Asthma, allergy and atopy in South-east Asian immigrants in Australia

The rising of allergic respiratory diseases in a changing world: from climate change to migration

INTRODUCTION

The rising of allergic respiratory diseases (ARDs) suggests a decisive role of environmental factors, that have dramatically changed in the last decades.

AREAS COVERED

This review addresses various aspects of the external exposome acting on the development, progression, clinical presentation and severity of ARDs. Climate change, air pollution and biodiversity loss act directly and through their complex interactions on atopic risk: reacent foundings on these aspects are discussed herein. The review also focuses on migration studies, underling the possible role of migrant status as an experimental model to study environment effects on atopy onset and progression.

EXPERT OPINION

Future perspective on this topic include prevention and mitigation strategies in regard to pollution and climate change, improvement of environmental monitoring methods, implementation of public health policies, further advances in 'omics' research and knowledge, prospective and immunological research on migrant populations and new policies to face human mobility.

Effects of Migration on Allergic Diseases

Studies in migrant populations provide vital opportunities to investigate the role of environmental factors in the pathogenesis of allergic disorders. Differences in allergy prevalence have been observed between migrants and native-born subjects living in the same geographical location. Immigrants who migrate from less affluent countries with lower allergy prevalence tend to have a lower prevalence of allergic disorders compared to native-born residents of the more affluent host country. The patterns of allergic disease prevalence also differ between first- and second-generation migrants. The timing of migration in relation to birth, age at migration, and duration of residence in the host country also influence one's atopic risk. A complex interplay of multiple environmental, socioeconomic, and cultural factors is likely responsible for these observed differences. Further research into the roles of various risk factors in modulating differences in allergic disease prevalence between migrant and native populations will enhance our understanding of the complex gene-environment interactions involved in the pathogenesis of allergic disorders.

The Melbourne epidemic thunderstorm asthma event 2016: an investigation of environmental triggers, effect on health services, and patient risk factors

BACKGROUND

A multidisciplinary collaboration investigated the world's largest, most catastrophic epidemic thunderstorm asthma event that took place in Melbourne, Australia, on Nov 21, 2016, to inform mechanisms and preventive strategies.

METHODS

Meteorological and airborne pollen data, satellite-derived vegetation index, ambulance callouts, emergency department presentations, and data on hospital admissions for Nov 21, 2016, as well as leading up to and following the event were collected between Nov 21, 2016, and March 31, 2017, and analysed. We contacted patients who presented during the epidemic thunderstorm asthma event at eight metropolitan health services (each including up to three hospitals) via telephone questionnaire to determine patient characteristics, and investigated outcomes of intensive care unit (ICU) admissions.

FINDINGS

Grass pollen concentrations on Nov 21, 2016, were extremely high (>100 grains/m³). At 1800 AEDT, a gust front crossed Melbourne, plunging temperatures 10°C, raising humidity above 70%, and concentrating particulate matter. Within 30 h, there were 3365 (672%) excess respiratory-related presentations to emergency departments, and 476 (992%) excess asthma-related admissions to hospital, especially individuals of Indian or Sri Lankan birth (10% vs 1%, p<0·0001) and south-east Asian birth (8% vs 1%, p<0·0001) compared with previous 3 years. Questionnaire data from 1435 (64%) of 2248 emergency department presentations showed a mean age of 32·0 years (SD 18·6), 56% of whom were male. Only 28% had current doctor-diagnosed asthma. 39% of the presentations were of Asian or Indian ethnicity (25% of the Melbourne population were of this ethnicity according to the 2016 census, relative risk [RR] 1·93, 95% CI 1·74-2·15, p <0·0001). Of ten individuals who died, six were Asian or Indian (RR 4·54, 95% CI 1·28-16·09; p=0·01). 35 individuals were admitted to an intensive care unit, all had asthma, 12 took inhaled preventers, and five died.

INTERPRETATION

Convergent environmental factors triggered a thunderstorm asthma epidemic of unprecedented magnitude, tempo, and geographical range and severity on Nov 21, 2016, creating a new benchmark for emergency and health service escalation. Asian or Indian ethnicity and current doctor-diagnosed asthma portended life-threatening exacerbations such as those requiring admission to an ICU. Overall, the findings provide important public health lessons applicable to future event forecasting, health care response coordination, protection of at-risk populations, and medical management of epidemic thunderstorm asthma.

FUNDING

None.

Risk factors for eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic antigen driven disease, whereby food and/or aeroallergens result in inflammation and luminal narrowing, and the clinical symptoms of dysphagia and food bolus obstruction events (FBOE). Established risk factors are male gender, Caucasian race and atopy. Increased risk amongst family members, and a single nucleotide polymorphism (SNP) in a gene coding thymic stromal lymphopoietin (TSLP) on the pseudoautosomal region of the X and Y chromosomes supports a genetic predisposition. Environmental factors including the timing and nature of food and aeroallergen exposure to the developing immune system may be important, whilst esophageal barrier function integrity and the influence of microbiota are worthy of future research.

"United airways disease" and phenotypic peculiarities of respiratory allergy in immigrants

Allergy is the result of a complex interaction between genetic background and environmental factors, including exposure to allergens and lifestyle. Migration is a process that involves many radical changes in the environment, including diet, pollutants, allergens, different housing conditions, and patterns of infections. Thus, studies in immigrants may provide important information about the role of environmental factors in the development of allergic respiratory diseases. Several studies addressed this aspect and consistently found that migrants develop allergies at different rates from the local population, and very often the symptoms appear with a delay of 3 to 5 years after migration. More recent data showed that the severity of allergic diseases is greater in migrants, and that usually the onset is with associated asthma and rhinitis. The immigration model strongly suggests that environmental factors overcome the genetic background, and that the clinical phenotype of respiratory allergy in migrants has some peculiarities.

A temporal decline in asthma but not eczema prevalence from 2000 to 2005 at school entry in the Australian Capital Territory with further consideration of country of birth

BACKGROUND

Asthma prevalence has declined in some countries over the past 10 years. Most reports have been based on population surveys conducted at two points of time in a given location. Comparisons across countries and time periods can be limited by differences in study methodology or disease diagnostics in different communities. Here, we examined trends in asthma prevalence using serial annual data and further examine the importance of country of birth.

METHODS

The source population has children aged 4-6 commencing school in the Australian Capital Territory from 2000 to 2005 inclusive. Over 80% of these children and their families completed a health questionnaire on asthma, other atopic disease and respiratory symptoms using some questions from the International Study of Asthma and Allergies in Childhood (n = 22 882). Current asthma has been previously validated against physician assessment in this setting.

RESULTS

The prevalence of current asthma declined (P < 0.001) but eczema ever increased (P < 0.001) from 2000 to 2005. The asthma decline was predominantly linear in form, and accompanied by a reduction in night cough and shortness of breath but not recent wheeze. Compared with Australian-born children, children from New Zealand and the United Kingdom had a similar prevalence of asthma, hay fever and eczema history. However, children born in other countries, such as Asia, generally had a lower prevalence of these disorders. The temporal trends for atopic disorders or respiratory symptoms did not differ for overseas-born compared with Australian-born children.

CONCLUSION

The decline in current asthma prevalence from 2000 to 2005 was linear in form and appeared uncoupled from trends in child eczema. Country of birth was associated with marked variation in atopic disorder prevalence. The similar temporal trends for Australian vs overseas-born children indicate that the factors underlying the asthma prevalence decline are unlikely to be only in the pre-natal period.

Associations of physician-diagnosed asthma with country of residence in the first year of life and other immigration-related factors: Chicago asthma school study

BACKGROUND

Among Mexican Americans in the United States, US-born children have higher rates of asthma than their Mexico-born peers.

OBJECTIVE

To evaluate the associations of immigration-related variables with physician-diagnosed asthma in a sample of Mexican American children.

METHODS

We analyzed data from the ongoing Chicago Asthma School Study, a population-based cross-sectional study, for 10,106 Mexican American schoolchildren in Chicago, Illinois.

RESULTS

Mexican American children who lived in the United States in the first year of life were more likely to have physician-diagnosed asthma than their peers who lived in Mexico in the first year of life, independent of age, sex, income, language, and country of birth (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.09-2.94). The risk of asthma in US-born children was higher (but not significantly) than that observed in Mexico-born children after accounting for covariates, including country of residence in the first year of life (OR, 1.37; 95% CI, 0.86-2.18). Long-term immigrants (lived in the United States for 10 years) had an increased risk of asthma compared with short-term immigrants (lived in the United States for <10 years), independent of country of residence in the first year of life (OR, 1.93; 95% CI, 1.00-3.73).

CONCLUSION

These findings confirm the importance of early childhood exposures and environmental factors that are modified with migration and acculturation in asthma development.

Asthma in young south Asian women living in the United Kingdom: the importance of early life

BACKGROUND

Studies of immigrants suggest that the environment during fetal life and duration of residence in the host country might influence the development of asthma. Little is known about the importance of the timing of the exposure in the host country and whether migrants might be especially vulnerable in certain age windows.

OBJECTIVE

We compared the reported prevalence of asthma between young white and south Asian women in the United Kingdom, and investigated associations with country of birth and age at immigration.

METHODS

A questionnaire on atopic disorders was posted to 2380 south Asian and 5796 white young mothers randomly sampled in Leicestershire. Data on ethnicity were also available from maternity records. Data were analysed using multivariable logistic regression and a propensity score approach. Results The reported prevalence of asthma was 10.9% in south Asian and 21.8% in white women. South Asian women who migrated to the United Kingdom aged 5 years or older reported less asthma (6.5%) than those born in the United Kingdom or who migrated before age 5 (16.0%), with an adjusted odds ratio of 0.38 [95% Confidence Interval 0.23-0.64, P<0.001]. For those who migrated aged over 5 years, the prevalence did not alter with the duration of residence in the United Kingdom. Current exposure to common environmental risk factors had relatively little effect on prevalence estimates.

CONCLUSION

These data from a large population-based study support the hypothesis that early life environmental factors influence the risk of adult asthma.

Asthma, atopy, and lung function among racially diverse, poor inner-urban Minneapolis schoolchildren

As part of an assessment of schoolchildren's environmental exposures and health, a probability sample of 136 children from diverse racial/ethnic backgrounds was drawn from grades 2-5 of two inner-urban Minneapolis schools (Whittier, Lyndale). Questionnaires were administered to a parent/guardian; blood samples for IgE and lung function tests were obtained. Overall adjusted rates for lifetime asthma (15.4%; 95%CI 9.3-21.5%), asthma in the last 12 months (13.6%; 7.8-19.4%), and current asthma medication use (10.5%; 5.3-15.7%) were higher than reported US national rates. Adjusted rates for lifetime physician-diagnosed asthma differed significantly among racial/ethnic groups (P<0.01): African-Americans (25.9%), White/Others (25.8%), Hispanics (9.3%), Somalis (1.8%), Asians (0%). Corresponding rates for atopy (total IgE>100 IU/mL or an allergen-specific IgE>0.35 IU/mL) were: African-Americans (66.6%), White/Others (100%), Hispanics (77.2%), Somalis (78.1%), Asians (81.8%). Lung function (FEV1, FVC) was analyzed by linear regression using log-transformed data: significant race-specific differences in lung function were found relative to White/Others (P<0.001 for each racial/ethnic group): African-Americans (FEV1 -16.5%, FVC -16.9%), Somalis (-22.7%, -26.8%), Hispanics (-12.2%, -11.4%) and Asians (-11.1%, -12.4%). Females had significantly lower FEV1 (-8.8%) and FVC (-11.0%) than males. An unexplained, significant difference in children's lung function was found between the two schools. A history of physician-diagnosed asthma was not associated with decreased lung function. Factors other than poverty, inner-urban living, and IgE levels (atopy) need to be considered in the development of childhood asthma.

Atopy and asthma in migrants

Atopy and asthma result from the effects of environmental factors on genetically susceptible persons, and different prevalence rates have been documented worldwide. In developed and industrialized countries a higher prevalence of atopy and asthma is observed as compared with undeveloped and less affluent countries. Migration involves exposure to a new set of pollutants and allergens. In addition, it involves several socioeconomic and cultural issues such as housing conditions, diet and accessibility to medical services, all of which are likely to affect migrants' health. Migration studies provide information on the role of environmental factors in the development of atopy and asthma. Immigration to allergy-prevalent countries causes more allergies and asthma in immigrants as compared to the prevalence of atopy in their countries of origin. The increase in allergy and asthma is usually not related to ethnicity, but in certain populations may play an important role. Studies on migrants support the notion that lifestyle and environmental factors in western industrialized countries facilitate atopy and asthma. The effect is time-dependent. Acquiring allergy is influenced by the age at the time of immigration. Migrants, in general, are more prone to the development of allergies than the local population. Low hygiene prior to immigration does not seem to protect against the development of atopy or asthma. Vaccinations do not affect the development of atopy or asthma in the general population and in migrants. Migrants should be aware of the potential of developing allergies and/or asthma. Strategies for primary prevention in high-risk atopic individuals and secondary prevention guidelines should be developed both for populations in developing countries as well as for immigrants from such countries to atopy-prevalent developed countries.

The increase in allergic respiratory diseases: survival of the fittest?

The prevalence of allergic respiratory diseases, asthma and allergic rhinoconjunctivitis, has increased since the advent of industrialization. The inverse relationship between the number of infections early in life and atopy has been interpreted as the "hygiene hypothesis." That is, many infections early in life promote the development of T helper type 1 cytokines, while fewer infections early in life favor the development of T helper type 2 (Th2) cytokines and atopy. An alternate interpretation of the same data, that atopy is protective against infections early in life, is rarely considered. With epidemiologic, historical, and immunologic data, I suggest that human evolution has favored individuals with an atopic predisposition. Th2 immune responses promote parity, and ensure successful pregnancy and term birth; provide the infant protection against infections and the inflammation induced by common pathogens in the first years of life until the immune system matures; and protect young adults exposed to viral respiratory pathogens. These traits are of particular value with the advent of industrialization, especially so in the era prior to the development of antibiotics. This theory contradicts the assumption that there is no biological or evolutionary advantage for allergic disease to exist in humans and has significant implications for our current and future treatments of allergic diseases.

Hypothesis: decreased use of pediatric aspirin has contributed to the increasing prevalence of childhood asthma

BACKGROUND

The prevalence of asthma, atopic eczema, and allergic rhinitis has increased over the last three decades in Western countries. Speculation on the causes of this trend have focused on changes in environmental factors. We hypothesize that the decreased use of aspirin in favor of acetaminophen, due to the association of aspirin with Reye's syndrome during febrile respiratory infections, may be contributing to these trends in the United States.

DATA SOURCES

A detailed literature search was conducted utilizing Medline. Studies considered relevant and important involving both humans and animals in English language were used.

HYPOTHESIS

In the United States, the documented prevalence of childhood asthma has increased since 1970, but the rate of this increase accelerated upward beginning in the early 1980s when the use of pediatric aspirin decreased. During the resolution of common respiratory viral infections, prostaglandin E2 (PGE2) is produced through the actions of cyclooxygenase-2 (COX-2). Aspirin, but not acetaminophen, inhibits COX-2 activity. As PGE2 promotes TH2 and inhibits THI type cytokine generation, we hypothesize that the decreased use of aspirin may be a factor in facilitating allergic sensitization and asthma by augmenting the relative TH1/TH2 cytokine imbalance in genetically predisposed children.

CONCLUSION

We have presented an hypothesis based upon epidemiologic trends, known biologic effects of cytokines and PGE2 on allergic sensitization, and a potentially relevant pharmacologic effect of aspirin to explain a component of the increasing prevalence of childhood asthma in the United States. We suggest this theory be examined further in animal models as well as in other countries where the prevalence of childhood asthma is increasing.

The problem of atopic eczema: aetiological clues from the environment and lifestyles

Atopic eczema is the most common inflammatory skin disease in children, affecting around 10% of children in the developed world. It can be a distressing condition, influencing children's well-being, personal and educational development, and family life, and it has huge economic implications for health services and individual budgets. Like other atopic diseases such as asthma and hay fever, the prevalence of atopic eczema has increased substantially over the last 30 years, for reasons largely unknown. Although a genetic predisposition to the disease has been implicated, evidence from a range of sources suggests that environmental factors play a crucial role in the disease expression. This paper reviews the epidemiology of atopic eczema, with particular attention to potential environmental aetiological factors and draws evidence from studies in the UK and internationally. First, atopic eczema has been found to vary socially and to be more prevalent in the UK among social class I and II families than among other socio-economic groups. Second, it has been suggested that cross infection from other siblings in large families may have a protective role in atopic disease expression. Third, it has been proposed that an increased risk of atopic eczema may result from decreases in helminthic infestation. Fourth, studies of migrant groups have shown large increases in disease prevalence compared with migrants' country of origin, suggesting clues as to the importance of socio-economic and environmental changes such as those associated with industrialization. Finally, a distinct and consistent geographical pattern of eczema has been observed in the UK which cannot be explained by social class distribution. The various types of study have attempted to identify reasons for differences in prevalence but, to date, no definitive causation has been identified. In some cases, specific risk factors have been suggested and include house dust mites, dietary allergens and irritants. It is argued here that the aetiology is unlikely to be simple or uni-causal and that an understanding of the relationships between the disease and behaviour, lifestyle, home and external environmental factors is crucial. This paper reports the preliminary stages of an interdisciplinary research project involving dermatologists, epidemiologists and health geographers, and calls for investigation into associations between atopic eczema and possible environmental and lifestyle factors. These include behavioural factors, microenvironment factors and macroenvironments.