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Long-term exposure to air pollution and asthma hospitalisations in older adults: a cohort study. Zorana Jovanovic Andersen 27.09.2011 ERS. Conflict of interest disclosure
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Long-term exposure to air pollution and asthmahospitalisationsin older adults: a cohort study Zorana Jovanovic Andersen 27.09.2011 ERS Conflict of interest disclosure ‘I have no, real or perceived, conflicts of interest that relate to this presentation’
Asthma • Chronicinflammatorydisease of the airways, characterized by variable and recurring symptoms, reversible airflow obstruction, hyperresponsiveness, bronchospasm.
Background • The prevalence of asthma in older adults is 6-10% in high-income countries, and increasing, including Denmark, where increase in the severity is also documented • The economic burden associated with hospital care, medications, and years of work lost is projected to escalate with increasing numbers of older people with asthma due to enhanced longevity
Background: Asthma & Air Pollution • Short-term exposure to elevated air pollution linked to exacerbation of asthma symptoms (wheezing, coughing, breathlessness) in children and adults, leading to asthma hospitalizations • More studies in children than adults: long-term exposure to air pollution in early life linked to development of asthma • Limited evidence in adults: does long-time/lifetime exposure to air pollution increases risk of asthma development in adult life?
Background: Asthma & Air Pollution Limitations: - asthmaincidence and prevalencebased on self-reports of asthma - loselydefinedonset, recall/info bias - short air pollution exposurewindows
Aim of thisstudy • We studied the association between traffic-related air pollution levels for up to 35 years at the residence and the risk for hospital admission for asthma in an elderly Danish cohort • We tested for an effect modification by lifestyle, education, and co-morbid conditions
Methods - Cohort • Danish Diet, Cancer and Health cohort • 57 053 subjects, Copenhagen and Aarhus • Interviewed in 1993-1997 (baseline) • Age 50-65 years • Linkage to Central Population Registry and Danish Address Database - residential address history (1971) • Linkage to Danish National Patient Register (1979): • first-admission for asthma (ICD-10: J45-46), between baseline (1993-1997) and 27 June 2006 • co-morbidities defined as hospitalizations for COPD (J40-44), ischemic heart disease (I20-25), and stroke (I60-63)
Methods – Air Pollution Exposure • AirGIS dispersion model, sum of: 1) regionalbackground, 2) urbanbackground, & 3) streetlevelcontribution • Input for AirGIS model • Street/building geometry • Street network and traffic data • Meteorology Traffic counts, emission factors, density, speed, types, variation patterns over time GIS Mapsbuildingheight, streetwidth, opensector
Methods – Air Pollution Exposure • AirGIS Model output: • Annual mean NO2 /NOx concentrations at individual address Flow and dispersion inside a street canyon
Methods – Statistical Model • Cox proportional hazards model, left truncation at age at baseline, and right censoring at age at hospital admission for asthma, death, emigration, or 27 June 2006 • NO2 time-dependent variables, log transformed, mean since 1971 until asthma/censoring, estimates per IQR • Confounders: sex, smoking (status, intensity, duration, ETS), occupational exposures, BMI, educational level, fruit consumption • Effect modification: interaction term, Wald-test • Spline (rcs) in R, for dose-repsonse curve
Outcome: AsthmaHospitalization • Objective measure of asthma onset, nationwide register • Not marker of disease onset, but hallmark of asthma progression to a more severe stage or exacerbation • Traditionally confirmed by objective measurements of lung function and reversible airflow obstruction in Danish hospitals • The specificity of asthma as high as 0.98 • Underestimates real asthma burden
Results: Exposure to Air Pollution Median NO2 for cohort15.2 µg/m3 and for asthmatics (n=977) 16.4 µg/m3
Results: Main Analysis Excluding 452 subjects with prior COPD admissions: 1.11 (1.02-1.21) 1.10 (1.01-1.21) 1.29 (1.03-1.60)
Conclusions • The risk for asthma hospitalization in this elderly cohort was significantly positively associated with increasing levels of NO2 assessed over 35 years at their residences • The risk for new asthma hospitalizations about 10% per IQR • The risk was most pronounced for people with a previous asthma 41% per IQR or COPD hospitalization 31% per IQR.
Limitation • No data on atopy, allergy, or familialhistory of asthma, importantrisk factors for asthma and potential effectmodifiers • Lack of workaddress, activity pattern, indoor air pollution sources, whichcould have imporved air pollution exposureassesment
Acknowledgements • Thorax