COPE: Characterisation of COPD Exacerbations using Environmental Exposure Modelling

The aim of this research is to reduce the frequency of hospital and GP visits by patients with chronic obstructive pulmonary disease (COPD). This will be achieved by utilising a combination of miniature sensors that measure an individual's exposure to air pollution, mathematical models that predict air pollution at any location in a city and people's GP health records.

Despite substantial evidence of the adverse health effects of air pollution, ranging from respiratory symptoms through to cancer and cardiovascular mortality, gaps and uncertainties exist in our understanding of why this happens. This has been attributed to over-simplified estimates of how much air pollution (and other environmental stress) individuals are exposed to as they go about their daily lives. This project addresses this limitation by bringing together two fields of research that have made rapid advancements in recent years - time-activity exposure models and personal pollution sensors. The research will be applied to a public health challenge requiring urgent knowledge advancement; prediction and management of COPD exacerbations.

COPD patients are at risk of severe episodes of deterioration - 'exacerbations'. Exacerbations are the second commonest cause of adult emergency medical hospital admission in the UK and are associated with shortened lives and decreased quality of life.

The first phase of the study will comprise the largest real time patient exposure measurement campaign yet carried out in the UK. Micro pollution, temperature and humidity sensors will be carried by 200 COPD patients for six months, with movements tracked by satellite navigation (GPS). During this period patients will keep records of symptoms relating to their condition (such as breathlessness, cough and wheeze) on diary cards and take daily exhaled breath flow tests. We will use this extensive measurement dataset to relate COPD symptoms and exacerbations to air pollution, temperature and humidity levels and activities such as travelling, cooking and exposure to tobacco smoke.

The measurements will then be used to assess and improve the performance of a high resolution 'time-activity' exposure model recently developed for London. Time-activity computer models allow the calculation of an individual's exposure to pollution as they move about a city throughout the day. However, their accuracy is unproven. The pollution measurements taken during the first phase of the study will provide a means of testing the performance of the exposure model by comparing modelled and measured exposure estimates for the 200 COPD patients.

Links between COPD exacerbations and environmental exposure identified in the first phase will be combined with the exposure model validated in the second phase to create a new model for predicting COPD exacerbations. The performance of this model will be evaluated by comparing modelled predictions against GP and hospital records of exacerbations between 2005 and 2011.

If the predictive performance of this model is proven, it presents a means of forming a validated COPD forecasting tool for public health providers in London. The predictive algorithms used in the model will be made available for application across the UK, providing an opportunity for the development of a national COPD forecasting service with proven performance in predicting increased risk of exacerbations.

The final project outcome will be the production of a patient-orientated report describing associations between environmental exposure and COPD symptoms, clearly illustrating how COPD patients can adjust their behaviour to reduce their risk of exacerbation and improve their quality of life.

The research will incorporate an extended cohort monitoring campaign, validation of an existing exposure model and development of a predictive model for COPD exacerbations evaluated against historical electronic health records.

A miniature personal sensor unit will be manufactured for the study from a prototype developed at the University of Cambridge. The units will monitor GPS position, temperature, humidity, CO, NO, NO2, O3, PM10 and PM2.5.

Three 6-month cohort monitoring campaigns will be carried out, each including of 65 COPD patients. Patients will be asked to carry the sensor at all times, take peak flow measurements each morning and fill out a diary card noting any exacerbations or worsening of symptoms.

Measurements from each monitor will be collated into a central database and undergo a series of QA/QC checks and scaling processes. Pollutant ratios will be used to characterise specific pollution sources and patient activities. Statistically significant associations will be explored relating environmental exposure to exacerbations and symptoms.

The field campaign dataset will be used to validate a time-activity exposure model developed at King's College London. Modelled estimates of personal environmental exposure will be compared to measured pollutant exposure and performance for different pollutants and micro-environments assessed.

Improved health associations will be combined with the validated exposure model to create a predictive model for COPD exacerbations across London. Spatial and temporal patterns of recorded exacerbations extracted from historical CPRD, HES and ONS records will be compared to model risk estimates, with the aim of deriving predictive algorithms for future hospitalisations.

The findings of the study will be adapted for application on a national scale and disseminated to healthcare providers. The predictive algorithms will facilitate the development of a validated national COPD forecasting system.

Patients and health care providers will benefit from this research. Currently COPD costs the NHS £500 million yearly and exacerbations are the second commonest cause of adult emergency medical hospital admission. Exacerbations have an enormous effect on patients, leading to days lost at work, loss of independence, decrease in lung function, poorer quality of life and increased mortality. Understanding more about the associations between environmental exposures and exacerbations will allow for development of forecasting models that can be used to predict times of increased exacerbation risk. This will aid health care providers and allow more accurate planning and allocation of resources. This is turn will reduce costs for the NHS. It will aid patients as it may provide an opportunity to alter behaviour and to prevent exacerbations from occurring.

The research will provide methods for strengthening the mechanistic and epidemiological links between urban air pollution and the diverse associated health outcomes. It will also help provide validated tools for demonstrating how personal exposure to air pollution varies between activities and across an urban area. Consequently, all those who live or work in urban areas will benefit from this work.

By providing a more robust evidence base, policy makers will be able to take more targeted and efficient decisions on reducing environmental risk. Members of the public will be able to make more informed decisions on how to minimise their own risks, improving health and quality of life.
The project deliverables are designed to be output in a format that has the potential for impact on these communities soon after the research is complete. The communications plan, which involves direct engagement with community, health care providers and policy makers, will ensure that such impact is realised in a short timescale.