Asthma in the community Observations by the Swiss Sentinel Surveillance Network over a ten year period (1988-1997)

Abstract

Purpose: The overall prevalence and incidence of asthma attacks reported by primary care physicians (general practitioners, general internists and paediatricians) between 1988 and 1997 was assessed. Special attention was paid to the observation of seasonal patterns in different age groups of the consulting population.Methods: About 200 private practice physicians participated in the collection of data each year. Only data from doctors who reported 39 weeks or more each year were included in the analysis. Physicians were recruited on the basis of a stratification by geographic area, sociodemographic characteristics and speciality, with even distributions over the whole country. They represent about 3% of all family practitioners in Switzerland. Weekly attack rates per physician were investigated using time series analysis. Seasonal smoothing was used to visualise and explore the series.Results: Asthma attack rates (all ages) increased from 5.7 attacks per physician (0.18 per 100 consultations) in 1988/1989 to 11.8 (0.22 per 100 consultations) in 1994. The rates then decreased to 8.8 (0.19 per 100 consultations) in 1996 and rose to 10.4 (0.22 per 100 consultations) in 1997. Peak incidence occurred in June (particularly for the 5-16 years age group) and in November (particularly for the 0-4 years age group). Seasonality dwindled with increasing age. Attack rates were highest in January and July in the 46-65 years and above 65 years age groups. An August/September trough was repeatedly found in all age groups. First asthma attacks (registered since 1994) accounted for a third of all asthma attacks. Hospital admission rates, expressed as a percentage of attacks, were low by international standards.Conclusions: Sentinel practices in Switzerland are useful for measuring the asthma morbidity seen in the primary care setting. We observed a rising trend in asthma rates until 1994 and a fluctuating course until 1997. We believe that the temporal changes over time in asthma rates reflect societal changes, with a tendency to early therapeutic interventions by both patients and professionals. Differences in seasonal patterns signal the presence of environmental and age-related diagnostic effects which overlap with virus-induced wheezing, allergic asthma and bronchitis-related broncho-constrictive disorders.