Background: Three billion people worldwide use solid fuels for cooking and heating their homes. The World Health Organization estimates that the resultant household air pollution causes 6.5 million deaths per year, predominantly in low- and middle-income countries. Despite causing half a million deaths per year from childhood pneumonia, the association between household air pollution and pneumonia in adults - a common cause of morbidity and mortality in sub-Saharan Africa - is not established. Studies of household air pollution are limited by difficulties in quantifying exposure levels, contributing to the relative scarcity of evidence. Addressing these methodological challenges would facilitate efforts to obtain the evidence required to reduce this health burden for the world's poorest populations. Focussing particularly in the sub-Saharan country of Malawi, this thesis aims to explore the challenges regarding exposure measurements in resource poor settings, and to provide evidence regarding the role of household air pollution in pneumonia in adults. Methods: The literature was systematically reviewed to establish the current evidence base for an association between household air pollution and pneumonia in adults. Two prospective studies examining the suitability of potential biomarkers of household air pollution exposure were undertaken: firstly, to establish the feasibility of using airway macrophage particulate load obtained from induced sputum samples as a biomarker; and secondly, to explore whether exhaled carbon monoxide is a suitable biomarker for use in field studies. Finally, a case-control study of HIV-positive and HIV-negative Malawian adults was undertaken to establish the role of household air pollution, and other potential risk factors, in pneumonia. Results: Eight studies regarding household air pollution and acute lower respiratory tract infection were identified, reporting conflicting data and with limited study quality. The two methods used to calculate airway macrophage particulate load were lengthy, complex and unreliable. Exhaled carbon monoxide tests were easy to use and acceptable to participants in Malawi, but were subsequently found to not correlate with measured air pollution exposures. 145 (117 HIV-positive; 28 HIV-negative) cases and 253 (169 HIV-positive; 84 HIV-negative) controls completed follow up in the case-control study. Household air pollution was not associated with pneumonia in HIV-positive (e.g. ambulatory particulate matter adjusted odds ratio [aOR] 1.00 [95% CI 1.00-1.01, p=0.141]) or HIV-negative (e.g. aOR 1.00 [95% CI 0.99-1.01, p=0.872]) participants. Chronic respiratory disease was associated with pneumonia in HIV-positive (aOR 28.07 [95% CI 9.29-84.83, p < 0.001]) and HIV-negative (aOR 104.27 [95% CI 12.86-852.35, p < 0.001]) participants. Conclusions: There is insufficient evidence in the existing literature to confirm an association between household air pollution and pneumonia in adults. Previous studies have been limited by methodological issues. To address these challenges, this thesis has added to the growing body of literature regarding biomarkers of household air pollution exposure. However, our finding suggest that neither airway macrophage particulate load nor exhaled carbon monoxide are well suited for use at scale in resource poor settings. This thesis reports the largest study of household air pollution and adult pneumonia to date, with detailed exposure and outcome assessments. Although the case-control study sample size was not met, we found no evidence for an association between household air pollution and pneumonia in Malawian adults; further studies should be conducted to ensure that future public health resources are appropriately targeted. Broader solutions, including tackling poverty, malnutrition and chronic respiratory disease, will likely be required to reduce the burden of pneumonia in resource poor settings.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:755680 |
| Date | January 2018 |
| Creators | Jary, Hannah Rose |
| Contributors | Mortimer, Kevin ; Peterson, Ingrid ; Gordon, Stephen |
| Publisher | University of Liverpool |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://livrepository.liverpool.ac.uk/3021663/ |
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