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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 7  |  Issue : 4  |  Page : 192-195

Noncommunicable diseases associated with household air pollution from biomass fuel in South-East Asia region: A systematic review and meta-analysis protocol


1 Centre of Excellence for Evidence Based Research on NCDs in LMICs, World NCD Federation, Chandigarh, India
2 Department of Pharmacology, Post Graduate Institute of Medical Education and Research, Chandigarh, India
3 Department of Community Medicine, School of Public Health, Post Graduate Institute of Medical Education and Research, Chandigarh, India

Date of Submission27-Sep-2022
Date of Decision30-Nov-2022
Date of Acceptance01-Dec-2022
Date of Web Publication07-Jan-2023

Correspondence Address:
J S Thakur
Department of Community Medicine, School of Public Health, Post Graduate Institute of Medical Education and Research, Chandigarh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jncd.jncd_69_22

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  Abstract 


Introduction: The WHO states that around 2.6 billion people still cook using solid fuels (such as wood, crop wastes, charcoal, coal, and dung) and kerosene in open fires and inefficient stoves. Evidence suggests that exposure to indoor air pollution by biomass fuel cooking is associated with chronic obstructive pulmonary disease, asthma, cardiovascular diseases, lung cancer, hypertension, depression, breast cancer, and cataract. This systematic review aims at providing evidence-based insight into indoor air pollution by comprehensively assessing the association of major noncommunicable diseases with the household air pollution from biomass solid fuel.
Methods and Analysis: We will undertake a systematic search in PubMed, EMBASE, Scopus, OVID, MEDLINE, and Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library from January 2000 to April 2022. The study designs to be included will be cross-sectional, case-control, cohort, and randomized controlled trials. Subgroup analyses will be performed, and sensitivity analyses will be conducted to assess the robustness of the findings.
Ethics and Dissemination: No ethical issues are foreseen. Dissemination will be done by submitting scientific articles to academic peer-reviewed journals. We will present the results at relevant conferences and meetings.
Study Design: Systematic review and meta-analysis.
Conclusion: This systematic review will collate empirical evidence to assess the association of NCDs with the household air pollution from biomass fuel.
Prospero Registration: CRD42022356857.

Keywords: Biomass fuel, household air pollution, indoor air pollution, noncommunicable diseases, South-East Asia Region


How to cite this article:
Rana A, Kaur R, Malhotra S, Thakur J S. Noncommunicable diseases associated with household air pollution from biomass fuel in South-East Asia region: A systematic review and meta-analysis protocol. Int J Non-Commun Dis 2022;7:192-5

How to cite this URL:
Rana A, Kaur R, Malhotra S, Thakur J S. Noncommunicable diseases associated with household air pollution from biomass fuel in South-East Asia region: A systematic review and meta-analysis protocol. Int J Non-Commun Dis [serial online] 2022 [cited 2023 Feb 1];7:192-5. Available from: https://www.ijncd.org/text.asp?2022/7/4/192/367306




  Introduction Top


The WHO states that around 2.6 billion people still cook using solid fuels (such as wood, crop wastes, charcoal, coal, and dung) and kerosene in open fires and inefficient stoves.[1] Incomplete combustion causes fine particulate particles to be released into the air, filling the kitchen with smoke containing particulate matter, methane, carbon monoxide, polyaromatic hydrocarbons, and volatile organic compounds. The vast majority of this population (1.9 billion) are from developing countries of Asia.[2] The International Agency for Research on Cancer classified Household Air Pollution (HAP) from the coal as a known human carcinogen (IARC Group 1), while HAP from biomass was classed as a potential human carcinogen (IARC Group 2A).[3]

Evidence suggests that exposure to indoor air pollution by biomass fuel cooking is associated with chronic obstructive pulmonary disease (COPD), cardiovascular diseases (CVDs), hypertension, and lung cancer.[4],[5],[6],[7],[8],[9] The long-term solid fuel combustion for cooking may increase the risk of breast cancer.[10] Various studies have reported harmful effects of indoor air pollution but there is no systematic review which comprehensively provides the evidence about occurrence of noncommunicable diseases (NCDs) from biomass fuel combustion.

This systematic review aims at providing evidence-based insight into indoor air pollution by comprehensively assessing the association of major noncommunicable diseases with the HAP from biomass solid fuel.


  Methods Top


In reporting the protocol for this review, Preferred Reporting Items for Systematic reviews and Meta-Analyses Protocols checklist have been adhered to and will be provided as a supplementary file along with the main manuscript.

Population

We will include studies examining the general population of all age groups. The populations of interest will be the individuals exposed to indoor air pollution from household fuel combustion.

Intervention/Exposure

Exposure to indoor/HAP from the biomass fuel.

Comparator

Individuals who use cleaner household fuels or not exposed to polluting household fuel combustion.

Outcome

To derive risk estimates of NCDs associated with HAP from biomass fuel combustion which are CVDs, ischemic heart diseases, stroke, COPD, asthma, cancers (lung cancer, oral cancer, breast cancer, cervical cancer, liver cancer, colorectal cancer, and esophageal cancer), diabetes mellitus, chronic kidney disease (CKDs), depression, hypertension, and cataract.

Inclusion and exclusion criteria

Inclusion criteria

All the cross-sectional, case − control studies and cohort studies will be included. There will be no age restrictions and only English language publications will be included. We will include studies reporting risk of NCDs including CVD, ischemic heart disease, stroke, asthma, COPD, cancers (lung cancer, oral cancer, breast cancer, cervical cancer, liver cancer, colorectal cancer, and esophageal cancer), diabetes mellitus, CKD, depression, hypertension, and cataract in people exposed to HAP. Studies evaluating outdoor air pollution, people exposed to active or passive smoking will not be considered. Studies reporting Risk ratio (RRs) for the outcomes of indoor pollutant concentrations, risk in those exposed to gas cooking or heating compared with those unexposed were included. Initially, the selected research studies will be reviewed based on their titles and abstracts. In case of conflict, the third author will be consulted and decision to include or exclude study will be based on consensus. After study selection, the full texts will be acquired and reviewed. In case of unavailability of full text, the particular study will be omitted from the review with clear mention in the review document. Reviews, case reports, meeting abstracts, notes, letters, comments, and editorials with insufficient quantitative data required for the analysis (no risk estimate and no confidence intervals) and those overlapping with studies which are already considered will be excluded.

Search methods for identifying studies

For this systematic review and meta-analysis, we will do a systematic search of PubMed, Embase, MEDLINE, and Web of Science for studies evaluating the association between exposure to HAP and major NCDs. We will include all studies of any design published from January, 2000 to April, 2022. We will identify further studies through searches of bibliographies and references. We will include studies reporting risk of CVD, ischemic heart disease, stroke, asthma, COPD cancers (lung cancer, oral cancer, breast cancer, cervical cancer, liver cancer, colorectal cancer, and esophageal cancer), diabetes mellitus, CKD, depression, hypertension, and cataract in people exposed to HAP. Studies reporting relative risks (RRs) for the outcomes of indoor pollutant concentrations, risk in those exposed to gas cooking or heating compared with those unexposed were included.

Selection of trials and data abstraction

Two researchers (AR, RK) will screen the titles and abstracts individually and in a manner independent of each other to identify their relevancy. Titles and the abstracts of articles identified using searches will be imported to Rayyan. All of the duplicates discovered in the process will be removed. In addition to assessment of every abstract and title by both researchers, the supervisor (JST/SM) will further independently assess 50% of the abstracts. Retrieval of full-text articles will be done for articles for which the selection criteria is met or declared unclear by both reviewers. If both reviewers agree to the situation of even one selection criteria not being met then full-text retrieval will not be done. For the titles/abstracts, where all selection criteria found categorized as “no” by one reviewer were categorized entirely opposite or unclear by other reviewer, the final decision will be to retrieve the full text of the article for better review of selection criteria and if any disagreements are found during both stages then they will be resolved by discussion with third reviewer (JST/SM). Studies with a control group, studies with a sample size <30 and studies without a clearly defined intervention will be excluded. Multiple publications of the same study will be identified, grouped together and represented by a single reference.

Data extraction and management

Data will be extracted using data abstraction form which will be developed on Microsoft Excel 2010. The data abstraction tool will be piloted on a random sample of 5 trials and modified as per the feedback from team. Data will be extracted by one reviewer (AR) and checked against the original paper by a second independent reviewer (RK). Any disagreements during the process will be subject to discussion to reach a solution and if not resolved by discussion between the two then the issue will be resolved as per the final decision of the third reviewer (SM/JST). We will extract information on author, publication year, study design, study setting, study population, participant demographics, exposure and outcome evaluated and information for risk of bias assessment. Data extraction will be carried out independently by two investigators and conflicts will be adjudicated by a third. We will contact authors for additional data or clarification where required.

Quality of risk of bias assessment in included studies

Risk of bias assessment will be done using the New Castle-Ottawa scale (NOS). The NOS scale assesses three specific domains for each study depending on its design: selection of participants, comparability, and outcome ascertainment. Two authors will undertake assessment of risk bias (AR, RK) and arbitration will be done by a third author in case of disagreements (RK, JS, SM).

Data synthesis and analysis

We will extract RRs, 2 × 2 contingency tables, baseline characteristics of the study population, type of fuel or cook stove used in the exposed and comparator group, and detailed characteristics of the study design. In brief, RR meta-estimates for risk–outcome pairs will be computed using a random effects model. Heterogeneity will be assessed using the I2 statistic. Age and sex interactions will be evaluated for the risk of NCDs associated with HAP. The meta-analysis will be performed to calculate the pooled risk ratio (RR). The articles where the risk estimates and confidence intervals were reported within the articles, we will not calculate the confidence intervals but will instead use those reported within the article. However, the articles where risk ratio is not reported, a 2 × 2 contingency table will be extracted to calculate risk ratios and confidence intervals.

Statistical analysis will be performed using inverse variance method. This will include the natural logarithm (ln) transformation of the risk estimate, calculation of standard error from log transformation of difference between the upper and lower limits of the confidence intervals. This way, log-RR will be used in the analysis. Random effects model will be used to calculate the pooled effect estimates to account for both within and between study heterogeneity.

We will consider potential confounding variables and account for them in our systematic review and meta-analysis. The potential confounders expected to be there may include type of cooking fuel, duration of cooking/exposure, age, type and location of kitchen [the type of kitchen may be grouped in two groups; cooking outside, or separate kitchen inside or outside the house (low exposure); and kitchen inside the house but not separate from other rooms (high exposure)], smoking, co-morbidities etc.

To adjust for the effect of potential confounding factors on the outcome variable, meta-regression will be performed. After the collection of data, confounding will be adjusted for in the analysis stage. We will include the possible confounders as control variables in our meta-regression model; in this way, we will control for the impact of the confounding variable. Any effect that the potential confounding variable has on the effect measure will show up in the results of the meta-regression. We will undertake meta-analysis using Review Manager (RevMan). Version 5.4, (The Cochrane Collaboration). Since meta-regression cannot be performed in RevMan, it will be done using SPSS version 23 software (IBM Corp, Armonk, NY)

Subgroup analysis and investigation of heterogeneity

We will evaluate the relative risks in the prespecified subgroups where possible for age (adults or children), sex and type of fuel (wood, animal dung, charcoal, crop wastes, coal, and kerosene) and method of combustion (open fire, traditional stove, improved solid fuel stove without chimney, and improved solid fuel stove with chimney).

Ethics and dissemination

No ethical issues are foreseen. Dissemination will be done by submitting scientific articles to academic peer-reviewed journals. We will present the results at relevant conferences and meetings.


  Discussion Top


In this systematic review protocol, we clearly describe the study designs, participants, interventions, and outcomes that will be considered in line with the research question and the data sources, search strategy, data extraction, risk of bias assessment, and data synthesis.


  Conclusion Top


This systematic review will collate empirical evidence to assess the association of NCDs with the household air pollution from biomass fuel. The review findings will help the stakeholders to frame evidence-based policies and ensure that people living have clean air to breathe in their homes.

Ethical approval statement

Authors declare that appropriate review methods and quality evaluation of studies will be followed. Ethical approval is not required because only available published data will be analyzed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Household Air Pollution and Health. World Health Organization; 2021. Available from: https://www.who.int/news-room/fact-sheets/detail/household-air-pollution-and-health. [Last accessed on 2022 May 20].  Back to cited text no. 1
    
2.
WEO-2017 Special Report: Energy Access Outlook – Analysis – IEA. Available from: https://www.iea.org/reports/energy-access-outlook -2017. [Last accessed on 2022 May 23].  Back to cited text no. 2
    
3.
IARC Monographs on the Identification of Carcinogenic Hazards to Humans – International Agency for Research on Cancer. Available from: https://monographs.iarc.who.int/. [Last accessed on 2022 May 23].  Back to cited text no. 3
    
4.
Pathak U, Gupta NC, Suri JC. Risk of COPD due to indoor air pollution from biomass cooking fuel: A systematic review and meta-analysis. Int J Environ Health Res 2020;30:75-88.  Back to cited text no. 4
    
5.
Agrawal S. Effect of indoor air pollution from biomass and solid fuel combustion on prevalence of self-reported asthma among adult men and women in India: Findings from a nationwide large-scale cross-sectional survey. J Asthma 2012;49:355-65.  Back to cited text no. 5
    
6.
Indoor Air Pollution from Solid Fuels and Hypertension: A Systematic Review and Meta-Analysis – ScienceDirect. Available from: https://www.sciencedirect.com/science/article/abs/pii/S0269749119348122?via %3Dihub. [Last accessed on 2022 May 23].  Back to cited text no. 6
    
7.
The Impact of Indoor Air Pollution on Health Outcomes and Cognitive Abilities: Empirical Evidence from China | SpringerLink; 2019. Available from: https://link.springer.com/article/10.1007/s11111-019- 00317-6. [Last accessed on 2022 May 23].  Back to cited text no. 7
    
8.
Does Household use of Biomass Fuel Cause Lung Cancer? A Systematic Review and Evaluation of the Evidence for the GBD 2010 Study | Thorax. Available from: https://thorax.bmj.com/content/70/5/433.long. [Last accessed on 2022 May 23].  Back to cited text no. 8
    
9.
Raspanti GA, Hashibe M, Siwakoti B, Wei M, Thakur BK, Pun CB, et al. Household air pollution and lung cancer risk among never-smokers in Nepal. Environ Res 2016;147:141-5.  Back to cited text no. 9
    
10.
Household Air Pollution From Solid Cooking Fuel Combustion and Female Breast Cancer – PubMed. Available from: https://pubmed.ncbi.nlm.nih.gov/34422742/. [Last accessed on 2022 May 30].  Back to cited text no. 10
    




 

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