Copyright ©ERS Journals Ltd 2001 Symptoms of asthma, bronchial responsiveness and atopy in immigrants and emigrants in Europe1 Respiratory and Environmental Health Research Unit, IMIM, Barcelona, Spain, 2 Dept of Clinical Epidemiology and Public Health, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain, 3 Worldwide Epidemiology, GlaxoSmithKline R and D, Greenford, Middlesex, UK, 4 Dept of Public Health Sciences, Guy's, King's and St. Thomas' School of Medicine, Guy's Hospital, London, UK and 5 Dept of Experimental and Health Sciences, Universitat Pompeu Fabra (UPF), Barcelona, Spain CORRESPONDENCE: P. Burney, Dept of Public Health Sciences, Kings College, 5th floor Capital House, 42 Weston Street, London, SE1 3QD, UK. Fax: 44 20784 6605 Keywords: asthma, atopy, bronchial responsiveness, European Community Respiratory Health Survey, healthcare, migration
Received: March 20, 2000
Migration studies on asthma may provide information on its environmental causes. The European Community Respiratory Health Survey has potential advantages due to the number of countries involved, standardized collection of information, assessment of directionality of migration, and availability of physiological data on bronchial responsiveness and atopy. Prevalence rates of symptoms associated with asthma were compared for immigrants, emigrants and nonmigrants living in centres mostly in western Europe. Similar analyses were carried out for bronchial responsiveness (provocative concentration causing a 20% fall in forced expiratory volume in one second and slope) and atopy. Medication and use of health services were also explored. Overall, 1,678 (8.6%) of 19,516 participants were immigrants in the 18 countries participating in the study, of whom 581 were emigrants from one of the participating countries. Rates of asthma symptoms were higher in immigrants (odds ratio (OR): 1.21, 95% confidence interval (CI): 1.001.51) and emigrants (OR: 1.31, 95% CI: 0.961.51) compared to nonmigrants after controlling for area, sex, age and smoking status. However, bronchial responsiveness and atopy were equally distributed between immigrants, emigrants and nonmigrants. Use of health services was observed to be similar in migrants and nonmigrants with asthma. In the European Community Respiratory Health Survey, migrants reported more asthma symptoms, but had similar bronchial responsiveness, atopy, and use of health services when compared with the nonmigrant population. Migrants may have a greater susceptibility to asthma 1. Variations in the prevalence of disease and increased rates associated with time, migration and changing lifestyle highlight the importance of environmental agents in the induction of the disease 2. Compared with studies of cancer and cardiovascular disease, international migrant studies of asthma are scarce and very localized, tending to compare immigrants only with the host populations. Immigrants may suffer from psychological changes including somatization due to post-traumatic stress disorder and other anxiety disorders 3. As with the unemployed 4, migrants might lack access to medical care, as well as being more susceptible to respiratory and other conditions. The European Community Respiratory Health Survey (ECRHS) has previously provided information on the distribution of asthma and asthma-related phenotypes in the 2044-yr-old population within Europe and elsewhere 57. To study the effects of migration on asthma, the ECRHS has potential advantages: data from 14 European and four other countries, standardized information including direction of migration, and physiological data on atopy and bronchial responsiveness. By means of a cross-sectional analysis of the ECRHS, the authors have compared prevalence rates of asthma symptoms, bronchial responsiveness, atopy and use of health services by those with asthma in first-generation immigrants and emigrants, and nonmigrants.
Study design and sample The study design, methodology and objectives of the ECRHS have been described elsewhere 5. Briefly, the ECRHS was conducted in 38 areas of 18 countries from 19911993. A random sample of 3,000 males and females aged 2044 yrs from each of the participating areas was contacted and requested to complete a short screening questionnaire on respiratory symptoms. Subsequently, a 20% random sample (n=19,516) of the source population was asked to complete a long questionnaire, provide blood samples, undergo skin and forced spirometric tests, and have bronchial responsiveness measured through a methacholine challenge test 7.
Migration and social data Countries were stratified into zones according to whether they had a high, medium or low prevalence of asthma among nonmigrants. The groups were as follows: high: Australia, France, New Zealand, UK, USA; Medium: Denmark, Ireland, Italy, Sweden, Switzerland; low: Belgium, Germany, Iceland, Netherlands, Norway, Spain. India and Estonia had virtually no migrants and were excluded from these analyses.
Symptoms questionnaire, respiratory function and immunological measurements Bronchial responsiveness was defined as a provocative concentration causing a 20% fall in forced expiratory volume in one second (FEV1) (PD20) from the largest postdiluent volume during methacholine challenge with an estimated cumulative dose of 5.1 µmol methacholine 7. Because many participants will have censored data on bronchial responsiveness as measured by PD20, analysis was also carried out by calculating the slope, or regression coefficient of percentage decline in FEV1 with log dose 7. Atopy was assessed by means of serum-specific immunoglobulin-E (IgE) 6. A participant was considered as having a measurable specific serum IgE when he/she had a specific IgE >0.35 kU·L1 by the Pharmacia CAP method (Pharmacia Diagnostics, Uppsala, Sweden) to any of the following allergens: Dermatophagoides pteronyssinus, timothy grass, cat, Cladosporium, or a local allergen. The local allergen was birch for northern Europe, Parietaria for southern Europe and ragweed for the USA, New Zealand and Australia.
Medication and use of health services
Statistical analysis
Migration rates There were 1,678 immigrants in the present study, constituting 8.6% of the ECRHS study population. Overall, 581 (3.0%) were born in one of the participating countries, therefore being considered emigrants from these countries.
Migration rates varied widely between countries, the centres of the USA (27.9%), Switzerland (22.4%) and Australia (20.5%) had the highest rates of immigrants observed, while those of Italy (1.3%), Spain (2.0%) and Iceland (2.1%) had the lowest. India and Estonia had practically no immigrants, and therefore were excluded in the analyses. There were statistically significant differences in the rates of migration by age groups (p<0.01), the oldest group (4045 yrs) having the highest rate of migration (10.7%) and social class, with a higher percentage of manual class workers among immigrants than nonmigrants. There were no statistically significant differences in the rates of migration by sex or smoking status (table 1
Symptoms in migrants Higher prevalence rates of asthma symptoms were reported by immigrants (11.2%) and emigrants (11.0%) than nonmigrants (8.6%), both differences being statistically significant (p<0.01). The corresponding ORs adjusted by sex, age, and smoking were 1.21 (95% CI: 1.001.51) in immigrants and 1.31 (95% CI: 0.961.78) in emigrants compared to nonmigrants (table 2
Country of birth and country of residence In table 3
Bronchial responsiveness and atopy Similar prevalence rates of bronchial responsiveness (14.2% for immigrants, 15.0% for emigrants and 14.4% for nonmigrants) and atopy (40.6% for immigrants, 37.6% for emigrants and 38.8% for nonmigrants) were observed. Overall, migration did not modify the risk of either bronchial responsiveness or atopy (table 4
Use of health services Finally, the association between migration and use of medication in the last year, and use of health services, was explored in the individuals who reported symptoms associated with asthma (table 5
In this general population study of adults aged 2045 yrs in Europe, USA, Australia and New Zealand, migrants (both immigrants and emigrants) had a slightly higher prevalence of symptoms associated with asthma than those subjects defined as nonmigrants. The higher prevalence rates in immigrants could not be attributed to other variables such as sex, smoking or social class. There was a wide variation in the use of medication and health services in the previous year, as previously reported in subjects with asthma-related symptoms 13, 14. However, symptomatic individuals were treated and used health services evenly, irrespective of migration status. When country of birth and current country of residence were considered together, there was a lower prevalence of asthma in migrants in those areas of medium prevalence than in those areas of high prevalence, however, there was no clear pattern overall. Although this is compatible with the observations of Strachan et al. 15 and Leung et al. 16 that subjects who migrate tend to adopt the prevalence of the area to which they migrate, the fact that no pattern was observed on the rates of migration to/from countries where the asthma burden is very high (i.e. English speaking countries) or to/from countries where the asthma burden is lower, and that migration was not associated with higher rates of bronchial responsiveness or atopy, leads the authors to consider the present study as less conclusive. A number of limitations must be considered, namely nonresponse, sampling, the low number of immigrants and the lack of extended questionnaire data. There was a substantial nonresponse rate in the ECRHS, and despite intense efforts, the participation rate was about 60% for the long questionnaire and 4050% for respiratory and blood tests. However, this lack of response has not necessarily affected the validity of the results. It is unlikely that immigrants were selectively persuaded to participate in the study. Finally, because sampling strategy in each country was from official sources, only legal immigrants may have been included, although there is universal coverage of health benefits in most European countries for legal and illegal immigrants. One major limiting factor was the low number of immigrants reported in most of the participating countries, leading to a lack of power in analyses particularly when adjusting by confounding variables. There were limited data on migration in the questionnaire, and more specific analyses regarding to when asthma symptoms developed in relation to migration could not be performed.
A potential bias may come from language problems among immigrants, who might systematically report higher morbidity due to respiratory symptoms, similar to observations in some psychiatric surveys 17. Indeed, misclassification of asthma for shortness of breath via anxiety and hyperventilation cannot be ruled out in any migration study of asthma. Within the present study, a report of shortness of breath was more frequent in migrants than nonmigrants both in a crude analysis (OR: 1.35, 95% CI: 1.101.65) and in an analysis adjusted by country of residence, sex, age and smoking status (OR: 1.32, 95% CI: 1.071.64) (data not shown). However, adjusted risks were not significantly increased in migrants for reported attack of asthma (OR: 1.09, 95% CI: 0.851.42) and for currently taking medicines for asthma (OR: 1.08, 95% CI: 0.811.44). The increased report of asthma in migrants is, therefore, unlikely to be due to a labelling or diagnostic bias. Language difficulties could lead to migrants having poor asthma education, and therefore poor compliance 18 and more symptoms. However, there is no evidence that the migrants in this study had less access to services (table 4
A small number of published papers have assessed not only questionnaire data, but also other "harder" outcomes as in this study. Positivity to birch allergen by prick test and/or radioallergosorbent test in a survey performed in immigrants living in Sweden, was 16% in the persons who had been there To conclude, despite migrants reporting more symptoms associated with asthma than nonmigrants in the European Community Respiratory Health Survey, this study has to be considered as inconclusive. No consistency was observed when migrants moved to and from countries with high or low asthma, and no differences were observed in the level of bronchial responsiveness or atopy. In a recent editorial, it was stated that, in a civilized society, it is important that all those in need of healthcare should have equal access to it and benefit equally from that which is available 23. Very importantly, the access to healthcare by migrants with symptoms of asthma seems no different to the nonmigrant population.
A. Tobias was a receiver of the 1999 GlaxoWellcome Summer Fellowship in Epidemiology based at Greenford, UK. The authors are grateful to the late C. Baya and M. Hallen for their help during the study and to K. Vuylsteek and the members of the Comité d'Actions Concertées for their support. The co-ordination of this work was supported by the European Commission. Financial support: Allen and Hanbury's, Australia; Belgian Science Policy Office, National Fund for Scientific Research; Ministère de la Santé, Glaxo France, Insitut Pneumologique d'Aquitaine, Contrat de Plan Etat-Région Languedoc-Rousillon, CNMATS, CNMRT (90MR/10, 91AF/6), Ministre delegué de la santé, RNSP, France; GSF, and the Bundesminister für Forschung und Technologie, Bonn, Germany; The Greek Secretary General of Research and Technology, Fisons, Astra and Boehringer-Ingelheim; Bombay Hospital Trust, India; Ministero dell'Università e della Ricerca Scientifica e Tecnologica, CNR, Regione Veneto grant RSF n. 381/05.93, Italy; Asthma Foundation of New Zealand, Lotteries Grant Board, Health Research Council of New Zealand; Norwegian Research Council project no. 101422/310; Glaxo Farmacêutica Lda, Sandoz, Portugal; Ministero Sanidad y Consumo FIS (grants #91/0016060/00E-05E and #93/0393), and grants from Hospital General de Albacete, Hospital General Juan Ramón Jiménenz, Consejeria de Sanidad Principado de Asturias, Spain; The Swedish Medical Research Council, the Swedish Heart Lung Foundation, the Swedish Association against Asthma and Allergy; Swiss National Science Foundation grant 4026-28099; National Asthma Campaign, British Lung Foundation, Dept of Health, South Thames Regional Health Authority, UK; USA Dept of Health, Education and Welfare Public Health Service (grant #2 S07 RR05521-28). Co-ordinating Centre (London, UK): P. Burney, S. Chinn, C. Luczynska, D. Jarvis, E. Lai. Project Management Group: P. Burney (Project leader) S. Chinn, C. Luczynska, D. Jarvis, P. Vermeire (Antwerp), H. Kesteloot (Leuven), J. Bousquet (Montpellier), D. Nowak (Hamburg), the late J. Prichard (Dublin), R. de Marco (Verona), B. Rijcken (Groningen), J.M. Anto (Barcelona), J. Alves (Oporto), G. Boman (Uppsala), N. Nielsen (Copenhagen), P. Paoletti (Pisa). Participating Centres: W. Popp (Vienna, Austria); M. Abramson, J. Kutin (Melbourne, Australia); P. Vermeire, F. van Bastelaer (Antwerp South, Antwerp Central, Belgium); J. Bousquet, J. Knani (Montpellier, France), F. Neukirch, R. Liard (Paris, France), I. Pin, C. Pison (Grenoble, France), A. Taytard (Bordeaux, France); H. Magnussen, D. Nowak (Hamburg, Germany); H-E. Wichmann, J. Heinrich (GSF Institute of Epidemiology, Erfurt, Germany); N. Papageorgiou, P. Avarlis, M. Gaga, C. Marossis (Athens, Greece); T. Gislason D. Gislason (Reykjavik, Iceland); J. Prichard, S. Allwright, D. MacLeod (Dublin, Ireland); M. Bugiani, C. Bucca, C. Romano (Turin, Italy) R. de Marco, V. Lo Cascio, C. Campello (Verona, Italy) A. Marinoni, I. Cerveri, L. Casali (Pavia, Italy); B. Rijcken, A. Kremer (Groningen, Bergen-op-Zoom, Geleen, the Netherlands); J. Crane, S. Lewis (Wellington, Christchurch, Hawkes Bay, New Zealand); A. Gulsvik, E. Omenaas (Bergen, Norway); J.A. Marques, J. Alves (Oporto, Portugal); Spain: J.M. Antó, J. Sunyer, F. Burgos, J. Castellsagué, J. Roca, J.B. Soriano, A. Tobías (Barcelona, Spain), N. Muniozguren, J. Ramos González, A. Capelastegui (Galdakao, Spain) J. Castillo, J. Rodriguez Portal (Seville, Spain), J. Martinez-Moratalla, E. Almar (Albacete, Spain) J. Maldonado Pérez, A. Pereira, J. Sánchez (Huelva, Spain), J. Quiros, I. Huerta, F. Pavo (Oviedo, Spain); G. Boman, C. Janson, E. Björnsson (Uppsala, Sweden), L. Rosenhall, E. Norrman, B. Lundbäck (Umeå, Sweden), N. Lindholm, P. Plaschke (Göteborg, Sweden); U. Ackermann-Liebrich, N. Künzli, A. Perruchoud (Basel, Switzerland); M. Burr, J. Layzell (Caerphilly, UK), R. Hall (Ipswich, UK), B. Harrison (Norwich, UK), J. Stark (Cambridge, UK); S. Buist, W. Vollmer, M. Osborne (Portland, USA).
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