Migration and asthma medication in international adoptees and immigrant families in Sweden

Abstract

Background: Studies of asthma in migrant populations illustrate the effects of environmental changes.

Objective: In this register study we investigated the importance of exposure to a western lifestyle in different phases of development in Swedish residents with an origin in regions in the world where asthma usually is less prevalent.

Methods: The study population comprised 24,252 international adoptees, 47,986 foreign-born and 40,971 Swedish-born with foreign-born parents and 1,770,092 Swedish-born residents with Swedish-born parents (age 6-25 years). Purchased prescribed inhaled corticosteroids (ICS) during 2006 were used as an indicator of asthma.

Results: International adoptees and children born in Sweden by foreign-born parents had three- to fourfold higher rates of asthma medication compared with foreign-born children. The odds ratios (ORs) of asthma medication declined persistently with age at immigration. For adoptees the ORs compared with infant adoptees were 0.78 [95% confidence interval (CI) 0.71-0.85] for those adopted at 1-2 years, 0.51 (0.42-0.61) at 3-4 years and 0.35 (0.27-0.44) after 5 or more years of age. Corresponding ORs for foreign-born children with foreign-born parents immigrating at 0-4 years, at 5-9 years, at 10-14 years and at 15 years or more were 0.73 (0.63-0.86), 0.56 (CI 0.46-0.68) and 0.35 (CI 0.28-0.43), respectively. The ORs were only marginally affected by adjustment for region of birth and socio-economic indicators.

Conclusions and clinical relevance: Age at immigration is a more important determinant of purchased ICS than population of origin. This indicates the importance of environmental factors for asthma in schoolchildren and young adults.