Seasonal variation in asthma hospitalizations and death rates in New Zealand.

OBJECTIVE: The aim of this study was to determine if there is a seasonal pattern to asthma hospitalizations and mortality in New Zealand.
METHODOLOGY: Data for an 18-20 year period were obtained for the whole of New Zealand regarding the number of asthma deaths and hospital discharges in each month, as well as annual population totals (1978-1995 for asthma hospitalizations, 1976-1995 for asthma deaths). Monthly mortality and hospital discharge rates were calculated for the age groups 5-14, 15-44, and those aged 45 years and older. Variation about the mean monthly rates was plotted along a linear timescale to observe the seasonal trend.
RESULTS: In the oldest age group (45+), asthma mortality and hospitalization rates peaked in the winter months (July/August). Among the younger age groups, however, mortality and hospitalizations showed different seasonal patterns; peak hospitalization occurred in the early winter months, with peak mortality in the early summer months.
CONCLUSIONS: Seasonal variations in the asthma hospitalization and death rates in New Zealand are similar to those from the Northern Hemisphere. The peak mortality in summer for the younger age groups is paralleled by a reduction in hospitalizations in this period, indicating that the increase in mortality may be due to problems of access to medical care.