No further increase of incidence of asthma: Incidence, remission and relapse of adult asthma in Sweden
Received 10 April 2008; accepted 6 July 2008. published online 29 August 2008.
Summary
Background
Knowledge about time trends of disease patterns in society is essential for planning and prioritizing health care resources. Longitudinal population-based studies on asthma are scarce but provide an opportunity to assess incidence, remission and relapse of asthma, and their determinants, which were the objectives of the present study.
Methods
A postal questionnaire was sent on two occasions, 1996 and 2006, to a randomly selected sample of subjects aged 20–69 years in 1996. The response rates were 72% and 83%, respectively, and in total 4479 subjects participated in both surveys. The questionnaire included questions on asthma, respiratory symptoms and possible determinants. Logistic regression was used to assess determinants.
Results
Cumulative incidence of asthma was 2.4% (men 1.9%; women 2.8%, p=0.06). Family histories of asthma (OR 2.31, CI 95% 1.42–3.76), rhinitis (OR 2.25, CI 95% 1.43–3.53) and being an ex-smoker (OR 2.17, CI 95% 1.27–3.71) were determinants for incident asthma. The 10-year remission of asthma was 14.6% and inversely associated with rhinitis. Relapse was found in 38% of eligible subjects.
Conclusions
The current study with high participation rates concludes that the incidence of asthma among adults has been stable in Sweden for the past two decades. Remission was associated with mild disease at study start. Relapse in adults has rarely been reported previously and provide new insight in the course of asthma. Low remission and high relapse further support the view of asthma as a chronic disease; possibly representing fluctuations of the disease over time.
aDepartment of Internal Medicine/Respiratory Medicine and Allergology, Sahlgrenska Academy, University of Gothenburg, Guldhedsgatan 10A, SE-413 46 Gothenburg, Sweden
bObstructive Lung Disease In Northern Sweden (OLIN) Studies, Department of Medicine, Sunderby Central Hospital of Norrbotten, Luleå, Sweden
cDepartment of Public Health and Clinical Medicine/Environmental Medicine and Occupation, University of Umeå, Sweden
dLung and Allergy Research, National Institute of Environmental Medicine, Karolinska Institutet, Stockholm Sweden
ABSTRACT