Long-term exposure to air pollution and asthma hospitalisations in older adults: a cohort study Zorana Jovanovic Andersen 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  subjects, Copenhagen and Aarhus  Interviewed in (baseline)  Age 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 ( ) 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 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 NO 2 /NO x 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  NO 2 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 CohortAsthma cancer before baseline -962 missing address or geocode missing address -589 missing info on covariates Original Cohort Study Population977 (1.9%) Asthma-free821 (1.5%) 552 Previous Asthma176 (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: Descriptive Statistics

Results: Exposure to Air Pollution Median NO 2 for cohort 15.2 µg/m 3 and for asthmatics (n=977) 16.4 µg/m 3

Results: Main Analysis Excluding 452 subjects with prior COPD admissions: 1.11 ( ) 1.10 ( ) 1.29 ( )

Results: Effect Modification

Results: dose-response

Conclusions  The risk for asthma hospitalization in this elderly cohort was significantly positively associated with increasing levels of NO 2 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

Acknowledgements  Thorax