Worldwide trends in asthma mortality.

Statistics for deaths from asthma yield widely variable mortality rates between countries. Validation studies show significant inaccuracies in certification of cause of death in older subjects, and probable underreporting of asthma deaths in some countries, explaining some of the international differences noted. The introduction of the ninth revision of the World Health Organisation International Classification of Diseases brought a step increase in reported asthma mortality rates in 1979, but the last decade has seen a gradual increase in mortality rates in many countries, especially in young people, not explained by this change in code. Diagnostic transfer does not adequately explain these increases. Individuals at risk of death from asthma are more likely to be non-caucasian, non-compliant, and young, with a history of previous life-threatening episodes, hospital admissions, and precipitous attacks. Studies of circumstances of death have emphasized overreliance on beta-agonists and underuse of corticosteroids as two primary deficiencies in management, but there remains debate about the causality of the association between increased asthma mortality and increased usage of beta-agonists. The gradual increase in asthma mortality seen in New Zealand over the last 40 years, with episodic increases in the rising baseline, together with similar but more gradual changes in other countries, raises concerns about whether current treatment practices may adversely affect asthma severity and mortality. Further studies are required to validate asthma mortality statistics, and to establish causation of deaths.