Environmental influences on asthma and allergy

Relationship between exposure to ozone and exacerbation requiring hospital admission among patients with asthma: a case-control study in central Taiwan

OBJECTIVE

The convergence of asthma and air pollutants in ageing populations is currently a growing health issue worldwide, and hence there is an essential need to investigate the association between exposure to air pollution, particularly ozone (O₃), and exacerbation requiring admission in patients with asthma.

SETTING

A case-control study at a tertiary referral hospital in central Taiwan.

PARTICIPANTS

We used an asthma cohort, which included 11 400 patients with asthma, for the period 2006-2018 at Taichung Veterans General Hospital.

PRIMARY AND SECONDARY OUTCOME MEASURES

We identified patients who had admitted for exacerbation as cases and selected patients with asthma without exacerbation, matching (1:4) the cases for age, gender and season of exacerbation, as controls. Data on hourly level of air pollutants were obtained from the Taiwan Environmental Protection Administration. We used conditional logistic regression and calculated adjusted ORs (adjORs) with 95% CIs.

RESULTS

We enrolled 11 400 participants with asthma, and 4.4% (501) of them had been admitted for exacerbation. Participants with asthma with exacerbation requiring hospitalisation were exposed to a higher level of O₃ 8-hour daily maximum (adjOR 1.009, 95% CI 1.001 to 1.016) and were more likely to have high Charlson Comorbidity Index (CCI ≥3; adjOR 2.198, 95% CI 1.729 to 2.794) and asthma-chronic obstructive pulmonary disease overlap (adjOR 4.542, 95% CI 3.376 to 6.611) compared with those without exacerbation. The aforementioned associations between exacerbation of asthma requiring hospitalisation and exposure to O₃ were similar when defined by either O₃ 1-hour daily maximum or O₃ 24-hour average. Moreover, the O₃ relevant exacerbation of asthma mainly existed in those aged older than 65 years and patients with medical comorbidities, including gastrointestinal diseases, cardiovascular diseases, neurological diseases, diabetes and renal disease.

CONCLUSIONS

Our findings highlight the need for vigilance of exposure to O₃ among elderly with asthma, particularly those with medical comorbidities. Further studies are warranted to investigate the underlying mechanisms.

Spatiotemporal Variations in Ambient Ultrafine Particles and the Incidence of Childhood Asthma

Rationale: Little is known regarding the impact of ambient ultrafine particles (UFPs; <0.1 μm) on childhood asthma development. Objectives: To examine the association between prenatal and early postnatal life exposure to UFPs and development of childhood asthma. Methods: A total of 160,641 singleton live births occurring in the City of Toronto, Canada between April 1, 2006, and March 31, 2012, were identified from a birth registry. Associations between exposure to ambient air pollutants and childhood asthma incidence (up to age 6) were estimated using random effects Cox proportional hazards models, adjusting for personal- and neighborhood-level covariates. We investigated both single-pollutant and multipollutant models accounting for coexposures to particulate matter ≤2.5 μm in aerodynamic diameter (PM_2.5) and NO₂. Measurements and Main Results: We identified 27,062 children with incident asthma diagnosis during the follow-up. In adjusted models, second-trimester exposure to UFPs (hazard ratio per interquartile range increase, 1.09; 95% confidence interval, 1.06-1.12) was associated with asthma incidence. In models additionally adjusted for PM_2.5 and nitrogen dioxide, UFPs exposure during the second trimester of pregnancy remained positively associated with childhood asthma incidence (hazard ratio per interquartile range increase, 1.05; 95% confidence interval, 1.01-1.09). Conclusions: This is the first study to evaluate the association between perinatal exposure to UFPs and the incidence of childhood asthma. Exposure to UFPs during a critical period of lung development was linked to the onset of asthma in children, independent of PM_2.5 and NO₂.

Effect modification of perinatal exposure to air pollution and childhood asthma incidence

Perinatal exposure to ambient air pollution has been associated with childhood asthma incidence, however, less is known regarding the potential effect modifiers in this association. We examined whether maternal and infant characteristics modified the association between perinatal exposure to air pollution and development of childhood asthma.761 172 births occurring between 2006 and 2012 were identified in the province of Ontario, Canada. Associations between exposure to ambient air pollutants and childhood asthma incidence (up to age 6) were estimated using Cox regression models.110,981 children with asthma were identified. In models adjusted for postnatal exposures, second trimester exposures to particulate matter with a diameter ≤2.5 μm (PM2.5) (Hazard Ratio (HR) per interquartile (IQR) increase=1.07, 95% CI: 1.06-1.09) and nitrogen dioxide (NO2) (HR per IQR increase=1.06, 95% CI: 1.03-1.08) were associated with childhood asthma development. Enhanced impacts were found among children born to mothers with asthma, those who smoked during pregnancy, boys, those born preterm, of low birth weight and among those born to mothers living in urban areas during pregnancy.Prenatal exposure to air pollution may have a differential impact on the risk of asthma development according to maternal and infant characteristics.

Geographical and sociodemographic risk factors for allergic diseases in korean children

PURPOSE

(a) To examine geographical distribution of childhood allergic diseases in Korea and (b) to identify geographical and sociodemographic risk factors for allergic diseases.

METHODS

Data on doctor-diagnosed asthma during lifetime and allergic rhinitis and atopic dermatitis during the past 12 months of 8,631 children (≤ 18 years) were obtained from the Third Korea National Health and Nutrition Examination Survey, along with information on housing type and presence of an indoor smoker. The SaTScan program identified geographical case clusters of allergic diseases, and multiple logistic regression determined risk factors, including geographical case clusters, for each allergic disease.

RESULTS

Prevalence of asthma, allergic rhinitis, and atopic dermatitis was 3.2%, 13.2%, and 15.5%, respectively. Older children (10-18 years) were more likely to have allergic rhinitis whereas younger children were more likely to have atopic dermatitis. It is noteworthy that children living in areas of geographical risk for asthma and atopic dermatitis were more likely to develop the respective allergic disease than children living in other areas (odds ratio [OR] = 3.47 for asthma, and OR = 9.74 for atopic dermatitis).

CONCLUSIONS

This study indicates that the areas in which children live may influence the development of certain allergic diseases. Implications include the need to assess geographical location of children with allergic diseases and to develop community-based preventive programs for children with allergic diseases.

Early Interventions in Allergic Diseases

Atopy has been defined as the genetic predisposition to develop IgE antibody responses to a variety of common environmental allergens. Clinically, atopy is expressed by asthma, allergic rhinoconjunctivitis and atopic dermatitis. It has been recognized that the “atopic march” evolves from food allergy and atopic dermatitis in the first 2 years of life, followed by asthma and allergic rhinitis. Over the past 30 years, the prevalence of allergies and asthma has increased significantly in developed countries, and asthma is one of the most common chronic diseases in children. Evidence indicates that environmental factors acting early in life, including respiratory viral infections, exposure to pets and microbial products, day-care attendance, breast feeding, and exposure to allergens, tobacco smoke and other pollutants, are key events for establishment of sensitization and development of chronic, persistent symptoms of allergic diseases [1]. It is thought that gene—environment interactions play a crucial role in these processes. Therefore, attempts to successfully prevent development of allergic diseases should be a priority.

At present, there are no genetic markers for atopy or asthma which could be used routinely in clinical practice and family history of atopy has been used to identify children genetically at-risk of developing allergic diseases. These children from high-risk families have been the focus of most of the intervention studies.

Why modest geographic effects for asthma? Pharmaceutical treatment as neutralizing mechanism

Research on geographic health effects has been greatly advanced with the development of multilevel statistical techniques but less is known about the possible mechanisms by which social and geographical environments may affect physical health. In spite of well-established relationships between asthma etiology and the broader living environments, multilevel research on asthma shows at best marginal geographic effects. Based on in-depth, open-ended interviews with 50 caretakers of school-age children (6-12 years) diagnosed with asthma living in two different communities, this article elucidates mechanisms by which neighborhood effects may be neutralized. Caretakers of children with mild, controllable asthma attempt to create asthma-safe zones by administering long-term control and quick-relief medication, by removing indoor environmental triggers and by avoiding dangerous environments. At home, school and outdoors, the key strategy to control asthma was the use of relatively effective and accessible medications. Children with severe asthma did not benefit as much from medications but it was unclear that different communities made a difference in asthma care.

The changing prevalence of asthma, allergic rhinitis and atopic eczema in African adolescents from 1995 to 2002

The prevalence of asthma and allergic disease in children has been increasing in developed countries, but there is little information on these trends in Africa. The aim of this study was to assess time trends in the symptoms of asthma, allergic rhinitis, and atopic eczema among South African adolescents. The study was carried out by comparing cross-sectional data from two International Study of Asthma and Allergies in Childhood (ISAAC phase I and phase III) questionnaire based surveys conducted 7 yr apart of self-reported symptoms in 13- to 14-yr-old adolescents. In both surveys, schools in the same geographical area in Cape Town, South Africa, were randomly selected. A school-based sample of 5178 (in 1995) and 5037 (in 2002) pupils participated. The 12-month prevalence of wheezing (16% vs. 20.3%), exercise-induced wheeze (21.5% vs. 32.5%), nocturnal cough (23.6% vs. 36.6%), sleep disturbance due to wheeze (9.6% vs. 16%), or severe wheeze (5.1% vs. 7.8%) increased significantly, as measured by the written questionnaire. A rise in asthma symptoms was confirmed by the video questionnaire responses, in which the 12-month prevalence of wheezing (6.5% vs.11.2%), exercise-induced wheeze (11.5% vs. 13.9%), nocturnal wheeze (3.9% vs. 5.3%), nocturnal cough (11.6% vs. 19.2%), or severe wheeze (5% vs. 7%) also increased significantly. There was a small increase in the percentage of children diagnosed with asthma from 1995 to 2002 (13.1% vs. 14.4%), this was not significant. The 12-month prevalence of symptoms of allergic rhinitis (30.4% vs. 38.5%), rhinoconjunctivitis (17.6% vs. 24.3%) and eczema (11.8% vs. 19.4%) also increased significantly. An increase in the prevalence of allergic symptoms occurred in girls and boys. Limitation of daily activity from nasal symptoms (22.3% vs. 37.8%) and sleep disturbance because of eczema (8.4% vs. 15.7%) increasingly affected quality of life on the quality of life. Symptoms of asthma, allergic rhinitis and atopic eczema in adolescents have increased over the past 7 yr in this geographical area. Allergic diseases are common in this group of adolescents and increasingly impair their quality of life.