Outcome and severity of adult onset asthma--report from the obstructive lung disease in northern Sweden studies (OLIN)

Abstract

Background: Studies of longitudinal changes in severity and the long-term outcome of asthma in epidemiological settings are uncommon.

Aim: To assess the outcome of incident asthma in a cohort of subjects who developed asthma after the age of 20 years.

Methods: This is a prospective study of the outcome of 309 subjects with incident asthma being included in a case-referent study based on all adults aged 20-60 years living in three municipalities/towns in Northern Sweden. The subjects fulfilled the criteria for incident asthma defined as onset of symptoms common in asthma within 12 months prior to the study and a verified bronchial variability. In 2003, 250 (81%) of the subjects with asthma were re-examined with structured interview, lung-function test and methacholine test.

Results: At follow-up, 237 (95%) subjects still had an active asthma, i.e. they had symptoms or used asthma medicines. Among those with active asthma, 65% were using inhaled cortico-steroids. Severity grading (GINA 2000) showed that 21% had mild intermittent asthma, 30% mild persistent, 44% moderate persistent, and 5% severe asthma, contrasting to 75% with moderate or severe asthma at entry. Higher age, higher BMI and low lung function were associated with greater asthma severity. Twelve subjects (5%) were in remission. Predictors for remission were non-sensitisation and a normal lung function. Age, sex, BMI, and smoking habits were not significantly different between those in remission and those not.

Conclusions: Remission of adult onset asthma was low. Severity of asthma changed considerably over time, however, the overall change was towards a milder disease probably as a result of treatment.