Abstract
BackgroundHarmful substances in solid fuel and tobacco smoke are believed to enter the bloodstream via inhalation and to be metabolized in the liver, leading to chronic liver damage. However, little is known about the independent and joint effects of solid fuel use and smoking on risks of chronic liver disease (CLD) mortality.MethodsDuring 2004–08, ∼0.5 million adults aged 30–79 years were recruited from 10 areas across China. During a 10-year median follow-up, 2461 CLD deaths were recorded. Multivariable Cox regression yielded adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the individual associations of self-reported long-term cooking fuel and tobacco use with major CLD death.ResultsOverall, 49% reported solid fuel use and 26% smoked regularly. Long-term solid fuel use for cooking and current smoking were associated with higher risks of CLD deaths, with adjusted HRs of 1.26 (95% CI, 1.02–1.56) and 1.28 (1.13–1.44), respectively. Compared with never-smoking clean fuel users, the HRs were 1.41 (1.10–1.82) in never-smoking solid fuel users, 1.55 (1.17–2.06) in regular-smoking clean fuel users and 1.71 (1.32–2.20) in regular-smoking solid fuels users. Individuals who had switched from solid to clean fuels (1.07, 0.90–1.29; for median 14 years) and ex-regular smokers who stopped for non-medical reasons (1.16, 0.95–1.43; for median 10 years) had no evidence of excess risk of CLD deaths compared with clean fuel users and never-regular smokers, respectively.ConclusionsAmong Chinese adults, long-term solid fuel use for cooking and smoking were each independently associated with higher risks of CLD deaths. Individuals who had stopped using solid fuels or smoking had lower risks.
Highlights
IntroductionOver 800 million individuals worldwide are affected by chronic liver diseases (CLD), including liver cirrhosis and liver cancer, with about one-third living in China.[1,2] Hepatitis B and C infections have been the main risk factors for CLD in China, but successful hepatitis B vaccination campaigns in recent decades and lifestyle changes have prompted research into other modifiable risk factors.[3,4]Smoking has been associated with higher risks of liver disease[5,6,7] and more rapid progression of liver cirrhosis or cancer.[8,9] Fine particulate matter (PM2.5) and toxic organic and inorganic chemicals found in tobacco smoke enter the systemic circulation[10,11] and are metabolized in the liver, causing chronic hepatic damage.[12]Recently several studies have suggested that exposure to air pollutants could cause liver injury[12,13,14,15] and increased risks of liver disease.[16,17,18] Domestic burning of solid fuels (e.g. coal and biomass) for cooking is widely practised by half of the world’s population, and results in high levels of PM2.5 and carcinogens in the household environment.[19]
43.3 (Reference) aRates were weighted by group-specific hazard ratios. bHazard ratios were stratified by age-at-risk, sex and study area and adjusted for education, household income, alcohol consumption, smoking status, longterm cooking and heating fuel exposures, cooking stove ventilation, body mass index, prevalent diabetes, hepatitis B virus surface antigen status and length of recall period, where appropriate
The adjusted hazard ratios (HRs) (1.31, 0.88–1.95) associated with solid fuel use remained consistent after excluding the study areas with insufficient number of cases, the 95%confidence intervals (CIs) included the null. This large prospective study demonstrated that long-term solid fuel use for cooking and smoking were each independently associated with higher risks of chronic liver disease (CLD) mortality
Summary
Over 800 million individuals worldwide are affected by chronic liver diseases (CLD), including liver cirrhosis and liver cancer, with about one-third living in China.[1,2] Hepatitis B and C infections have been the main risk factors for CLD in China, but successful hepatitis B vaccination campaigns in recent decades and lifestyle changes have prompted research into other modifiable risk factors.[3,4]Smoking has been associated with higher risks of liver disease[5,6,7] and more rapid progression of liver cirrhosis or cancer.[8,9] Fine particulate matter (PM2.5) and toxic organic and inorganic chemicals found in tobacco smoke enter the systemic circulation[10,11] and are metabolized in the liver, causing chronic hepatic damage.[12]Recently several studies have suggested that exposure to air pollutants could cause liver injury[12,13,14,15] and increased risks of liver disease.[16,17,18] Domestic burning of solid fuels (e.g. coal and biomass) for cooking is widely practised by half of the world’s population, and results in high levels of PM2.5 and carcinogens in the household environment.[19]. Smoking has been associated with higher risks of liver disease[5,6,7] and more rapid progression of liver cirrhosis or cancer.[8,9] Fine particulate matter (PM2.5) and toxic organic and inorganic chemicals found in tobacco smoke enter the systemic circulation[10,11] and are metabolized in the liver, causing chronic hepatic damage.[12]. Multivariable Cox regression yielded adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the individual associations of self-reported long-term cooking fuel and tobacco use with major CLD death. Long-term solid fuel use for cooking and current smoking were associated with higher risks of CLD deaths, with adjusted HRs of 1.26 (95% CI, 1.02–1.56) and 1.28 (1.13–1.44), respectively
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