Effect of Liquefied Petroleum Gas Stove and Fuel Intervention During Gestation and Infancy on Height-for-age Z score and Stunting at Ages 2 to 5: an analysis from the multi-country Household Air Pollution Intervention Network trial. Restricted; Files Only
Kalam, Md Abul (Summer 2026)
Abstract
Linear growth faltering (stunting) is a major global public health challenge in low- and middle-income countries (LMICs). A substantial body of evidence from birth cohort studies shows that growth faltering typically begins in utero and rises steeply during the first two years of life. However, very few cohort studies have examined patterns of growth faltering beyond this period. Similarly, predictors of stunting—spanning biological, nutritional, socio-economic, and environmental factors—are often framed as age-specific, with early life shaped by maternal and birth conditions and later childhood by broader living conditions. However, this interpretation largely reflects cross-sectional evidence and may obscure the persistent influence of early-life factors. Longitudinal studies help overcome this limitation; however, most are restricted to the first two years of life, leaving it unclear whether early-life exposures independently predict later stunting, particularly during the next 1000 days.
A growing body of literature links household air pollution (HAP) to stunted growth in LMICs. Prenatal exposure to pollutants such as particulate matter (PM2.5), carbon monoxide (CO), and black carbon (BC) can impair fetal growth through oxidative stress, inflammation, and epigenetic changes. Postnatally, infants and young children remain highly exposed to HAP within household environments, potentially increasing their risk of stunting. Interventions promoting clean cookstoves and fuels have aimed to reduce this risk during critical growth periods; however, evidence shows no reduction in infant stunting at age 1. However, little is known about the longer-term benefits of such interventions at ages 2–5 years. Moreover, most studies rely on self-reported exposure (e.g., solid fuel use) or indirect measures (e.g., satellite-based estimates), which fail to capture pollutant-specific effects and individual-level variability. The lack of quantitative pollutant measurements limits specificity and comparability. Furthermore, current evidence provides limited insight into sensitive exposure windows, particularly during ages 2–5 years—a critical period for late-onset stunting and potential catch-up growth.
This dissertation uses data from the multi-country Household Air Pollution Network study, a randomized controlled trial designed to assess health effects from a liquefied petroleum gas (LPG) stove and fuel intervention randomized into a population of pregnant women in households that otherwise cook using solid biomass fuels. While the trial was completed after the children born into the study reached 12 months of age, HAPIN investigators continued to follow these children until age 5 years.
The overarching goal of this dissertation was to investigate the predictors of HAZ and stunting within the HAPIN study population and to determine the effects of the HAPIN intervention on post-trial height-for-age z score (HAZ) and stunting between ages 2 and 5 in Guatemala, India and Rwanda. It also explored the relationship between personal exposure to gestational and infancy [birth to 12 months of age] PM2.5, BC, and CO on HAZ and stunting during this period.
Aim 1 explored the trends and predictors of HAZ and stunting among children aged 2–5 years. Results showed that between ages 2 and 5 years, mean HAZ increased modestly across all three countries, although Guatemala consistently exhibited the lowest HAZ despite some improvement over time. Female children had slightly higher mean HAZ than males across follow-up visits. Early-life biological factors—including low birthweight, shorter maternal stature, and younger age—remained significant predictors of HAZ during ages 2–5, demonstrating the persistence of early-life vulnerabilities and their sustained influence on growth in pre-school years.
Aim 2 determined the effects of the HAPIN intervention on HAZ and stunting between ages 2 and 5 years. The results showed that the intervention with liquified petroleum gas cookstove with clean fuel delivered at gestation and infancy substantially reduced exposures to PM2.5, BC and CO in the intervention group. However, in the intention-to-treat analysis, we found no statistically significant effect of the intervention on either repeated measures of HAZ nor annual HAZ, stunting or severe stunting at any age. These findings extend prior evidence of no impact on growth through 12 months, indicating that early-life reductions in household air pollution did not translate into improved HAZ during the subsequent 1000 days.
Aim 3 examined the exposure–response relationships for personal exposure to PM2.5, CO, and BC and HAZ through 2 to 5 years of age. The adjusted mixed-effects model showed that a log unit increase in gestational exposure to PM2.5 was associated with a -0.06 SD change in HAZ. Quartile model showed that, compared with the lowest exposure quartile, higher gestational PM2.5 exposure was associated with lower HAZ scores in the second, third, and fourth quartiles. These associations were mainly driven by child birthweight as found in the interaction term analysis. No association was found between gestation exposures to CO and BC with HAZ. There was no significant association between HAZ and infancy exposure to PM2.5, CO, and BC. Although the HAPIN intervention substantially lowered exposures, reductions during pregnancy may have been too late to offset earlier exposure effects. Hence, interventions should target preconception and early pregnancy periods to yield benefits on HAZ.
This dissertation highlights the critical role of timing in shaping child growth, demonstrating that early-life biological and environmental exposures persist in influencing growth into later childhood. Despite substantial reductions in air pollution exposures, the LPG intervention did not improve growth or reduce stunting risk from ages 2 through 5 years. The exposure-response analysis showed that gestational exposure to PM2.5 is associated with decreased HAZ. Future efforts should prioritize earlier interventions, especially during preconception and early pregnancy, to effectively improve child growth outcomes.
Table of Contents
Chapter 1: Sub-optimal growth, stunting and household air pullulation. ................................ 1
Growth faltering or stunting is a global public health problem ............................................................. 1
Risk factors of linear growth faltering and stunting ................................................................................. 3
Air pollution and growth faltering or stunting .......................................................................................... 5
Aims and scope of this dissertation ............................................................................................................ 9
Chapter 2: Trends and predictors of height-for-age z-scores and stunting among children aged 2–5 years: an analysis from Household Air Pollution Intervention Network birth cohort in Guatemala, India and Rwanda. ........................................................................................... 18
Abstract ......................................................................................................................................................... 18
Introduction ................................................................................................................................................. 20
Materials and methods ................................................................................................................................ 23
Study design and setting ......................................................................................................................... 23
Study population ..................................................................................................................................... 23
Outcome variables .................................................................................................................................. 24
Independent variables ............................................................................................................................ 24
Modeling approach ................................................................................................................................. 27
Statistical analysis .................................................................................................................................... 29
Results ........................................................................................................................................................... 31
Analytic sample ....................................................................................................................................... 31
Study population characteristics ........................................................................................................... 32
Trend and distribution of height-for-age z scores and prevalence of stunting ............................. 35
Predictors of Height-for-age Z scores and stunting .......................................................................... 36
Country specific predictors of HAZ and stunting ............................................................................. 38
Discussion .................................................................................................................................................... 41
Strengths and limitations ............................................................................................................................ 44
Recommendations ....................................................................................................................................... 46
Conclusions .................................................................................................................................................. 46
Supplementary files ..................................................................................................................................... 50
Chapter 3: Effects of a 500-day LPG cookstove and fuel intervention delivered during gestation and infancy on height-for-age (HAZ) and stunting at ages 2, 3, 4 and 5 years: findings from the multi-country HAPIN trial. ........................................................................ 73
Abstract ......................................................................................................................................................... 73
Introduction ................................................................................................................................................. 75
Materials and methods ................................................................................................................................ 76
Study design and participants ................................................................................................................ 76
Outcome measurement .......................................................................................................................... 78
Exposure measurement ......................................................................................................................... 78
Statistical analyses ................................................................................................................................... 79
Height for age z scores (HAZ). ............................................................................................................ 79
Annual stunting and severe stunting .................................................................................................... 80
Ethics review and trial registration statement ..................................................................................... 82
Results ........................................................................................................................................................... 82
Participants .............................................................................................................................................. 82
Baseline characteristics ........................................................................................................................... 83
Child characteristics ................................................................................................................................ 85
Exposure to air pollutants ..................................................................................................................... 85
Effect of the intervention on primary and secondary outcomes ..................................................... 86
Intervention effects on height-for-age z-scores (HAZ) repeated measures from ages 2 to 5 years .......................................................................................................................................................... 87
Discussion .................................................................................................................................................... 91
Conclusion .................................................................................................................................................... 94
Supplementary files ..................................................................................................................................... 96
Chapter 4: Exposure–response relationships for personal exposure to fine particulate matter (PM2.5), carbon monoxide, and black carbon and height for age Z scores through 2 to 5 years of age: an analysis from the multi-country Household Air Pollution Intervention Network (HAPIN) trial ........................................................................................................................ 107
Abstract ...................................................................................................................................................... 107
Introduction .............................................................................................................................................. 109
Methods ..................................................................................................................................................... 111
Study participants and settings ........................................................................................................... 111
Personal exposure monitoring ........................................................................................................... 112
Outcomes measurements ................................................................................................................... 113
Covariates .............................................................................................................................................. 114
Statistical analysis ................................................................................................................................. 114
Ethical considerations ......................................................................................................................... 116
Results ........................................................................................................................................................ 116
Participants ........................................................................................................................................... 116
Maternal, child and household characteristics ................................................................................. 117
Exposure and outcomes ..................................................................................................................... 120
Exposure-response analysis with gestational exposures and HAZ between ages 2-5 years ..... 122
Effect modification on gestational exposures and HAZ ............................................................... 124
Exposure-response analysis with infancy exposures and HAZ between ages 2-5 years ........... 125
Effect modification on infancy exposures and HAZ ..................................................................... 126
Discussion ................................................................................................................................................. 128
Conclusion ................................................................................................................................................. 131
Supplementary files .................................................................................................................................. 133
Chapter 5: Discussion and conclusion ................................................................................... 151
Introduction .............................................................................................................................................. 151
Summary of dissertation research .......................................................................................................... 154
Conclusions ............................................................................................................................................... 156
Interpretation and reflections ................................................................................................................. 158
Limitations ................................................................................................................................................. 163
Recommendations and future research directions .............................................................................. 165
References ................................................................................................................................................. 170
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