title: Long-term exposure to air pollution and asthma hospitalisations in older adults: a cohort study.
abstract: BACKGROUND
  Exposure to air pollution in early life contributes to the burden of childhood asthma, but it is not clear whether long-term exposure to air pollution can lead to asthma onset or progression in adulthood.
  
  
  OBJECTIVE
  The authors studied the effect of exposure to traffic-related air pollution over 35 years on the risk for asthma hospitalisation in older people.
  
  
  METHODS
  57 053 participants in the Danish Diet, Cancer and Health cohort, aged 50-65 years at baseline (1993-1997), were followed up for first hospital admission for asthma until 2006, and the annual nitrogen dioxide (NO(2)) levels were estimated as a proxy of the exposure to traffic-related air pollution at the residential addresses of the participants since 1971. The association between NO(2) and hospitalisation for asthma was modelled using Cox regression, for the full cohort and in people with and without previous hospitalisations for asthma, and the effect modification by comorbid conditions was assessed.
  
  
  RESULTS
  During 10.2 years' median follow-up, 977 (1.9%) of 53 695 eligible people were admitted to hospital for asthma: 821 were first-ever admissions and 176 were readmissions. NO(2) levels were associated with risk for asthma hospitalisation in the full cohort (HR and 95% CI per IQR, 5.8 μg/m(3): 1.12; 1.04-1.22), and for first-ever admissions (1.10; 1.01-1.20), with the highest risk in people with a history of asthma (1.41; 1.15-2.07) or chronic obstructive pulmonary disease (COPD) (1.30; 1.07-1.52) hospitalisation.
  
  
  CONCLUSIONS
  Long-term exposure to traffic-related air pollution increases the risk for asthma hospitalisation in older people. People with previous asthma or COPD hospitalisations are most susceptible.
authors: Institute of Cancer Epidemiology, Danish Cancer Society, Strandboulevarden 49, Copenhagen 2100, Denmark. zorana@cancer.dk
authors: Zorana Jovanovic
authors: ZJ
authors: Andersen
authors: Klaus
authors: K
authors: Bønnelykke
authors: Martin
authors: M
authors: Hvidberg
authors: Steen S
authors: SS
authors: Jensen
authors: Matthias
authors: M
authors: Ketzel
authors: Steffen
authors: S
authors: Loft
authors: Mette
authors: M
authors: Sørensen
authors: Anne
authors: A
authors: Tjønneland
authors: Kim
authors: K
authors: Overvad
authors: Ole
authors: O
authors: Raaschou-Nielsen
mesh_terms: D000368:Aged; D000393:Air Pollutants / Q000009:adverse effects*; D001249:Asthma / Q000453:epidemiology* / Q000628:therapy; D003718:Denmark / Q000453:epidemiology; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization / Q000639:trends*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors
chemical_list: D000393:Air Pollutants