Ambulatory monitoring demonstrates an acute association between cookstove-related carbon monoxide and blood pressure in a Ghanaian cohort

Abstract

Background: Repeated exposure to household air pollution may intermittently raise blood pressure (BP) and affect cardiovascular outcomes. We investigated whether hourly carbon monoxide (CO) exposures were associated with acute increases in ambulatory blood pressure (ABP); and secondarily, if switching to an improved cookstove was associated with BP changes. We also evaluated the feasibility of using 24-h ambulatory blood pressure monitoring (ABPM) in a cohort of pregnant women in Ghana.

Methods: Participants were 44 women enrolled in the Ghana Randomized Air Pollution and Health Study (GRAPHS). For 27 of the women, BP was measured using 24-h ABPM; home blood pressure monitoring (HBPM) was used to measure BP in the remaining 17 women. Personal CO exposure monitoring was conducted alongside the BP monitoring.

Results: ABPM revealed that peak CO exposure (defined as ≥4.1 ppm) in the 2 hours prior to BP measurement was associated with elevations in hourly systolic BP (4.3 mmHg [95% CI: 1.1, 7.4]) and diastolic BP (4.5 mmHg [95% CI: 1.9, 7.2]), as compared to BP following lower CO exposures. Women receiving improved cookstoves had lower post-intervention SBP (within-subject change in SBP of -2.1 mmHg [95% CI: -6.6, 2.4] as compared to control), though this result did not reach statistical significance. 98.1% of expected 24-h ABPM sessions were successfully completed, with 92.5% of them valid according to internationally defined criteria.

Conclusions: We demonstrate an association between acute exposure to carbon monoxide and transient increases in BP in a West African setting. ABPM shows promise as an outcome measure for assessing cardiovascular health benefits of cookstove interventions.

Trial registration: The GRAPHS trial was registered with clinicaltrials.gov on 13 April 2011 with the identifier NCT01335490 .

Keywords: Ambulatory blood pressure monitoring; Biomass; Blood pressure; Carbon monoxide; Cookstoves; Household air pollution.

Conflict of interest statement

Ethics approval and consent to participate

Ethical approvals for this study were obtained from the Institutional Review Board of Columbia University Medical Center and the Kintampo Health Research Centre Institutional Ethics Committee. Informed consent was obtained from all human subjects before the research began.

Consent for publication

Not applicable.

Competing interests

DS is a consultant for Abbott Vascular and Novartis Pharmaceuticals Corporation.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Flow chart of study activities

Fig. 2

Example data from 24-h ABPM and concurrent CO exposure monitoring session. Black dots and lines: SBP (mmHg). Blue dots and lines, DBP (mmHg). Green lines: minute-averaged CO (ppm). Grey hatching indicates the sleep period

Fig. 3

a 75th–95th percentiles of 2-h moving average of CO across 20 24-h personal monitoring sessions. b Beta coefficients for effect of CO exposure above 75th–95th percentile thresholds on hourly SBP, with thresholds determined using the distribution of CO exposure across all 20 monitoring sessions, N indicates the number of monitoring sessions included in the model for each percentile. c as b, but for DBP

Fig. 4

Beta coefficients for effect of CO exposure on above 75th–95th percentile thresholds on hourly BP, with thresholds determined within each monitoring session (N = 20 for all percentiles, indicating all data was included in each model). Multilevel regression models were adjusted for awake time and morning period, with 24-h ABPM monitoring session as the grouping variable. Error bars indicate the 95% CI for the beta coefficient. a SBP; b DBP

Fig. 5

Boxplots of mean 72-h personally-monitored CO before and after a stove intervention. Dark lines indicate median values before and after the intervention. Only the group receiving the LPG stove intervention demonstrates a significant post-intervention reduction in CO

Fig. 6

SBP/DBP change (Session 2 – Session 1) by intervention status. Negative values indicate session 2 (post-intervention) BP was lower than session 1 BP; positive values indicate the reverse