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Household air pollution from burning solid fuels is responsible for an estimated 2.9 million premature deaths worldwide each year and 4.5% of global disability-adjusted life years, while cooking and fuel collection pose a considerable time burden, particularly for women and children. Cleaner burning biomass-fuelled cookstoves have the potential to lower exposure to household air pollution as well as reduce fuelwood demand by increasing the combustion efficiency of cooking fires, which may in turn yield ancillary benefits in other domains. The present paper capitalises on opportunities offered by the Cooking and Pneumonia Study (CAPS), the largest randomised trial of biomass-fuelled cookstoves on health outcomes conducted to date, the design of which allows for the evaluation of additional outcomes at scale. This mixed methods study assesses the impact of cookstoves on primary school absenteeism in Karonga district, northern Malawi, in particular by conferring health and time and resource gains on young people aged 5–18. The analysis combines quantitative data from 6168 primary school students with in-depth interviews and focus group discussions carried out among 48 students in the same catchment area in 2016. Negative binomial regression models find no evidence that the cookstoves affected primary school absenteeism overall [IRR 0.92 (0.71–1.18), p = 0.51]. Qualitative analysis suggests that the cookstoves did not sufficiently improve household health to influence school attendance, while the time and resource burdens associated with cooking activities—although reduced in intervention households—were considered to be compatible with school attendance in both trial arms. More research is needed to assess whether the cookstoves influenced educational outcomes not captured by the attendance measure available, such as timely arrival to school or hours spent on homework.
Data collection associated with the Cooking and Pneumonia Study was reviewed and approved by the Malawi College of Medicine Research and Ethics Committee (P.11/12/1308) and the Liverpool School of Tropical Medicine Research Ethics Committee (Ref #12.40). Data collection associated with the Karonga Health and Demographic Surveillance System was reviewed and approved by the National Health Sciences Research Committee (NHSRC) in Malawi (Protocol #419) and the London School of Hygiene and Tropical Medicine (LSHTM) Research Ethics Committee (Ref #5081). Data collection associated with the nested qualitative study was reviewed and approved by the NHSRC in Malawi (Protocol #15/11/1509) and the LSHTM Research Ethics Committee (Ref #10401). The Cooking and Pneumonia Study, implemented from July 2014-September 2016, involved one hundred community-level clusters in Karonga district, northern Malawi, randomised to intervention or control groups. An additional 50 clusters were enrolled in a second site in southern Malawi, but these are not the focus of the present study. A full description of the trial design and randomisation procedures is available in Mortimer et al. [20]. Within intervention clusters, eligible households received two Philips HD4012LS cookstoves with cooking pots and a solar panel with which to charge the in-built battery-powered fan, as well as user training. As the trial’s primary outcome of interest was incidence of pneumonia in children under five years old [20], cookstoves were distributed only to households with children below 4.5 years at baseline, as well as on a continuous basis to eligible in-migrating households or those into which children under five were born, adopted or fostered over the course of the two-year follow-up period. The CAPS team visited households approximately every three months to collect information about cookstove usage and functionality. A free repair, maintenance and replacement service was provided for damaged cookstoves and solar panels. Control households received their own cookstoves at the end of the trial. To examine the impact of cookstoves on primary school attendance, we identified young people of primary school age resident in households enrolled in the CAPS trial. Primary school in Malawi comprises eight grades but, in light of the frequency of late entry and grade repetition among Malawian students [21], we included children aged 5–18. The total number of absence days in the past four weeks that school was in session was collected as part of the annual household survey of the Karonga Health and Demographic Surveillance System [22], which formed the catchment area of the CAPS trial. School attendance reports were drawn from the first HDSS interview that took place at least 60 days after the household was enrolled in CAPS. A threshold of 60 days was chosen to allow for a short cookstove adjustment period—for instance, to deplete existing stocks of firewood—and in light of the HDSS survey design in which absenteeism over the past four weeks was retrospectively reported. Schooling information was provided by household members aged 15 years or older who were at home at the time of the field team’s visit; as such, most respondents were parents or other adult relatives reporting on behalf of resident children. The primary analysis followed intention-to-treat (ITT) principles, where the ITT population consisted of primary school students aged 5–18 living in CAPS intervention or control households at the time of enrolment, and who had at least one follow-up CAPS and HDSS survey. A per-protocol analysis was also conducted for comparison, excluding students who changed cookstove exposure status between CAPS enrolment and the first eligible HDSS survey by: 1) moving from an intervention household to a new household in a control cluster, 2) moving from a control household to a new intervention household, or 3) moving from a cookstove to a non-cookstove household within an intervention cluster. It also excluded students living in households that reported not using the cookstove exclusively in the CAPS visit closest to the HDSS schooling interview—that is, households that did not use the cookstove as a result of breakage, mechanical failure, or personal preference, or that continued to use open fire cooking methods alongside the cookstove for at least some household meals. Finally, the per-protocol analysis excluded students from households for whom data from a CAPS follow-up visit were not available within three months of the HDSS survey. Negative binomial regression modelling was used to compare absenteeism across trial groups to reflect overdispersion in the distribution of absence days. Given the high proportion of non-absence in the study population, zero-inflated negative binomial regression models were also estimated but were found neither to perform better than, nor to change the conclusions of, standard negative binomial models. All regression models included cluster robust standard errors to account for the clustered trial design. Multivariable models adjusted for the following pre-specified covariates, informed by the analyses presented in Mortimer et al. [20]: age, sex, current grade attended, repetition of current grade, maternal death, paternal death, maternal education, paternal education, total number of household members, number of younger household members, relationship to household head, sex of household head, household socioeconomic status, co-residence with a regular smoker, and exposure to sources of household smoke other than cooking. Socioeconomic status was constructed by using principal components analysis [23, 24] to generate a wealth index combining ownership of ten durable goods, two variables indicating a shortage of food or bathing soap in the past year, and two variables indicating a household’s access to an improved water source or improved toilet facility. A variable indicating the HDSS survey round was also included in regression models to control for survey-specific differences in absenteeism reporting, as was the month of interview to account for seasonal differences in absenteeism. A further variable indicating whether HDSS survey took place during term time or school holiday was additionally included, alongside a variable specifying the number of months between CAPS enrolment and the HDSS survey to adjust for potential changes in cookstove usage over time. By adding appropriate interaction terms to each regression model, subgroup analyses were also conducted to investigate the following secondary hypotheses: To corroborate the quantitative comparisons and elucidate the proposed mechanisms at play [26], a nested qualitative study was conducted in April-May 2016 among male and female primary school students aged 12–18, involving 16 in-depth interviews (IDIs) and four focus group discussions (FGDs) with eight participants per group. The qualitative sample was purposively selected using the HDSS and CAPS datasets to ensure distribution across trial arms, variation by age and school grade attended, as well as representation from the three community types present in the study area: lakeshore, roadside, and rural agricultural. Interviews and FGDs solicited students’ perceptions of the barriers to regular school attendance, household and community support for schooling, intra-household allocation of domestic responsibilities and household health status. As the basis for follow-up discussion about students’ time use, IDIs additionally included an exercise whereby participants were asked to fill a timeline with the activities in which they had engaged on the previous school day, choosing from a selection of ten illustrated activity cards: attending school, doing homework, going to the market, collecting firewood, drawing water, cooking, fishing, farming, caregiving, and playing. Among cookstove recipients, IDIs also explored the perceived impact of cleaner burning cookstoves on health, schooling and time allocation. In-depth interview and FGD topic guides were iteratively updated to reflect emerging themes from a pilot phase and from preliminary data analysis. Qualitative activities were conducted by a team of four trained interviewers/facilitators in the participants’ local language, Chitumbuka, and subsequently transcribed and translated into English by the same research team. As a validity check, four IDI transcripts—one per interviewer—were externally audited for completeness and accuracy by a bilingual consultant. Since errors identified during this process were minimal and minor, no additional review of the remaining transcripts was undertaken. The final transcripts were uploaded into NVivo software for coding and thematic analysis [27], with particular focus on aspects of students’ narratives that supported, challenged or undermined the pathways linking cookstoves and school attendance shown in Fig 1.
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