Projects

Goal: To project the impact of air pollution on the burden of asthma in Canada and evaluate the cost-effectiveness of portable HEPA filter air cleaners as a climate adaptation strategy

Background: Over three million deaths globally were attributed to air pollution in 2019, including 15,300 Canadians. People with asthma are particularly susceptible to air pollution, as ambient fine particulate matter (PM2.5) and gaseous pollutants (O3, NO2, and SO2) are robustly linked to the incidence of childhood asthma, poor asthma control, and asthma exacerbations, resulting in 2.7 million additional asthma symptom days, and 35 million acute respiratory exacerbations in Canada every year. Cost-effectiveness analysis is widely used in health policy and clinical decision making to assess the value of health interventions, but has rarely been applied to evaluate climate adaptation strategies. This is a major barrier to implementation, as funding for these interventions is likely to fall to health authorities who will require evidence of cost-effectiveness.

Objective 1): Integrate air quality projections into an existing disease simulation model of asthma in the general Canadian population to project the impact of future levels of air pollution.

• Objective 1.1: Predict the incidence and prevalence of asthma from 2020-2036.
• Objective 1.2: Calculate the fraction of preventable asthma cases if air pollution were held to baseline levels observed from 2015-2019.

Objective 2): Evaluate the cost-effectiveness of a portable HEPA filter air cleaner distribution program for reducing asthma incidence and complications over a 16-year time horizon.

We will evaluate both objectives in the Canadian general population and in subgroups defined by prevalent asthma, age, sex, and geographically-linked material deprivation, social deprivation, and marginalization.

Funding: CIHR Catalyst Grant: Chief Public Health Officer (CPHO) Report 2022: Mobilizing Public Health Action on Climate Change in Canada

We are committed to involving patients in all stages of development of the asthma policy model. LEAP has been used as a case study to develop methods for patient and public involvement (PPI) in modeling. We maintain a patient advisory council who is deeply involved in decisions on what and how we model, and our interpretation of results. This work is informed by philosophical theory on managing values in health economic modelling. Our approach to PPI and application to LEAP is described in an upcoming manuscript (currently under review).

An upcoming LEAP initiative focuses on smoking cessation as a strategy to reduce secondhand smoke exposure and the burden of asthma in Canada. In order to evaluate smoking cessation as an asthma prevention policy, the project engages diverse participants—including patients, clinicians, policy makers, and funders—to shape the model development and evaluate its impact. It also explores how stakeholder involvement influences model outcomes and public trust, helping inform future policy and funding decisions.

Funding: SSHRC, CIHR, and Michael Smith Health Research BC through the Research on Research Joint Initiative.

Background: Infant antibiotic use is associated with increased risk of asthma. This link can be attributed to the deleterious impact of antibiotics on the maturation of the infant gut microbiome, the composition of which plays a crucial role in healthy immunological development. Disruption of this process can lead to hyperinflammatory immune responses later in childhood and the development of allergic diseases, such as asthma, in later life. We examined the population impact of antibiotic exposure in the first year of life on the burden of pediatric asthma in British Columbia, Canada, using simulation modeling.

Methods: We performed a Bayesian meta-analysis of empirical studies to construct dose-response equations between antibiotic exposure in the first year of life and pediatric (<19 years of age) asthma. We used administrative health data to document trends in infant (<1 year of age) antibiotic use in British Columbia during 2001 and 2018 (the study period). LEAP was used to estimate asthma-related outcomes under three scenarios pertaining to the trends in antibiotic use during the study period: (1) observed trends, (2) flat trend in which the prescription rate remained at the 2001 value, and (3) intermediate trends midway between these two. We reported cumulative person-years with asthma, cumulative asthma incidence, and cumulative asthma exacerbations among the pediatric population during the study period.

Results: There were 773,160 live births during the study period, with an average antibiotic prescription rate of 523 per 1,000 infants in the first year of life. The prescription rate decreased by 71.5% during the study period. In Scenario 1, there were 1,982,861 person-years with asthma, 183,392 asthma incident cases, and 383,072 exacerbations. Had the antibiotic exposure remained at the 2001 values (Scenario 2), there would have been additional 37,213 person-years with asthma, 10,053 asthma incident cases, and 23,280 exacerbations. Had the decline been half of the observed trend (Scenario 3), there would have been additional 20,318 person-years with asthma, 5,486 asthma incident cases, and 12,728 exacerbations. At least 80% of the excess burden in each outcome was attributable to the younger pediatric population of <10 years of age.

Conclusions: The decline in infant antibiotic exposure has resulted in a substantial reduction in the burden of asthma in British Columbia. Such benefits should be considered when evaluating the value proposition of initiatives aimed at reducing unnecessary antibiotic exposure in early life.