Wuhan, China — On April 3, 2018, supported by the National Natural Science Foundation of China, the research team directed by Prof. Wu Tangchun at the Huazhong University of Science and Technology, Prof. Li Liming at the Peking University, and Prof. Chen Zhengming at the Oxford University published an original research entitled “Association of Solid Fuel Use with Risk of Cardiovascular and All-Cause Mortality in Rural China” on JAMA (impact factor=44.4), which was co-authored by Dr. Yu Kuai ( Huazhong University of Science and Technology), Dr. Qiu Gaokun (Huazhong University of Science and Technology) and Dr. Chan Ka-Hung (Oxford University).
Cooking and heating are the prime requirements for human survival and development. During recent decades, the rapid economic transition worldwide has witnessed the emergence of different fuel types for cooking and heating, including clean fuels such as gas, electricity and central heating, and traditional solid fuels such as coal and biomass. Solid fuel use is a major impediment of realization of a decent living for about 3 billion people globally, mostly from low- and middle-income countries.
When combusted indoors, solid fuels emit a large amount of pollutants such as fine particulate matter (PM2.5), carbon monoxide and nitrogen monoxide than, which in ambient air is an established risk factor for mortality. According to the Global Burden of Disease Study, it has been estimated that solid fuel use for cooking contributes up to 37% of global PM2.5 levels, while solid fuels use for heating contributes up to 21%. Although solid fuels use, the leading cause of household air pollution, has become a major public health concern, reliable epidemiological evidence remains scarce, especially on the association between solid fuel use and cardiovascular mortality. Furthermore, it remains unclear whether mortality risk associated with solid fuel use is lower among adults who had switched from solid to clean fuel use or used appropriate ventilation.
Based on the China Kadoorie Biobank study, the present study included participants from five rural areas (Sichuan, Gansu, Henan, Zhejiang, and Hunan) for only 7.1% and 12.8%, respectively, of the participants from urban areas used solid fuels for cooking or heating. Among the 271217 participants, about 66% of the participants reported regular cooking and 60% reported winter heating, of whom 84% and 90% still used solid fuels, respectively.
The study group found that, compared with reported clean fuel use for cooking, solid fuel use was associated significantly with higher risk of cardiovascular mortality (absolute rate difference [ARD] per 100,000 person-years, 135; hazard ratio [HR], 1.20) and all-cause mortality (ARD, 338; HR, 1.11). For heating, higher risk was also observed in association with reported solid fuel use for cardiovascular (ARD, 175; HR, 1.29) and all-cause mortality (ARD, 392; HR, 1.14 for all-cause mortality). Participants with longer self-reported duration of solid fuel use had higher risks of cardiovascular and all-cause mortality.
Notably, this study is the first to distinguish the effect attributed to the use of solid fuels for cooking and that for heating, and finds that increased mortality risk from cooking and heating with solid fuels is independent of each other.
This study adds strong scientific evidence to the impact of indoor air pollution on health. Compared with persistent solid fuel users, participants who reported having previously switched from for cooking had lower risk of cardiovascular (ARD, 138; HR, 0.83) and all-cause mortality (ARD, 407; HR, 0.87), while for heating the ARDs were 93 and 492, and HRs were 0.57 and 0.67, respectively. Among solid fuel users, use of ventilated cookstoves was also associated with lower risk of cardiovascular (ARD, 33; HR, 0.89) and all-cause mortality (ARD, 87; HR, 0.91).
To our knowledge, this is the largest prospective cohort study to date investigating the association of solid fuel use with mortality risk. Apart from the large sample size, the main strengths of this study also include the prospective design, and the inclusion of participants from five diverse rural areas, thereby permitting detailed examination of the association between solid fuel use and mortality risk in different settings.
Moreover, to our knowledge, this study is the first to assess the mortality risk associated with cooking and heating separately, their additive interactions with smoking, as well as switching from solid fuels to clean fuels and use of appropriate ventilation.
These findings emphasize the importance of reducing solid fuel use and also highlight that when substitution with clean fuel is not feasible, the use of ventilation might serve as an alternative strategy to lessen mortality risk, which could be of particular public health significance in less-developed areas. To assess the reproducibility, about 4% of the original participants were randomly selected for a resurvey after completion of the baseline survey, collecting same information as baseline, and the weighted kappa values indicate a good reproducibility. To guarantee the reliability of our findings, this study not only controlled an extensive list of potential confounders (e.g., age, sex, study area, education, household income level, smoking status, drinking status, passive smoking, diet, physical activity, body mass index, stove ventilation, etc.), but also performed stratification analysis by fuel types, cardiovascular death subtypes and study areas, and a series of sensitivity analyses (e.g., additional adjustment for survey season, occupation, self-rated health status, family history of cardiovascular disease; excluding those taking anti-hypertensive treatment, those using clean fuels for less than 10 years and excluding events occurring during the first 2 years of follow-up). The major limitation of this study is the lack of direct measurement of household air pollution exposure.
In conclusion, we found that rural Chinese adults who used solid fuels for cooking or for heating had an elevated risk of cardiovascular and all-cause mortality. Switching from solid to clean fuels and use of ventilation attenuated the risks. Our findings underscore the importance of reducing solid fuel use, or using ventilation if clean fuel is not affordable, to lessen mortality risk.
Chinese News Link: http://gwxy.tjmu.edu.cn/info/1067/2199.htm
For more details, please refer to: https://jamanetwork.com/journals/jama/article-abstract/2677446?
Extensive reading: China Kadoorie Biobank
The China Kadoorie Biobank (CKB), known previously as the Kadoorie Study of Chronic Disease in China (KSCDC), is set up to investigate the main genetic and environmental causes of common chronic diseases in the Chinese population. During 2004-2008, over 510,000 adults were recruited from 10 geographically defined regions of China, with extensive data collection by questionnaire and physical measurements, and with long-term storage of blood samples for future study. All the participants are now being closely monitored for death and other health-related outcomes through linkage with established registries and health insurance databases in the study areas. This large, well-established, study will be a uniquely powerful and rich resource for investigating the main causes of many common chronic diseases over the next few decades, and the information generated will advance our understanding of disease aetiology not only in China but also in other countries.
For more details, please refer to: http://www.ckbiobank.org/site/
