Migrant status and childhood hospitalizations for asthma and other wheezing disorders

In developed Western settings, asthma is more prevalent among second-generation compared to first-generation migrants. However, these studies are difficult to interpret as they include migrants of various ethnicities and countries of origin.

We assessed the association of parental migrant status with wheezing disorders among children born in Hong Kong, a developed non-Western setting, where many children have migrant parents from mainland China of the same ethnicity.

We used Cox regression to examine the adjusted associations of parental migrant status with time to first public hospital admission for asthma, bronchitis and bronchiolitis (International Classification of Diseases, Ninth Version Clinical Modification 466, 490 and 493) from 9 days to 12 years in a population-representative birth cohort of 8327 Chinese children in Hong Kong.

Having both parents as migrants was associated with higher risk of hospitalization for asthma and other wheezing disorders, compared to both parents being Hong Kong born (hazard ratio 1.30, 95% confidence interval 1.05-1.60 from 9 days to 6 years), adjusted for type of hospital at birth, parental history of allergies, mother's age at birth, father's age at birth and highest parental education.

In the unique, non-Western context of Hong Kong, second-generation migrants had higher risk of hospitalization for childhood wheezing disorders compared to the native population, particularly before 6 years of age. Further study is required to clarify the underlying mechanisms involved.