Study protocol for a stepped-wedge randomized cookstove intervention in rural Honduras: household air pollution and cardiometabolic health

Abstract

Background: Growing evidence links household air pollution exposure from biomass-burning cookstoves to cardiometabolic disease risk. Few randomized controlled interventions of cookstoves (biomass or otherwise) have quantitatively characterized changes in exposure and indicators of cardiometabolic health, a growing and understudied burden in low- and middle-income countries (LMICs). Ideally, the solution is to transition households to clean cooking, such as with electric or liquefied petroleum gas stoves; however, those unable to afford or to access these options will continue to burn biomass for the foreseeable future. Wood-burning cookstove designs such as the Justa (incorporating an engineered combustion zone and chimney) have the potential to substantially reduce air pollution exposures. Previous cookstove intervention studies have been limited by stove types that did not substantially reduce exposures and/or by low cookstove adoption and sustained use, and few studies have incorporated community-engaged approaches to enhance the intervention.

Methods/design: We conducted an individual-level, stepped-wedge randomized controlled trial with the Justa cookstove intervention in rural Honduras. We enrolled 230 female primary cooks who were not pregnant, non-smoking, aged 24-59 years old, and used traditional wood-burning cookstoves at baseline. A community advisory board guided survey development and communication with participants, including recruitment and retention strategies. Over a 3-year study period, participants completed 6 study visits approximately 6 months apart. Half of the women received the Justa after visit 2 and half after visit 4. At each visit, we measured 24-h gravimetric personal and kitchen fine particulate matter (PM_2.5) concentrations, qualitative and quantitative cookstove use and adoption metrics, and indicators of cardiometabolic health. The primary health endpoints were blood pressure, C-reactive protein, and glycated hemoglobin. Overall study goals are to explore barriers and enablers of new cookstove adoption and sustained use, compare health endpoints by assigned cookstove type, and explore the exposure-response associations between PM_2.5 and indicators of cardiometabolic health.

Discussion: This trial, utilizing an economically feasible, community-vetted cookstove and evaluating endpoints relevant for the major causes of morbidity and mortality in LMICs, will provide critical information for household air pollution stakeholders globally.

Trial registration: ClinicalTrials.gov Identifier NCT02658383 , posted January 18, 2016, field work completed May 2018. Official title, "Community-Based Participatory Research: A Tool to Advance Cookstove Interventions." Principal Investigator Maggie L. Clark, Ph.D. Last update posted July 12, 2018.

Keywords: Biomass fuel; Blood pressure; C-reactive protein; Cardiovascular health; Hemoglobin A1c; Household air pollution; Metabolic health; Particulate matter; Personal exposure; Randomized controlled trial.

Fig. 1

Examples of a primary traditional cookstove (a) and secondary traditional cookstove (b), and internal and external views of Justa cookstoves (c, d)

Fig. 2

Examples of exposure collections: post-sampling filter (a), kitchen exposure monitors near cookstove (b), and personal UPAS monitor (c). Photo credits: Joanna B. Pinneo (a)

Fig. 3

Examples of collection for the primary health endpoints: blood pressure (a), dried blood spots C-reactive protein (b), and finger-stick sample for glycated hemoglobin (HbA1c) (c). Photo credits: Joanna B. Pinneo (b)

Fig. 4

Examples of SUMs on the chimney of a primary traditional cookstove (a) and a secondary traditional cookstove (b), circled in red