Trial Methodology
The Household Air Pollution Intervention Network (HAPIN) was a randomized controlled trial of a liquefied petroleum gas (LPG) stove and fuel intervention in 3,200 households in four countries. HAPIN was launched in 2017, main enrollment started in 2018, and follow-up participation ended in 2021. The research team established trial sites in Guatemala, India, Peru, and Rwanda that each recruited 800 pregnant women, their 800 infants, and approximately 120 older adult women in the household into the study. Half of the participating households were randomly assigned to receive an LPG cookstove and fuel, and the other half served as controls using their customary cooking practices.
Participating households were followed for 18 months with extensive air monitoring of stove use and personal exposure to household air pollution, as well as extensive assessments of health outcomes. In children, health assessments included preterm birth, birth weight, growth, and respiratory infections. In adults, health assessments included respiratory function, blood pressure, inflammation, and other indicators of health disease.
Ongoing Work
Currently, the investigators are analyzing data for the primary outcomes. In children, the primary outcomes of interest are low birth weight, severe pneumonia incidence, and stunting, while abnormal blood pressure is the primary outcome of interest in older women. Secondary outcomes for children include preterm birth and childhood development. Secondary outcomes for pregnant women include abnormal maternal blood pressure during pregnancy, and for older adult women include impaired endothelial function, respiratory impairment, arteriosclerosis, carcinogenic metabolites, and reduced quality of life.
Research suggests that exposure experienced during gestation and early life is linked to a range of longer-term health outcomes, and that the benefits of reduced exposure will continue even if the intervention ends. Therefore, we submitted a proposal and received funding to continue to follow children at three of the research sites—Guatemala, India, and Rwanda—through age five to evaluate the effects of the original HAPIN intervention on neurologic and physical development.
The work builds on the major investment already made in the HAPIN trial by evaluating whether the benefits of the intervention extend beyond pregnancy and the child's first year of life. By leveraging a well-characterized cohort in three diverse settings, the work will provide rigorous and widely generalizable answers to questions important for both science and policy. We are maximizing potential for success by extending our prior research, using an experienced and proven research team with strong and ongoing relationships with participants. Visit the Extended Follow-up tab to learn more about our ongoing data collection.
For further information on the pre-specified outcomes of the trial, it is registered on ClinicalTrials.gov as NCT02944682. For a full description of the methods, overall study, biomarker, and exposure and stove use assessment protocol papers have all been published.
Multiple papers on study outcomes have been published, including exposure reduction and three of the four main outcomes: birth weight , stunting, and severe infant pneumonia. See the Publications tab for all of the HAPIN articles that have been published to-date.
Involved Parties
The HAPIN trial was funded by the National Institutes of Health (NIH) and the Bill & Melinda Gates Foundation. Participating NIH components included: the National Heart, Lung, and Blood Institute, the National Cancer Institute, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institute of Environmental Health Sciences, the NIH Common Fund of the NIH Office of the Director, and the Fogarty International Center. The Global LPG Partnership provided expert advice to the consortium.