Seasonal variation in childhood asthma hospitalisations in Finland, 1972-1992

All hospital treatment periods caused by asthma in children under 15 years in Finland during 1972-1992 were examined. The data were obtained from the Hospital Discharge Register, covering all hospitalisations in Finland. A total of 59,624 asthma related treatment periods were recorded. The monthly variation in hospitalisations peaked in May (35.6% above the trend) and in autumn and early winter (41.3% above the trend in October), whereas the monthly variations were low in late winter and in summer. The overall profile of seasonal variation was similar in both sexes, although admissions were lower for boys than for girls in winter and higher in autumn. The average monthly deviation was highest in the age group 0-4 years in May, 42.8% above the trend, and highest in the age group 5-9 years in October, 53.9% above the trend. Closer examination of the seasonal variation gives indirect information on possible trigger factors for acute asthma. Conclusion A clear seasonal variation could be observed in childhood asthma hospital admissions, together with age and sex-related differences in this seasonality. Preventive treatment for asthma should be used effectively in order to avoid acute attacks leading to hospitalisation in children who are allergic to birch pollen and also at times of viral respiratory infections.