Abstract
BackgroundRecent studies have demonstrated marked international variations in the prevalence of asthma, but less is known about ethnic variations in asthma epidemiology within individual countries and in particular the impact of migration on risk of developing asthma. Recent within country comparisons have however revealed that despite originating from areas of the world with a low risk for developing asthma, South Asian and Afro-Caribbean people in the UK are significantly (3× and 2× respectively) more likely to be admitted to hospital for asthma related problems than Whites.MethodsUsing data from the Fourth National Study of Morbidity Statistics in General Practice, a one-percent broadly representative prospective cohort study of consultations in general practice, we investigated ethnic variations in incident asthma consultations (defined as new or first consultations), and compared consultation rates between those born inside and outside the UK (migrant status). Logistic regression models were used to examine the combined effects of ethnicity and migration on asthma incident consultations.ResultsResults showed significantly lower new/first asthma consultation rates for Whites than for each of the ethnic minority groups studied (mean age-adjusted consultation rates per 1000 patient-years: Whites 26.4 (95%CI 26.4, 26.4); South Asians 30.4 (95%CI 30.3, 30.5); Afro-Caribbeans 35.1 (95%CI 34.9, 35.3); and Others 27.8 (27.7, 28.0). Within each of these ethnic groups, those born outside of the UK showed consistently lower rates of incident asthma consultations. Modelling the combined effects of ethnic and migrant status revealed that UK-born South Asians and Afro-Caribbeans experienced comparable risks for incident GP consultations for asthma to UK-born Whites. Non-UK born Whites however experienced reduced risks (adjusted OR 0.82, 95%CI 0.69, 0.97) whilst non-UK born South Asians experienced increased risks (adjusted OR 1.33, 95%CI 1.04, 1.70) compared to UK-born Whites.ConclusionThese findings strongly suggest that ethnicity and migration have significant and independent effects on asthma incidence. The known poorer asthma outcomes in UK South Asians and Afro-Caribbeans may in part be explained by the offspring of migrants experiencing an increased risk of developing asthma when compared to UK-born Whites. This is the first study to find heterogeneity for incident asthma consultations in Whites by migrant status.
Highlights
The International Study of Asthma and Allergies in Childhood (ISAAC) and European Community and Respiratory Health Survey (ECRHS) have revealed marked international variations in the prevalence of asthma, with populations living in economically-developed countries experiencing the highest prevalence rates [1,2]
We hypothesised that the incidence of asthma episodes would vary between ethnic groups with those born in low risk regions experiencing a lower incidence than those born in the UK
Study sample Our study sample consisted of patients included in the Fourth National Study of Morbidity Statistics in General Practice (MSGP4), a year long prospective cohort study during the period September 1991 – August 1992 of more than half a million patients registered with 60 general practices in England and Wales [9]
Summary
The International Study of Asthma and Allergies in Childhood (ISAAC) and European Community and Respiratory Health Survey (ECRHS) have revealed marked international variations in the prevalence of asthma, with populations living in economically-developed countries experiencing the highest prevalence rates [1,2]. In contrast to marked international variations in the prevalence of asthma, a recent systematic review and metaanalysis of epidemiological studies within the UK has found that despite originating from low risk areas internationally, South Asians and Afro-Caribbeans experience significantly poorer asthma outcomes than do Whites [3]. Possible reasons for these poorer outcomes could include differences in asthma incidence, severity, management and/or health seeking behaviour between ethnic groups [4,5,6,7,8]. We hypothesised that the incidence of asthma episodes would vary between ethnic groups with those born in low risk regions experiencing a lower incidence than those born in the UK (a very high risk region)
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