title: Current asthma contributes as much as smoking to chronic bronchitis in middle age: a prospective population-based study.
abstract: OBJECTIVE
  Personal smoking is widely regarded to be the primary cause of chronic bronchitis (CB) in adults, but with limited knowledge of contributions by other factors, including current asthma. We aimed to estimate the independent and relative contributions to adult CB from other potential influences spanning childhood to middle age.
  
  
  METHODS
  The population-based Tasmanian Longitudinal Health Study cohort, people born in 1961, completed respiratory questionnaires and spirometry in 1968 (n=8,583). Thirty-seven years later, in 2004, two-thirds responded to a detailed postal survey (n=5,729), from which the presence of CB was established in middle age. A subsample (n=1,389) underwent postbronchodilator spirometry between 2006 and 2008 for the assessment of chronic airflow limitation, from which nonobstructive and obstructive CB were defined. Multivariable and multinomial logistic regression models were used to estimate relevant associations.
  
  
  RESULTS
  The prevalence of CB in middle age was 6.1% (95% confidence interval [CI]: 5.5, 6.8). Current asthma and/or wheezy breathing in middle age was independently associated with adult CB (odds ratio [OR]: 6.2 [95% CI: 4.6, 8.4]), and this estimate was significantly higher than for current smokers of at least 20 pack-years (OR: 3.0 [95% CI: 2.1, 4.3]). Current asthma and smoking in middle age were similarly associated with obstructive CB, in contrast to the association between allergy and nonobstructive CB. Childhood predictors included allergic history (OR: 1.3 [95% CI: 1.1, 1.7]), current asthma (OR: 1.8 [95% CI: 1.3, 2.7]), "episodic" childhood asthma (OR: 2.3 [95% CI: 1.4, 3.9]), and parental bronchitis symptoms (OR: 2.5 [95% CI: 1.6, 4.1]).
  
  
  CONCLUSIONS
  The strong independent association between current asthma and CB in middle age suggests that this condition may be even more influential than personal smoking in a general population. The independent associations of childhood allergy and asthma, though not childhood bronchitis, as clinical predictors of adult CB raise the possibility of some of this burden having originated in childhood.
authors: Allergy and Lung Health Unit, Center for Epidemiology and Biostatistics, The University of Melbourne.
authors: Shyamali C
authors: SC
authors: Dharmage
authors: Allergy and Lung Health Unit, Center for Epidemiology and Biostatistics, The University of Melbourne; Institute for Breathing and Sleep (IBAS), Melbourne, VIC.
authors: Jennifer L
authors: JL
authors: Perret
authors: Allergy and Lung Health Unit, Center for Epidemiology and Biostatistics, The University of Melbourne.
authors: John A
authors: JA
authors: Burgess
authors: Allergy and Lung Health Unit, Center for Epidemiology and Biostatistics, The University of Melbourne.
authors: Caroline J
authors: CJ
authors: Lodge
authors: "Breathe Well" Center of Research Excellence for Chronic Respiratory Disease and Lung Ageing, School of Medicine, University of Tasmania, Hobart, TAS.
authors: David P
authors: DP
authors: Johns
authors: Inflammation and Infection Research, Faculty of Medicine, University of New South Wales, Sydney, NSW.
authors: Paul S
authors: PS
authors: Thomas
authors: Allergy and Lung Health Unit, Center for Epidemiology and Biostatistics, The University of Melbourne; Cancer Epidemiology Center, Cancer Council Victoria, Melbourne, VIC, Australia.
authors: Graham G
authors: GG
authors: Giles
authors: Allergy and Lung Health Unit, Center for Epidemiology and Biostatistics, The University of Melbourne; Department of Public Health, Seoul National University, Seoul, South Korea.
authors: John L
authors: JL
authors: Hopper
authors: Allergy, Immunology and Respiratory Medicine, The Alfred Hospital, Melbourne; School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC.
authors: Michael J
authors: MJ
authors: Abramson
authors: "Breathe Well" Center of Research Excellence for Chronic Respiratory Disease and Lung Ageing, School of Medicine, University of Tasmania, Hobart, TAS; School of Medicine, University of Tasmania, Hobart, TAS, Australia.
authors: E Haydn
authors: EH
authors: Walters
authors: Allergy and Lung Health Unit, Center for Epidemiology and Biostatistics, The University of Melbourne.
authors: Melanie C
authors: MC
authors: Matheson
mesh_terms: D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D029481:Bronchitis, Chronic / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008168:Lung / Q000503:physiopathology*; D008297:Male; D015999:Multivariate Analysis; D016017:Odds Ratio; D015995:Prevalence; D011379:Prognosis; D011446:Prospective Studies; D012135:Respiratory Sounds; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology / Q000503:physiopathology; D013147:Spirometry; D011795:Surveys and Questionnaires; D013648:Tasmania / Q000453:epidemiology; D013997:Time Factors
keywords: allergy history; current asthma; nonobstructive chronic bronchitis; obstructive chronic bronchitis; personal smoking