Ethnic differences in prevalence of asthma symptoms and bronchial hyperresponsiveness in New Zealand schoolchildren.

Maoris and Pacific Islanders in New Zealand have a higher asthma mortality and hospital admission rates than Europeans. To determine whether difference in asthma prevalence is the major factor underlying these differences in mortality, 2053 Auckland children aged 7-10 years (European 1084, Maori 509, Pacific Islander 460) were randomly sampled from school classes in the Auckland Urban Area, and studied by questionnaire (completed by parents) and histamine inhalation challenge to assess the provocative dose of histamine causing a 20% fall in FEV1 (PD20). Maoris had the highest prevalence rates of respiratory symptoms, and Europeans had rates similar to Pacific Islanders. For "any current wheeze" for example, the prevalence in Maoris was 22.2% compared with 16.1% and 16.3% in the Europeans and Pacific Islanders. The prevalence of diagnosed asthma was similar in the three groups. When bronchial hyperresponsiveness (defined as a PD20 less than or equal to 7.8 mumol histamine) was considered, Europeans had the highest rates (20%), followed by Maoris (13%), and then Pacific Islanders (8.7%). These differences were not accounted for by differences in socioeconomic status, rates of smoking in the home, age, gender, or height. It is concluded that differences in asthma prevalence do not satisfactorily explain the mortality and admission rate differences, although the higher symptom prevalence in the Maoris could be relevant to the higher mortality rate. Maori and Pacific Island children with symptoms of asthma were less likely to be taking prophylactic medication than European children. It is proposed that differences in management are important factors relevant to the increased mortality and morbidity from asthma in Polynesians.