Has the increase in the prevalence of asthma and respiratory symptoms reached a plateau in Stockholm, Sweden?

SETTING

An increase in the prevalence of asthma has previously been reported worldwide. However, the current trend is debatable.

OBJECTIVE

To assess changes in the prevalence of asthma and respiratory symptoms in a defined study area in Stockholm, Sweden, using identical methods.

DESIGN

A questionnaire was sent by mail in 1996 and 2007 to randomly selected subjects aged 20-69 years. On both occasions, 8000 subjects received the questionnaire, with response rates of 72% and 68%, respectively. Questions on asthma, respiratory symptoms, asthma medication and possible determinants were included. Logistic regression analysis was used to assess determinants.

RESULTS

Ever asthma increased from 8.7% in 1996 to 11.0% in 2007 and physician-diagnosed asthma from 7.6% to 9.3%. The proportion of asthma patients reporting one to two symptoms increased by 14% during the study period. There were few significant changes in the prevalence of respiratory symptoms: wheeze in the previous 12 months (15.9-17.3%), wheezing with breathlessness apart from cold (3.2-4.1%) and recurrent wheeze (8.3-6.8%). There was no major difference in the risk factor pattern between the surveys.

CONCLUSION

An increase in the prevalence of asthma with few symptoms as well as an unchanged prevalence of symptoms was demonstrated, which may indicate a change in diagnostic practices.