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Research Article
Revised

Cooking with biomass fuel and cardiovascular disease: a cross-sectional study among rural villagers in Phitsanulok, Thailand

[version 2; peer review: 2 approved, 1 approved with reservations]
PUBLISHED 08 Oct 2020
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This article is included in the Energy gateway.

Abstract

Background: Burning biomass fuel is a major source of indoor air pollution; about 40% of Thai people still use biomass for cooking. There is increasing evidence of the association between biomass smoke exposure and serious health effects including cardiovascular disease. The object of this cross-sectional study was to investigate the association between biomass use for household cooking and cardiovascular outcome, including coronary heart disease, hypertension, high cholesterol, diabetes mellitus, and stroke among rural villagers in Phitsanulok, Thailand. 
Methods: Data from 1078 households were collected using a face-to-face interview questionnaire. In each household, data on cardiovascular disease, cooking practices, and cooking fuel, types of fuel they normally used for cooking, were collected.
Results: After being adjusted for gender, age, cigarette smoke, secondhand smoke, and exposure to other sources of air pollution, it was found that the family members of cooks using biomass fuel were at risk of coronary heart disease (CHD; OR=4.35; 95%CI 0.10–18.97), hypertension (OR=1.61; 95%CI 1.10–2.35), high cholesterol (HC; OR=2.74; 95%CI 1.66–4.53), and diabetes (OR=1.88; 95%CI 1.03–3.46). Compared to LPG use, using wood was associated with stroke (OR=7.64; 95%CI 1.18–49.61), and using charcoal was associated with HC (OR=1.52; 95%CI 1.04–2.24). Compared to never user, household cooks who sometimes use charcoal had an increased risk of hypertension (OR=2.04; 95%CI 1.32–3.15), HC (OR=2.61; 95%CI 1.63–4.18), and diabetes (OR=2.09; 95%CI 1.17–3.73); and cooks who often use charcoal had an elevated risk of stroke (OR=3.17; 95%CI 1.04–9.71), and HC (OR=1.52; 95%CI 1.02–2.27) to their family members.
Conclusions: The study results were consistent with those found in studies from other parts of the world, and supports that exposure to biomass smoke increase cardiovascular diseases. The issue should receive more attention, and promotion of clean fuel use is a prominent action.

Keywords

Biomass fuel, cardiovascular diseases, household air pollution, kitchen smoke, cooking fume

Revised Amendments from Version 1

In this version, the term cooking fuel and cooking smoke was clarified. In statistical analysis, more information was added and the regression model use was precisely described.

See the authors' detailed response to the review by Nilima Barman

Introduction

Cooking smoke is a major source of household air pollution, which affects billions of people around the world, especially in developing countries. Globally, nearly 3 billion people still use solid fuels (wood, charcoal, crop residues, and dung) for cooking and heating1. Smoke from wood burning contains a large number of pollutants, including particulate matter, carbon monoxide, nitrogen dioxide, formaldehyde, and a number of highly toxic organic compounds, such as benzene, 1, 3 butadiene, benzo[a]pyrene and other toxic polycyclic aromatic hydrocarbons2. In addition to fuel burning smoke, overheated of cooking oils might also produce smoke which depended on several factors, including cooking oils, cooking methods, cooking equipment, and food types3

The use of solid fuel for cooking and/or household energy sources increases respiratory and non-respiratory illnesses in both adults and children. Those effects that are well established are acute respiratory infections, chronic obstructive pulmonary disease (COPD), lung cancer, asthma, tuberculosis, and cataracts4,5. In children, biomass use is related to mortality, and acute lower respiratory tract infections, and some other non-respiratory illness, such as poor lung function, low birthweight, nutritional deficiency, and impairment of learning ability5,6.

Though with limited evidence, recent studies linked biomass smoke exposure and cardiovascular diseases (CVD), e.g. coronary heart disease (CHD), hypertension, diabetes, and stroke811. In laboratory studies, chronic exposure to biomass smoke increased the thickness and plaque of blood vessels11. In epidemiological studies, Peruvians who live in high altitude environments and use biomass fuel had an elevated prevalence of hypertension13. A study among villager women in Bangladesh reported an association between elevated cumulative exposure to biomass smoke and the prevalence of hypertension14. A similar result was found in a study in Shanghai Putuo, which found using solid fuel increases the risk of hypertension, CHD, and diabetes15; and a study in Shanxi, China reported an increased risk of hypertension, CHD, stroke, diabetes, and dyslipidemia16. A recent study by Yu et al.17 also linked solid fuel use to cardiovascular mortality.

On a global scale, CVD is the number one cause of death and is responsible for about 18 million deaths annually18. In Thailand, CVD accounts for 23% of the national mortality19. Currently, there is no study on the effect of biomass smoke on CVD in Thailand. It was reported that about 40% of Thai households still use biomass, mainly charcoal, wood, and agriculture residue, for cooking20. The objective of this study is to investigate a possible association between biomass use for cooking and cardiovascular diseases, including CHD, hypertension, HC, diabetes, and stroke. The study uses data from a cross-sectional survey among rural villagers in Phitsanulok, Thailand. The result could be used for disease prevention and control, and to support the global literature.

Methods

Study design and setting

This is cross-sectional study. Participants are rural villagers living in Phitsanulok Province, Thailand. Phitsanulok is a midsize province located about 400 km north of Bangkok. There are 866,891 people in the area of 9 districts. Most of the people are rice farmers21.

Study participants and sampling procedure

Participants were randomly selected using multistage sampling. Out of the 9 districts in Phitsanulok province, 5 were randomly selected. In each district, one sub-district and a local health-promoting hospital were approached. In each sub-district with support from the local health-promoting hospital, a total of 1,150 households were approached and 1,134 (98.6%) people agreed to participate in the study. In each household, only one participant who was responsible for household cooking and aged over 20 years was selected. After data cleanup, 56 (4.9%) items of data were missing important information, such as age, gender, cooking practice. The final data from 1,078 people were used for statistical analysis.

The minimum sample size was calculated to be 1,034, using unmatched cross-sectional study with the following assumptions: two-sided significance level = 95%; power of detection = 80%; percent unexposed with outcome = 5%; and odds ratio = 2.0.

Study questionnaire

Data was collected using a face-to-face interview questionnaire, which was administered by 15 village health volunteers (provided as Extended data in English22). The interviews took place in the house of participants. The data was collected during the period of May–June 2017. Health volunteers were all trained on how to properly carry out the interview and use the questionnaire. The questionnaire was designed to collect information on demographic data, fuel use for cooking, and other cooking practices. In addition to general demographic data, participants were also asked a history of tobacco use (ever, never), and working in factory environments using “yes” or “no” questions. Ever smoker referred to those who smoke more than 100 cigarettes in their lifetime. Data on pesticide use was also measured by “yes” or “no” questions: “Have you ever spray or mix pesticide?”. For cooking fuel data, we asked about the types of fuel they used for cooking food (wood, charcoal, LPG, electricity), and the frequency of using each types of fuel. Data collected on cooking practices were types of cooking oil, the frequency of tears while cooking (TWC) (never, sometimes, often), kitchen location (inside a house, outside a house, both inside and outside a house), and the characteristics of kitchen ventilation (good or poor ventilation).

The presence of cardiovascular disease was determined by the participant response to the question: “Have you ever been diagnosed with the following diseases (coronary heart disease (CHD), hypertension, high cholesterol (HC), diabetes mellitus, stroke) by a medical doctor?”. For diseases among their family members, we asked “Did you have a family member with the following diseases?”.

The content validity of the questions was tested by three experts, and the Index of Item Objective Congruence (IOC) was between 0.7–1.0. The questionnaire was also tested for question sequencing and understanding using a group of 30 people with a similar background to the intended participants.

Statistical analysis

Demographic and prevalence of cardiovascular disease were descriptively analyzed. Comparison between groups were analyzed using chi-square test for categorical variables, and independent t-test for continuous variables. The association between cardiovascular disease was analyzed using binary multiple logistic regression with odds ratios (OR) and 95 percent confidence interval (CI) adjusted for gender (male, female), age (continuous data), cigarette smoking (ever, never), living smoker (yes, no), working with smokers (yes, no), and exposure to air pollution (yes, no). These adjusted variables of the repondents were used also when analysis for ORs of disease risk among the respondents’ family members. All statistical analyses were performed using IBM SPSS version 19 and OpenEpi (online version 3.01). Statistical significance was set at a p-value of less than 0.05.

Ethical considerations

The study was approved by the Ethical Committee of Naresuan University (COA No. 485/2016), and written informed consent from the respondents was obtained before the interviews were conducted.

Results

Most of the respondents were women (84.2%) with a mean age of 53.04 ± 12.93 yr. The highest education levels were primary school or high school. Most were farmers (36.0%) and 20.2% were causal workers on farms. About 10% were smokers and 33% lived with a smoker. Additional information on the demographic data is shown in Table 1 and in Underlying data23.

Table 1. Demographic data.

Characteristics (N=1078)N (%)
Gender
Male170 (15.8)
Female908 (84.2)
Age (yr.)
20–3067 (6.2)
31–40136 (12.6)
41–50205 (19.0)
51–60343 (31.8)
61–70258 (23.9)
71–8069 (6.4)
Mean = 53.04 ± 12.93 (Age range 20–80 yr.)
Education completed
Primary school757 (71.9)
Secondary school246 (23.4)
College diploma50 (4.8)
Missing25 (2.3)
Occupation
Farmer388 (36.0)
Grocer89 (8.3)
Private or government employee57 (5.3)
Causal worker218 (20.2)
Housewife223 (20.7)
Other/unemployed103 (9.6)
Cigarette smoking
Ever smoke111 (10.3)
Never smoke967 (89.7)
Living with smokers
Yes362 (33.8)
No710 (66.2)
Missing6 (0.6)
Working with smokers
Yes172 (16.1)
No895 (83.9)
Working in a factory
Yes175 (16.4)
No894 (83.6)
Missing9 (0.8)
Spray or mix pesticides
Yes425 (39.5)
No651 (60.5)
Missing4 (0.4)
Fuel use for cooking
Wood27 (2.5)
Charcoal348 (32.3)
LPG695 (64.5)
Electricity8 (0.7)
Frequency of using charcoal
Never495 (46.4)
1–2 times per week160 (15.0)
3 times per week or more411 (38.6)
Kitchen location
Inside a house570 (53.4)
Both inside and outside134 (12.6)
Outside a house363 (34.0)
Tears while cooking
Often49 (4.6)
Sometimes537 (50.8)
Never472 (44.6)
Missing20 (1.9)
Cooking frequency
Everyday984 (91.3)
Somedays94 (8.7)
Using charcoal duration (year)
Not use502 (46.6)
1–20146 (13.6)
21 or more429 (39.8)

About 70% of the respondents reported using biomass for cooking (Table 2). However, when asked for fuel types that they usually use for cooking, 64.5% reported LPG and 32.3% charcoal. Among those who use charcoal, 38.6% use it often. About half have a kitchen located inside a house with good ventilation. Almost all reported having TWC either sometimes or often. Most of them cook every day.

Table 2. Demographic data among biomass and LPG users.

CharacteristicsBiomass, n (%)LPG, n (%)P–value*
Gender
Male114 (15.1)56 (17.4)0.341
Female642 (84.9)266 (82.6)
Age
20–3034 (4.5)33 (10.2)<0.001**
31–4089 (11.8)47 (14.6)
41–50132 (17.5)73 (22.7)
51–60249 (32.9)94 (29.2)
61–70204 (27.0)54 (16.8)
71–8048 (6.3)21 (6.5)
Education
completed
<0.001**
Primary school569 (76.9)188 (60.1)
Secondary school142 (19.2)104 (33.2)
College diploma or
higher
29 (3.9)21 (6.7)
Missing16 (2.1)9 (2.8)
Occupation<0.001**
Farmer299 (39.6)89 (27.6)
Grocer54 (7.1)35 (10.9)
Private or
government
employee
36 (4.8)21 (6.5)
Causal worker130 (17.2)88 (27.3)
Housewife161 (21.3)62 (19.3)
other76 (10.1)27 (8.4)
Cigarette
smoking
0.490
Ever smoke81 (10.7)30 (9.3)
Never smoke675 (89.3)292 (90.7)
Living with
smokers
0.475
Yes259 (34.4)103 (32.2)
No493 (65.6)217 (67.8)
Missing4 (0.5)2 (0.6)
Working with
smokers
0.054
Yes131 (17.5)41 (12.8)
No616 (82.5)279 (87.2)
Missing9 (1.2)2 (0.6)
Working in a
factory
0.077
Yes113 (15.1)62 (19.4)
No637 (84.9)257 (80.6)
Missing6 (0.8)3 (0.9)
Using pesticides0.001**
Yes321 (42.6)104 (32.3)
No433 (57.4)218 (67.7)
Missing2 (0.3)
Kitchen location<0.001**
Inside a house364 (48.6)206 (64.8)
Both inside and
outside
109 (14.6)25 (7.9)
Outside a house276 (36.8)87 (27.4)
Kitchen
ventilation
0.580
Good504 (96.9)247 (97.6)
Poor16 (3.1)6 (2.4)
Cooking
frequency
0.035**
Everyday699 (92.5)285 (88.5)
Someday57 (7.5)37 (11.5)

* P–value of chi square test for difference between biomass user and not use group, 2–trailed test

** Significantly difference, p <0.05

The study found hypertension, HC, and diabetes to be the most common cardiovascular outcomes (Table 3). Compared to non-user group, biomass users had a significantly higher prevalence of hypertension, and HC, and their family members also had more incidence of hypertension, HC, diabetes, and heart disease.

Table 3. Prevalence of cardiovascular diseases among biomass and LPG users.

DiseaseBiomass, n/total n (%)LPG, n/total n (%)p–value*
Hypertension(R)a214/750 (28.5)66/321 (20.6)0.007**
Hypertension(F)b152/729 (21.0)44/305 (14.4)0.014**
High cholesterol, HC(R)166/748 (22.2)48/320 (15.0)0.007**
High cholesterol, HC(F)120/729 (16.5)21/305 (6.9)<0.001**
Diabetes(R)91/751 (12.1)30/321 (9.3)0.189
Diabetes (F)62/729 (8.5)14/305 (4.6)0.028**
Coronary heart disease, CHD(R)20/749 (2.7)6/321 (1.9)0.521
Coronary heart disease, CHD(F)20/728 (2.7)2/304 (0.7)0.034**
Stroke(R)10/750 (1.3)3/321 (0.9)0.585
Stroke (F)16/729 (2.2)3/305 (1.0)0.186

a disease of respondent (R)

b disease of respondent’s family member (F)

* P–value of chi square test for difference between diseases prevalence among biomass use and LPG use

** Significant at P < 0.05, 2-tailed test

Further analysis using logistic regression and control variables, revealed that compared to gas users, biomass users had family members with elevated CHD, hypertension, HC, and diabetes (Table 4). Among different types of fuel, household cooks using wood had a significant elevated risk of CHD (OR=7.64, 95%CI 1.18-49.61), and their family members had an elevated risk of HC (OR=1.52, 95%CI 1.04-2.24). Comparing frequency of charcoal use, those who use charcoal sometimes or often are more likely to have CHD, hypertension, HC, and diabetes as compared to those who never use charcoal. The family members of charcoal users also had a significant increase of HC and stroke. When using TWC as an indicator for smoke exposure, it was found that those who always had TWC had significantly increased risk of stroke (OR=2.16; 95%CI 1.08-4.32), and those with sometimes TWC had a CHD risk (OR=2.64; 95%CI 1.02-6.81). Regarding kitchen location, the family members of cooks having kitchens both inside and outside a house had an elevated risk of stroke (OR=4.60; 95%CI 1.14-18.54).

Table 4. Association (OR)* between biomass use and cardiovascular outcomes.

Hypertensio(R)(F)HC(R)HC(F)Diabetes(R)Diabetes(F)CHD(R)CHD(F)Stroke(R)Stroke (F)
Biomass use
Yes1.27 (0.91–1.77)1.61 (1.10–2.35)1.28 (0.88–1.86)2.74 (1.66–4.53)1.08 (0.69–1.70)1.88 (1.03–3.46)1.18 (0.46–3.02)4.35 (0.10–18.971.27 (0.33–4.87)4.45 (0.97–20.56)
No1.01.01.01.01.01.01.01.01.01.0
Fuel type
Wood1.11 (0.45–2.74)1.93 (0.77–4.85)1.31 (0.51–3.36)1.45 (0.47–4.41)0.58 (0.13–2.59)2.11 (0.59–7.48)1.63 (0.19–13.66)NA7.64 (1.18–
49.61)
0.72 (0.27–1.96)
Charcoal0.79 (0.57–1.09)1.22 (0.86–1.72)0.89 (0.63–1.26)1.52 (1.04–2.24)0.97 (0.63–1.48)1.47 (0.89–2.43)1.14 (0.49–2.65)1.54 (0.64–3.73))2.03 (0.58–7.09)0.93 (0.68–1.26)
LPG/Electric1.01.01.01.01.01.01.01.01.01.0
Charcoal use
Often1.10 (0.79–1.52)1.10 (0.77–1.57)1.30 (0.90–1.87)1.52 (1.02–2.27)1.44 (0.92–2.26)1.56 (0.94–2.61)1.33 (0.51–3.48)1.37 (0.52–3.63)1.66 (0.44–6.29)3.17 (1.04–9.71)
Sometimes2.04 (1.32–3.15)1.28 (0.80–2.04)2.61 (1.63–4.18)1.11(0.63–1.96)2.09 (1.17–3.73)0.69 (0.29–1.61)4.11 (1.40–12.11)1.50 (0.44–5.18)2.76 (0.56–13.50)0.59 (0.07–5.21)
Never1.01.01.01.01.01.01.01.01.01.0
Tears while cooking
Often0.84 (0.41–1.73)0.71 (0.31–1.65)0.56 (0.23–1.35)0.76 (0.29–2.01)0.93 (0.34–2.55)0.23 (0.03–1.75)3.45 (0.66–17.94)1.07 (0.13–8.78)2.16 (1.08–4.32)1.80 (0.96–3.35)
Sometimes0.82 (0.61–1.11)0.96 (0.69–1.34)0.92 (0.66–1.28)1.02 (0.70–1.49)1.17 (0.78–1.77)0.80 (0.49–1.29)2.64 (1.02–6.81)1.13 (0.47–2.73)0.98 (0.69–1.41)1.04 (0.78–1.40)
Rarely1.01.01.01.01.01.01.01.01.01.0
Kitchen location
Inside0.80 (0.58–1.11)0.94 (0.67–1.34)1.11 (0.78–1.58)1.07 (0.72–1.60)0.83 (0.54–1.27)0.71 (0.42–1.18)2.14 (0.77–5.92)2.11 (0.75–5.93)1.89 (0.45–7.89)1.87 (0.55–6.33)
Both1.00 (0.61–1.64)1.08 (0.64–1.83)0.85 (0.48–1.51)0.84 (0.44–1.61)1.17 (0.62–2.20)0.76 (0.35–1.65)1.96 (0.45–8.55)0.50 (0.06–4.36)4.62 (0.81–26.47)4.60 (1.14–18.54)
Outside1.01.01.01.01.01.01.01.01.01.0
Charcoal use
Often1.10 (0.79–1.52)1.10 (0.77–1.57)1.30 (0.90–1.87)1.52 (1.02–2.27)1.44 (0.92–2.26)1.56 (0.94–2.61)1.33 (0.51–3.48)1.37 (0.52–3.63)1.66 (0.44–6.29)3.17 (1.04–9.71)
Sometimes2.04 (1.32–3.15)1.28 (0.80–2.04)2.61 (1.63–4.18)1.11(0.63–1.96)2.09 (1.17–3.73)0.69 (0.29–1.61)4.11 (1.40–12.11)1.50 (0.44–5.18)2.76 (0.56–13.50)0.59 (0.07–5.21)
Never1.01.01.01.01.01.01.01.01.01.0
Using charcoal location
Inside0.95 (0.62–1.45)0.89 (0.56–1.42)1.26 (0.81–1.96)1.40 (0.84–2.34)0.72 (0.41–1.26)0.83 (0.41–1.66)2.13 (0.75–6.09)4.71 (1.36–16.32)1.32 (0.27–6.42)2.46 (0.67–9.01)
Both2.03 (0.89–4.63)0.64 (0.21–1.92)1.32 (0.54–3.25)1.18 (0.38–3.64)1.19 (0.42–3.38)0.84 (0.19–3.78)1.46 (0.16–13.01)2.83 (0.30–27.07)3.35 (0.24–47.21)2.19 (0.22–21.51)
Outside1.01.01.01.01.01.01.01.01.01.0
Using charcoal duration (year)
>201.38 (1.01–1.89)1.05 (0.74–1.50)1.73 (1.22–2.44)1.34 (0.89–2.01)1.50 (0.98–2.30)1.55 (0.93–2.57)1.36 (0.99–1.87)1.49 (0.60–3.74)2.39 (0.70–8.24)1.63 (0.51–5.19)
1–201.28 (0.78–2.12)1.40 (0.87–2.25)1.25 (0.70–2.22)1.54 (0.89–2.68)1.31 (0.65–2.63)0.55 (0.21–1.46)1.28 (0.77–2.11)0.71 (0.15–3.46)NA2.62 (0.75–9.16)
Not use1.01.01.01.01.01.01.01.01.01.0
Years of
using
charcoal o
1.003
(0.996–1.010)
1.003
(0.995–1.011)
1.010
(1.002–1.017)
1.007
(0.998–1.016)
1.004
(0.995–1.013)
1.013
(1.001–1.024)
1.015
(0.997–1.034)
1.012
(0.990–1.033)
1.014
(0.989–1.039)
1.011
(0.986–1.037)

*Logistic regression, adjusted for gender (male, female), age (continuous), cigarette smoking (ever, never), living with smoker (yes, no), working with smoker (yes, no), pesticide use (yes, no), working in a factory (yes, no)

Significant value (p<0.05) is given in bold letters

Discussion

This study presented an association between cardiovascular diseases and exposure to smoke from biomass, mainly charcoal, which is relatively cleaner when compared to wood, coal, or dung, a biomass which were often found in the literature. The study also showed that biomass use not only affects household cooks but also their family members. It was found that biomass users have a higher prevalence of hypertension and HC, and their family members had a higher prevalence of hypertension, HC, diabetes, and CHD (Table 3). Further analysis using logistic regression and control for potential confounder showed a significant OR of biomass use and CHD(F), hypertension(F), HC(F), and diabetes(F) (Table 4). Compared to LPG, wood use also had a strong association with stroke (OR=7.64; 95%CI 1.18–49.61). Among charcoal users, those who use it sometimes or often had an elevated risk of CHD, hypertension, HC, and diabetes for themselves, and risk of HC and stroke for their family members. The results are consistent with the literature. Previous research found biomass smoke contains a lot of pollutants, especially fine particulates, and carbon monoxide which are known to cause cardiovascular effects2. In laboratory studies, biomass smoke exposure was associated with endothelial inflammation23.

For hypertension, we found both cooks and their family members have a higher prevalence of hypertension (Table 3). Further analysis indicated an elevated risk of hypertension (OR=1.61; 95%CI 1.10–2.35) among family members of cooks using biomass for cooking (Table 4). As compared to those who never use it, cooks who sometimes use charcoal have twice the risk of hypertension (OR=2.04; 95%CI 1.32–3.15) and those who use charcoal over twenty years have 1.38 times the risk of hypertension (OR=1.38; 95%CI 1.01–1.89). In the literature, there is increasing evidence to link biomass smoke and hypertension25,26. A study in Peru found that biomass users had an increased risk of both prehypertension (OR=5.0; 95%CI 2.6–9.9), and hypertension (OR=3.5; 95%CI 1.7–7.0)13. In Bangladesh, it was found that among rural women, one additional year of biomass smoke exposure to increase risk of hypertension by 61% (OR=1.61; 95%CI 1.16–2.22)14. Recent studies in Honduras also linked PM2.5 and black carbon exposure and hypertension among women using traditional and improved stoves26.

The current study also found a higher prevalence of HC among cooks and their family members using biomass fuel (Table 3) with a significant OR of 2.74 (95%CI 1.66–4.53) for family members (Table 4). The result showed a difference in the risk of HC among those who use wood, charcoal, and LPG. This risk also varied particularly according to the frequency of charcoal use. Compared to nonusers, an elevated risk of HC was found among cooks who sometimes use charcoal (OR=2.04; 95%CI 1.32–3.15), and among those who use charcoal over 20 years (OR=1.73; 95%CI 1.22–2.44). Among cooks, every year of using charcoal will increase risk of HC by about 1% (OR=1.010; 95%CI 1.002–1.017). Risk of HC was also increased among family members of cooks who often use charcoal (OR=1.52; 95%CI 1.02–2.27). Though the evidence was limited, other studies have found an association between cholesterol and COPD, a disease often found among biomass users3. A study in Ghana also found a strong association between wood smoke exposure and several hematological and biochemical indices, including HC (OR=20.44; 95%CI 2.610–160.2)27. The higher OR might be explained by the difference in biomass types, which was found to be wood in other studies, while most of respondents in this study use charcoal which is relatively cleaner.

We found about 10% of the respondents had type 2 diabetes and the prevalence of the disease was higher among biomass users (Table 3). Logistic regression analysis revealed a significant risk of diabetes among cooks using charcoal sometimes (OR=2.09; 95%CI 1.17–3.73) as compared to the never user group (Table 4). Among family members of cooks, risk of diabetes was elevated by using biomass fuel (OR=1.88; 95%CI 1.03–3.46), and years of using charcoal (OR=1.013; 95%CI 1.001–1.024). Similar results have also been reported by several studies on the effect of particulate matter or traffic-related air pollutants on diabetes28. In addition, experimental studies may provide potential mechanisms, including glucose homeostasis, systemic inflammation, stress in the liver and endoplasmic reticulum, and alterations of mitochondrial and other adipose tissue29. Currently, epidemiological studies on the effect of indoor air pollution on diabetes are rare. A study of women in Honduras reported an association between the prevalence of prediabetes/diabetes and PM2.5 in kitchen biomass cooking stoves30. This was consistent with the results from a previous study from Shanghai Putuo, which also found an elevated risk of several cardiovascular diseases including diabetes (OR=2.48; 95%CI 1.59–3.86) among people using solid fuel at home15.

Those who use biomass for cooking had a risk of CHD 4.35 times (95%CI 0.10–18.97) of LPG users; and those using charcoal sometimes had risk of CHD 4.11 times (95%CI 1.40–12.11) of never user group. These results are consistent with evidence from cigarette smoke and ambient air pollution. In animal studies, biomass fuel smoke caused arteriosclerotic effects in animal blood vessels12. Studies found COPD as a risk factor of CHD31; and our previous study found elevated chronic symptoms, such as chronic cough, dyspnea and runny nose which is a sign of COPD among cooks using biomass fuel for cooking3. Epidemiological studies also reported an association between solid fuel smoke exposure and CHD32. A study in Pakistan found that rural women who currently use solid fuel had an increased risk of acute coronary syndrome (OR=4.8; 95%CI 1.5–14.8)33. This is consistent with a study from Shanghai Putuo, which found solid fuel use in the home is associated with CHD (OR=2.58; 95%CI 1.53–4.32)15, and study from Shanxi, China found an elevated risk of CHD (OR=2.25) among solid fuel users16.

In this study, respondents who use wood (OR=7.64; 95%CI 1.18–49.61) and charcoal (OR=2.03; 95%CI 0.58–7.09) had an elevated risk of stroke as compared to clean fuel users (Table 4). Among charcoal users, those using charcoal sometimes (OR=1.66; 95%CI 0.44–6.29) and often (OR=2.76; 95%CI 0.56–13.50) seem to have a higher risk of stroke but a significant elevation was found only among the family members of cooks using charcoal often (OR=3.17; 95%CI 1.04–9.71). This was consistent with the literature. The association between household solid fuel use and stoke were also reported in a study from Shanghai Putuo (OR=1.87; 95% CI 1.03–3.38)15, and study from Shanxi, China (OR=1.64)16. In ambient settings, a long-term effect of PM exposure on cardiovascular disease, including stroke, was well established34. It was estimated that for each 10 µg/m3 increment in PM10, risk of overall stroke events will increase by 1.06 times (95%CI 1.02–1.11), and the risk of stoke mortality by 1.08 times (95%CI 0.99–1.18)35.

One potential drawback of this study was the use of self-reported data of diseases. Without the confirmation of medical records, the survey diseases are subjected to information bias. However, the bias will be distributed equally to all comparison groups, and this tends to underestimate the result. The number of participants included in this study was also rather small to detect the actual association of a rare disease, e.g. stroke. By using cross-sectional design, the study result cannot explain the causal relationship, because it is not known whether exposure or the disease occurred first. However, the problem is minimal for rare diseases.

Conclusions

The results from this study support research findings in other part of the world that using biomass for cooking increases the risk of cardiovascular diseases. This study also confirms the negative effects of using charcoal, which is considered to be a relatively cleaner fuel as compared with wood, dung, coal, and other agricultural residues. Concerned organizations should pay more attention to the issue and promote clean fuel usage.

Data availability

Underlying data

Figshare: Household cooking and cardiovascular diseases, https://doi.org/10.6084/m9.figshare.12117066.v223.

This project contains the following underlying data:

  • Household cooking and cardiovascular diseases.sav (Collected demographic and cardiovascular diseases data)

  • Data dictionary.docx (Word document containing dictionary for study dataset)

Extended data

Figshare: Questionnaire-household cooking and cardiovascular disease, https://doi.org/10.6084/m9.figshare.12121887.v222.

This project contains the following extended data:

  • Questionnaire-household cooking and cardiovascular disease.docx (Study questionnaire in English)

  • Questionnaire-household cooking and cardiovascular disease-Thai.docx (Study questionnaire in Thai)

Data are available under the terms of the Creative Commons Zero "No rights reserved" data waiver (CC0 1.0 Public domain dedication).

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Juntarawijit C and Juntarawijit Y. Cooking with biomass fuel and cardiovascular disease: a cross-sectional study among rural villagers in Phitsanulok, Thailand [version 2; peer review: 2 approved, 1 approved with reservations]. F1000Research 2020, 9:307 (https://doi.org/10.12688/f1000research.23457.2)
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ApprovedThe paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approvedFundamental flaws in the paper seriously undermine the findings and conclusions
Version 2
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Reviewer Report 05 Nov 2020
Ogonna N.O. Nwankwo, Department of Community Medicine, University of Calabar Teaching Hospital, Calabar, Nigeria 
Approved with Reservations
VIEWS 7
First off, thank you for setting out to provide more evidence on this important public health issue that affects a large proportion of people globally.
I will categorize my comments under major and minor issues with the manuscripts that ... Continue reading
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Nwankwo ONO. Reviewer Report For: Cooking with biomass fuel and cardiovascular disease: a cross-sectional study among rural villagers in Phitsanulok, Thailand [version 2; peer review: 2 approved, 1 approved with reservations]. F1000Research 2020, 9:307 (https://doi.org/10.5256/f1000research.29890.r72717)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
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Reviewer Report 09 Oct 2020
Nilima Barman, Department of Laboratory Medicine, Bangladesh Institute of Research and Rehabilitation for Diabetes, Endocrine and Metabolic Disorders (BIRDEM), Dhaka, Bangladesh 
Approved
VIEWS 5
Now the article is more precise. The authors has addressed most ... Continue reading
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Barman N. Reviewer Report For: Cooking with biomass fuel and cardiovascular disease: a cross-sectional study among rural villagers in Phitsanulok, Thailand [version 2; peer review: 2 approved, 1 approved with reservations]. F1000Research 2020, 9:307 (https://doi.org/10.5256/f1000research.29890.r72681)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
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PUBLISHED 29 Apr 2020
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Reviewer Report 22 Sep 2020
Nilima Barman, Department of Laboratory Medicine, Bangladesh Institute of Research and Rehabilitation for Diabetes, Endocrine and Metabolic Disorders (BIRDEM), Dhaka, Bangladesh 
Approved with Reservations
VIEWS 17
The article has emphasized on detrimental effects of biomass cooking fuel on cardiovascular health. The results will help in future policy making regarding cooking fuel. The overall article is well-written but some of the issues need to be clarified as ... Continue reading
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Barman N. Reviewer Report For: Cooking with biomass fuel and cardiovascular disease: a cross-sectional study among rural villagers in Phitsanulok, Thailand [version 2; peer review: 2 approved, 1 approved with reservations]. F1000Research 2020, 9:307 (https://doi.org/10.5256/f1000research.25888.r71210)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.
  • Author Response 08 Oct 2020
    Chudchawal Juntarawijit, Department of Natural Resources and Environment, Faculty of Agriculture, Natural Resources, and Environment, Naresuan University, Phitsanulok, 65000, Thailand
    08 Oct 2020
    Author Response
    Response to reviewer

    In the abstract:

    Comments: The methods should be improved, giving a clear description of cooking fuel.
     
    Responses: A short description of cooking fuel was added to the methods section. ... Continue reading
COMMENTS ON THIS REPORT
  • Author Response 08 Oct 2020
    Chudchawal Juntarawijit, Department of Natural Resources and Environment, Faculty of Agriculture, Natural Resources, and Environment, Naresuan University, Phitsanulok, 65000, Thailand
    08 Oct 2020
    Author Response
    Response to reviewer

    In the abstract:

    Comments: The methods should be improved, giving a clear description of cooking fuel.
     
    Responses: A short description of cooking fuel was added to the methods section. ... Continue reading
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Reviewer Report 19 May 2020
Thandi Puoane, School of Public Health, University of the Western Cape, Bellville, South Africa 
Lungiswa Tsolekile, School of Public Health, University of the Western Cape, Bellville, South Africa 
Approved
VIEWS 8
A cross-sectional study undertaken to investigate a possible association between biomass use for cooking and cardiovascular diseases, including CHD, HBP, HC, diabetes, and stroke. Biomass users had a significantly higher prevalence of HBP, and HC, and their family members also ... Continue reading
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CITE
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Puoane T and Tsolekile L. Reviewer Report For: Cooking with biomass fuel and cardiovascular disease: a cross-sectional study among rural villagers in Phitsanulok, Thailand [version 2; peer review: 2 approved, 1 approved with reservations]. F1000Research 2020, 9:307 (https://doi.org/10.5256/f1000research.25888.r62897)
NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article.

Comments on this article Comments (0)

Version 2
VERSION 2 PUBLISHED 29 Apr 2020
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Alongside their report, reviewers assign a status to the article:
Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested
Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.
Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions
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