Background Differences between early-onset and late-onset adult asthma have not been comprehensively described using prospective data.
Aims To characterise the differences between early-onset and late-onset asthma in a longitudinal cohort study.
Methods The Tasmanian Longitudinal Health Study (TAHS) is a population-based cohort. Respiratory histories and spirometry were first performed in 1968 when participants were aged 7 (n=8583). The cohort was traced and resurveyed from 2002 to 2005 (n=5729 responses) and a sample, enriched for asthma and bronchitis participated in a clinical study when aged 44 (n=1389).
Results Of the entire TAHS cohort, 7.7% (95% CI 6.6% to 9.0%) had early-onset and 7.8% (95% CI 6.4% to 9.4%) late-onset asthma. Atopy and family history were more common in early-onset asthma while female gender, current smoking and low socioeconomic status were more common in late-onset asthma. The impact on lung function of early-onset asthma was significantly greater than for late-onset asthma (mean difference prebronchodilator (BD) FEV1/FVC −2.8% predicted (−5.3 to −0.3); post-BD FEV1FVC −2.6% predicted (−5.0 to −0.1)). However, asthma severity and asthma score did not significantly differ between groups. An interaction between asthma and smoking was identified and found to be associated with greater fixed airflow obstruction in adults with late-onset asthma. This interaction was not evident in adults with early-onset disease.
Conclusions Early-onset and late-onset adult asthma are equally prevalent in the middle-aged population. Major phenotypic differences occur with asthma age-of-onset; while both share similar clinical manifestations, the impact on adult lung function of early-onset asthma is greater than for late-onset asthma.
- Asthma Epidemiology
- Respiratory Measurement
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MCM and SCD contributed equally.
Contributors Study concept and design: SCD, EHW, MJA, DPJ, GGG and JLH. Acquisition of data: SCD, EHW, MJA, MCM, PST, IF, SM, DPJ and JAB. Analysis and interpretation of data: DJT, SCD, JLP, JAB, JAS, PHR and EHW. Drafting of the manuscript: DJT, JLP, SCD and EHW. Critical revision of the manuscript for important intellectual content: all authors. Statistical analysis: DJT, JLP, JAB, PHR and SCD. Obtained funding: SCD, EHW, SM, MJA, DPJ and JLH. Administrative, technical and material support: SCD. Study supervision: SCD, EHW, JLP and JAB.
Funding Supported by the National Health and Medical Research Council of Australia grant 299901; Clifford Craig Medical Research Trust of Tasmania; Victorian, Queensland and Tasmanian Asthma Foundations and the Australian Lung Foundation.
Competing interests None declared.
Ethics approval The study was approved by the Human Ethics Review Committees at The Universities of Melbourne, Tasmania and New South Wales, the Alfred Hospital, and Royal Brisbane and Women's Hospital Health Service District. Written informed consent was obtained from all participants.
Provenance and peer review Not commissioned; externally peer reviewed.