical and technical factors affecting pH and other biomarkers in exhaled breath condensate

Exhaled breath condensate (EBC) pH appears to be a robust measure of asthma. However, the association between EBC pH and clinical factors and airway inflammatory markers remains unclear. The objectives of this study were to investigate the factors determining EBC pH in asthmatic children, and the reproducibility and effects of collection devices on EBC pH in nine healthy, nonsmoking adults. EBC was collected once from asthmatic children using EcoScreen, and from adults over 3 consecutive days using both RTubes and EcoScreen. EBC pH was measured immediately in non-deaerated samples by microelectrode pH meter. Concentrations of 8-isoprostane, cysteinyl leukotrienes (cys-LT), and leukotriene B4 (LTB4) were measured using enzyme immunoassay. Exhaled nitric oxide concentration (FeNO) was measured by chemiluminescence. Fifty-eight asthmatics (16 intermittent, 12 mild persistent, and 30 moderate-to-severe persistent) were recruited. EBC pH was lower among patients with moderate-to-severe persistent than intermittent asthma (P = 0.046). This marker correlated inversely with disease severity score (rho = -0.276, P = 0.036), but not FeNO or other EBC biomarkers. Bland-Altman analyses found pH but not other EBC biomarkers to be reproducible, which were confirmed by its low coefficient of variation (2.7%; range, 0.4-5.2%). There was poor correlation between pH in EBC collected by RTube and EcoScreen (rho = 0.059, P = 0.784). Factor analysis selected four factors that explained 67.5% of the total variance, and EBC pH clustered with both cys-LT and LTB4. In conclusion, our results suggest that pH in non-deaerated EBC is influenced by asthma severity in children. EBC pH measurement is reproducible, but is dependent on the collection devices used.