title: Age-of-asthma onset as a determinant of different asthma phenotypes in adults: a systematic review and meta-analysis of the literature.
abstract: Age-of-asthma onset is often used to distinguish different adult asthma phenotypes; however, similarities and differences between early- and late-onset adult asthma have not been summarized to date. Of the 2921 records found, we identified 12 studies comparing early- and late-onset current asthma in adults. Age 12 was most commonly used to delineate the two age-of-onset phenotypes. Adults with early-onset current asthma were more likely to be atopic and had a higher frequency of asthma attacks, whereas adults with late-onset disease were more likely to be female, smokers and had greater levels of spirometrically defined fixed airflow obstruction. The prevalence of severe asthma was similar in both groups, and, in general, there were few phenotypic differences between severe asthmatics regardless of age of onset. Findings for several key characteristics, including lung function, were inconsistent between studies. Overall, there appears to be distinctive phenotypic differences with age of asthma onset. Although early-onset adult asthma is likely more attributable to atopy and potentially genetic factors, late-onset adult asthma appears to be more related to environmental risk factors, and so may be better targeted by preventive strategies. More detailed research is required to better characterize these phenotypes and to clarify potential clinical implications.
authors.affiliation: Allergy and Lung Health Unit, Centre of Epidemiology and Biostatistics, School of Population and Global Health, The University of Melbourne, 207 Bouverie Street, Carlton, Vic 3052, Australia.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Tan
authors.forename: Eugene Haydn
authors.initials: EH
authors.lastname: Walters
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Perret
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Lodge
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Lowe
authors.forename: Melanie C
authors.initials: MC
authors.lastname: Matheson
authors.forename: Shyamali C
authors.initials: SC
authors.lastname: Dharmage
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics / Q000503:physiopathology* / Q000628:therapy; D002648:Child; D015897:Comorbidity; D004777:Environment; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008019:Life Style; D008168:Lung / Q000503:physiopathology*; D008297:Male; D016017:Odds Ratio; D010641:Phenotype; D015995:Prevalence; D011379:Prognosis; D012307:Risk Factors; D012737:Sex Factors; D055815:Young Adult
keywords: adult asthma; age of onset; early-onset; late-onset; phenotypes