Study protocol: the effects of air pollution exposure and chronic respiratory disease on pneumonia risk in urban Malawian adults - the Acute Infection of the Respiratory Tract Study (The AIR Study)

BACKGROUND Pneumonia is the 2nd leading cause of years of life lost worldwide and is a common cause of adult admissions to hospital in sub-Saharan Africa. Risk factors for adult pneumonia are well characterised in developed countries, but are less well described in sub-Saharan Africa where HIV is a major contributing factor. Exposure to indoor and outdoor air pollution is high, and tobacco smoking prevalence is increasing in sub-Saharan Africa, yet the contribution of these factors to the burden of chronic respiratory diseases in sub-Saharan Africa remains poorly understood. Furthermore, the extent to which the presence of chronic respiratory diseases and exposure to air pollution contribute to the burden of pneumonia is not known. DESIGN The Acute Infection of the Respiratory Tract Study (The AIR Study) is a case-control study to identify preventable risk factors for adult pneumonia in the city of Blantyre, Malawi. Cases will be adults admitted with pneumonia, recruited from Queen Elizabeth Central Hospital, the largest teaching hospital in Malawi. Controls will be adults without pneumonia, recruited from the community. The AIR Study will recruit subjects and analyse data within strata defined by positive and negative HIV infection status. All participants will undergo thorough assessment for a range of potential preventable risk factors, with an emphasis on exposure to air pollution and the presence of chronic respiratory diseases. This will include collection of questionnaire data, clinical samples (blood, urine, sputum and breath samples), lung function data and air pollution monitoring in their home. Multivariate analysis will be used to identify the important risk factors contributing to the pneumonia burden in this setting. Identification of preventable risk factors will justify research into the effectiveness of targeted interventions to address this burden in the future. DISCUSSION The AIR Study is the first study of radiologically confirmed pneumonia in which air pollution exposure measurements have been undertaken in this setting, and will contribute important new information about exposure to air pollution in urban SSA. Through identification of preventable risk factors, the AIR Study aims to facilitate future research and implementation of targeted interventions to reduce the high burden of pneumonia in SSA.