Studies of Household Air Pollution and Subclinical Indicators of Cardiovascular Disease Fill Important Knowledge Gaps.

Abstract

In their article “Targeting Household Air Pollution for Curbing the Cardiovascular Disease Burden: A Health Priority in Sub-Saharan Africa,” Noubiap and colleagues review the literature on household air pollution (HAP) and cardiovascular diseases.1 They point to the lack of studies on cardiovascular events in sub-Saharan Africa and other regions where cooking and heating with solid fuels is common. They also review studies of exposure to cigarette smoke and urban air pollution (mostly in high-income countries) and associated cardiovascular endpoints, including studies of intermediary indicators of cardiovascular risk such as inflammation, endothelial dysfunction, and heart rate variability. This evidence base contributes to both our knowledge of biological mechanisms linking air pollution and cardiovascular outcomes and appropriate indicators of cardiovascular risk. Linking evidence from urban air pollution and HAP, as the authors suggest, assumes that they are equally harmful to human health. Therefore, what is surprisingly absent from their review is the increasing body of evidence linking HAP with important subclinical indicators of cardiovascular diseases, including blood pressure, which is strongly and directly related to cardiovascular mortality.2 For example, a previous study in rural China found a dose-response relationship between personal exposure to HAP and blood pressure in women cooking with biomass fuels,3 and several cookstove intervention studies in Latin America found lowered blood pressure4-7 and reduced ST-segment depression8 in women with reduced exposure to HAP. Cross-sectional studies in Peru found higher blood pressure and greater prevalence of carotid atherosclerotic plaque among biomass users compared with users of gaseous fuels9, 10 and a small feasibility study in China found some evidence of an association between exposure to biomass smoke and arterial stiffness.11 Controlled evaluations conducted in high-income countries provide further evidence; short-term changes in exposure to woodsmoke were associated with arterial stiffness in a laboratory-based study of healthy Swedish adults12, 13 and an air filtration intervention resulted in improved markers of systemic inflammation and endothelial function (but not oxidative stress) among Canadian adults living in a woodsmoke-impacted community.14 We applaud Noubiap and colleagues for highlighting this important and often underrepresented global health issue to the readership of The Journal of Clinical Hypertension. We particularly appreciate the focus on energy and air pollution in sub-Saharan Africa, where much of the population is heavily impacted by exposure to HAP and its associated disease burden.15 We do, however, feel inclined to draw attention to the important omission of the growing body of research evaluating the association between HAP with these important indicators of cardiovascular disease risk. While it is our hope that this research base should be used to inform future evaluations in all regions of the world, it is certainly worth noting that few studies have been conducted in sub-Saharan Africa. Obtaining direct evidence in this region will have important public health implications and should be heavily prioritized. The authors do not have any conflicts of interest to declare.