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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 - PowerPoint PPT Presentation
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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‘I have no, real or perceived, conflicts of interest that relate to this presentation’
Asthma Chronic inflammatory disease 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:- asthma incidence and prevalence based on self-reports of asthma- losely defined onset, recall/info bias- short air pollution exposure windows
Aim of this study
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) regional background, 2) urban background, & 3) street level contribution
Input for AirGIS model Street/building geometry Street network and traffic data Meteorology
Road centre line
Address point
Building
Road centre line
Address point
Building
GIS Maps building height, street width, open sector
Traffic counts, emission factors, density, speed, types, variation patterns over time
Methods – Air Pollution Exposure
AirGIS Model output: Annual mean NO2 /NOx
concentrations at individual address
NOX (Class)
680000 690000 700000 710000 720000 730000
6140000
6150000
6160000
6170000
6180000
6190000
6200000
6210000
6220000
1 2 3 4 5 6 7 8 9 10
a)
Lille Valby
wind
Leeward Windward
Recirculated pollution
Direct emission
Background pollution
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
Results: Study Population
Cohort Asthma
57 053- 571 cancer before
baseline- 962 missing address or
geocode - 1 236 missing address
- 589 missing info on covariates
Original Cohort
53 695 Study Population
977 (1.9%)
53 143 Asthma-free 821 (1.5%)
552 Previous Asthma
176 (31.9%)
Outcome: Asthma Hospitalization
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 cohort 15.2 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 familial history of asthma, important risk factors for asthma and potential effect modifiers
Lack of work address, activity pattern, indoor air pollution sources, which could have imporved air pollution exposure assesment