Indoor Air Pollution And Cardiovascular Disease: An Echo Study In A Rural Village In Nepal

Background: Biomass fuels (BMF) are widely used in developing countries for cooking and heating and thus represent an important cause of indoor air pollution (IAP). While outdoor is pollution is an established cause of cardiovascular (CV) morbidity and mortality, the role of IAP is less studied. Aims: The aim of this study was to investigate whether exposure to IAP due to BMF combustion is associated with subclinical cardiovascular damage in individuals living in the rural village of Chaurikharka, Nepal. Methods: 72 subjects, belonging to Sherpa ethnicity, without established CV diseases were enrolled. Cardiac ultrasound , flow mediated dilation (FMD) and glyceryl trinitrate (GTN) mediated dilation of the brachial artery, carotid geometry and stiffness and aortic pulse wave velocity (PWV) were performed in all subjects. Ventilation features of the buildings were studied. Carbon monoxide (CO) and black carbon (BC) levels in the inhabitation were measured in 9 houses. Results: In the study population all subjects used BMF as a primary energy source. 33% had chimneys (CH) while 67% had no chimneys (NCH). In the houses without chimneys CO ambient concentration was significantly increased [CO amb. NCH: 26(11-93) vs. CH 3(3-3) ppm; p=0.04] whereas BC was found to be increased even though not significantly. The prevalence of hypertension, diabetes and hypercholesterolemia were not significantly different in 2 groups. Blood pressure and heart rate were comparable while oxygen saturation SO2 tended to be higher in NCH group. Baseline shear rate tended to be higher in the CH group (194 ± 103 vs 154 ± 66 s-1; p=0.07) and after correcting for age, sex and SO2 the difference became significant. FMD was reduced but not significantly in the NCH group (FMD% 3.92 ± 2.16 vs 4.54 ± 2.67; p=0.30) while GTN% was similar in the two groups. Carotid intima-media thickness (C-IMT) was significantly increased in the NCH group (C-IMT: 0.580 ± 0149 vs 0.499 ± 0.08 mm; p=0.01). Even after adjustment for age, sex and SO2 C-IMT tended to be increased in the NCH group (p=0.08). No significant difference in carotid stiffness and PWV was found. In the NCH group left ventricle end-diastolic volume (LVEDV) was significantly reduced (LVEDV: 70.8 ± 24.9 vs 77.0 ± 15.7 ml; p=0.04) while left ventricle end-systolic volume (LVESV) tended to inferior (LVTSV: 25.1 ± 11.8 vs 27.1 ± 8.6 ml; p=0.15). Ejection fraction was comparable. Moreover in the NCH group, stroke volume (SV) was significantly reduced (SV: NCH 62.5 ± 16.1 vs. CH 69.5 ± 13.5 ml; p=0.05) and cardiac output (COu) tended to be inferior (COu: NCH 4.2 ± 1.0 vs CH 4.7 ± 1.1 l/min; p=0.07). In the linear correlation, SV tended to be inversely correlated with CO amb. ON (r=-0.24; p=0.14). Right ventricle-right atrium gradient (RV-RA gradient) tended to be higher in the NCH group (22.2 ± 4.9 vs 20.3 ± 4.3 mmHg, p=0.11), while in the linear regression, RV-RA gradient was significantly correlated with BC average concentration in the houses (r=0.46; p=0.03; n=21). Conclusions: In rural Nepalese high-altitude dwellers using BMF, increased levels of IAP due to the absence of chimney is associated with reduced baseline shear rate, increased C-IMT and reduced stroke volume. This study suggests that simple interventions to improve indoor air quality, such as providing chimneys may reduce the CV risk related to exposure to IAP