Solid Fuel, Secondhand Smoke, and Lung Cancer Mortality: A Prospective Cohort of 323,794 Chinese Never-Smokers

Burden of respiratory tract cancers in China and its provinces, 1990-2021: a systematic analysis of the Global Burden of Disease Study 2021

Background

Respiratory tract cancers emerged as a public health challenge with the highest incidence and mortality among all cancer types in China, despite many national policies in place, such as early cancer screening. It is of outmost importance to monitor the burden of respiratory tract cancers across China and its provinces for refining health strategies.

Methods

Based on Global Burden of Disease (GBD) estimates, the present study investigated the age-sex specific pattern alterations of incidence, prevalence, mortality, and disability adjusted life years (DALYs) of respiratory tract cancers in China from 1990 to 2021, as well as its Estimated Annual Percentage Change (EAPC), Age-Standardized Incidence Rate (ASIR), and Age-Standardized Mortality Rate (ASMR).

Findings

Between 1990 and 2021, China experienced an escalation in burdens of respiratory tract cancers, with the new cases surging from 274,752 (95% Uncertainty Interval (UI): 234,741-315,112) to 934,704 (750,040-1,136,938), marking an increase of 240.20% (156.05-342.29). Their attributed deaths similarly increased from 278,235 (238,518-322,013) to 814,121 (652,231-994,858). In 2021, the eastern and northeastern regions reported the highest incidence and mortality rates, particularly Shandong, with the highest new cases at 77,225 (58,842-101,352), while Tibet, Qinghai, and Macau observed the lowest. Regarding laryngeal cancer, Guangdong reported the highest incidence at 3466 (2230-4934), with Hainan exhibiting the highest ASIR at 3.46 (2.10-5.11) per 100,000 person-years and ASMR at 2.11 (1.37-3.09) per 100,000 person-years. Over the same timeframe, the EAPC for the ASIR of tracheal, bronchus, and lung cancer was 0.88 (0.63-1.14), and for ASMR, it was 0.29 (0.05-0.62), signifying an upward trend. Conversely, laryngeal cancer exhibited a stable ASIR with an EAPC of 0.04 (-0.22 to 0.30) and a declining ASMR with an EAPC of -1.69 (-1.80 to 1.59). Tracheal, bronchus, and lung cancer burdens exhibited notable sex differences, with their ASIR being 62.63 (46.50-79.90) per 100,000 person-years in males and 28.16 (22.22-34.90) per 100,000 person-years in females. For laryngeal cancer, the ASIR was 3.12 (2.34-4.04) per 100,000 person-years for males and 0.58 (0.35-0.79) per 100,000 person-years for females. Smoking and air pollution emerged as the predominant risk factors contributed to tracheal, bronchus, and lung cancer, accounting for 61.58% (30.00-82.95) and 25.98% (16.94-35.00) of deaths, respectively. In contrast, smoking contributed more to laryngeal cancer-caused deaths (76.70% [65.55-85.15]), followed by alcohol use (14.52% [7.70-20.99]).

Interpretation

The burden of respiratory tract cancers in China has increased over the past three decades, and without intervention, the associated health losses could escalate further. This burden predominantly affected the eastern provinces, particularly impacting older males. Our findings advocate for the formulation of targeted prevention, screening, and intervention strategies based on regional and sex disparities.

Funding

Bill & Melinda Gates Foundation.

Exposure to major coronary heart disease events reduces lung cancer risk: a mendelian randomization study based on a European population

OBJECTIVE

This study seeks to elucidate the causal relationship between major coronary heart disease events (MCHDE) and lung cancer incidence through mendelian randomization (MR), with the goal of providing evidence to inform more effective lung cancer screening and prevention strategies.

METHODS

Utilizing data from the IEU OpenGWAS project and FinnGen, this study employed a two-sample MR approach, with genetic variants serving as instrumental variables. Relevant single nucleotide polymorphisms (SNPs) associated with MCHDE and lung cancer were carefully selected, with particular attention given to mitigating potential confounders, such as smoking behaviors and statin use.

RESULTS

The MR analysis, utilizing FinnGen's MCHDE as the exposure factor, revealed a significant reduction in the incidence of non-small cell lung cancer (NSCLC) [odds ratio (OR) 0.893, 95% confidence interval (CI) 0.800-0.998] and small cell lung cancer (SCLC) [OR 0.684, 95% CI 0.500-0.936], highlighting the protective effect of MCHDE against these cancer subtypes. However, this protective effect was not observed for other types of lung cancer. Furthermore, substituting FinnGen's MCHDE with that from IEU OpenGWAS did not yield similar protective effects across various lung cancer subtypes.

CONCLUSIONS

This study suggests that MCHDE reduce the risk of NSCLC in the U.K. population and SCLC in the Finnish population. However, given that the underlying mechanism through which MCHDE reduces the risk of NSCLC and SCLC remains unclear, it is premature to conclude that individuals exposed to MCHDE do not require lung cancer screening.

Exposure to PM2.5 and its constituents in relation to thyroid function of pregnant women: Separate and mixture analyses

The relationships between exposure to PM2.5 and its constituents and thyroid hormone (TH) levels in pregnant women are still uncertain, particularly regarding the impact of mixed exposure to PM2.5 constituents on thyroid function during pregnancy. This study aimed to investigate the individual and mixed effect of PM2.5 and its constituents on TH levels during pregnancy. Fluorescence and chemiluminescence immunoassays were utilized to measure serum concentrations of free thyroxine (FT4) and thyroid-stimulating hormone (TSH) in pregnant women participating in the Fujian Birth Cohort Study (FJBCS). PM2.5 and its constituents were obtained from the ChinaHighAirPollutants dataset. Generalized linear regression model and mixture analysis were applied to explore the individual and mixed effect of PM2.5 and its constituents on TH levels. 13711 participants from the FJBCS were taken into the final analysis. In the context of separate exposure, an increase of one interquartile range (IQR) in PM2.5 exposure during the 1st trimester, 2nd trimester, and entire pregnancy was associated with a decrease of -0.042 (-0.050, -0.034), -0.017 (-0.026, -0.009), and -0.011 (-0.017, -0.004) in FT4 level, respectively. As well, significant negative associations were observed between FT4 level and PM2.5 constituents. Additionally, PM2.5 and its constituents were in relation to an increased risk of hypothyroxinemia in pregnant women. It is noteworthy that, in the context of mixed exposure, the weighted quantile sum regression (WQS) indices were significantly associated with both FT4 level (1st trimester: -0.031 (-0.036, -0.026); 2nd trimester: -0.026 (-0.030, -0.023); whole pregnancy: -0.024 (-0.028, -0.020)) and hypothyroxinemia risk (1st trimester: 1.552 (1.312, 1.821); 2nd trimester: 1.453 (1.194, 1.691); whole pregnancy: 1.402 (1.152, 1.713)). PM2.5 and its chemical constituents may affect thyroid function in pregnant women individually and in combination, with the effect observed during early gestational exposure being most pronounced.

Association between household solid fuel usage and trajectories of multimorbidity among middle-aged and older adults: a nationwide population-based cohort study

Background

This study aimed to explore the effect of household solid fuel usage on the multimorbidity trajectories among middle-aged and older adults.

Methods

Based on the 2011-2018 China Health and Retirement Longitudinal Study, the group-based trajectory modeling and the multinomial logistic regression model were used to explore the relationship between multimorbidity trajectories of older adults with different fuel types, duration of solid fuel usage, and potential interaction with PM2.5. Three multimorbidity trajectory patterns were identified by group-based trajectory modeling and labeled as "non-chronic morbidity" (no disease increase), "newly developing multimorbidity" (diseases grew from 0 to 2), and "multi-chronic multimorbidity" (diseases grew from 2 to 4).

Results

Compared to "Non-chronic morbidity," solid fuel was significantly associated with adverse multimorbidity trajectories, with an odds ratio (OR) and 95% confidence interval (CI) of 1.33 (1.11, 1.60) and 1.35 (1.18, 1.55) for newly developing and multi-chronic group, respectively. An adverse multimorbidity trajectory tended to be established with longer durations of solid fuel usage than "Non-chronic morbidity." For "Newly-developing multimorbidity," the ORs (95% CI) for 1-7 years and ≥ 8 years of solid fuel usage were 1.16 (0.94, 1.42) and 1.41 (1.12, 1.76), respectively, with P trend=0.001, while in "Multi-chronic multimorbidity," those were 1.25 (1.07, 1.47) and 1.68 (1.41, 2.00), respectively, with P trend <0.001. In the interaction analysis, the association between solid fuel usage and trajectories was significant only in areas where PM2.5 was lower than 50 μg/m3.

Conclusion

For the middle-aged and older Chinese population, a higher risk of multimorbidity trajectory is associated with household solid fuel usage, especially in the areas with lower PM2.5.

Switching indoor fuels and the incidence of physical-psychological-cognitive multimorbidity: A prospective cohort study

BACKGROUND

In developing countries, including China, solid-fuel-based heating and cooking is common. For older people, the multimorbidity prevalence is exceptionally high. Nevertheless, studies on the associations of indoor solid fuels use, especially switching fuels types, on multimorbidity in middle-aged and older people is scarce.

METHODS

Data from five waves of the China Health and Retirement Longitudinal Study were used in this study. Indoor fuels were classified as solid or clean fuels. Physical-psychological-cognitive multimorbidity (PPC-multimorbidity) was defined as the simultaneous presence of three disease types (physical illness, psychological disorders, cognitive impairment). Using Cox proportional risk models, hazard ratios (HRs) and 95 % confidence intervals (95 % CI) were calculated to investigate the associations of heating- and cooking-related baseline indoor fuels and switching indoor fuels with PPC-multimorbidity incidence.

RESULTS

In the heating (n=3121, mean age=56.55 years, male proportion=54.25 %) and cooking (n=3574, mean age=56.67 years, male proportion=52.94 %) analyses, 75.07 % and 45.64 % of the participants used solid fuels at baseline, and 564 (18.07 %) and 613 (17.15 %) PPC-multimorbidity cases were diagnosed during follow-up, respectively. Participants with baseline heating- and cooking-based solid fuels use had greater PPC-multimorbidity incidences [HRs (95 % CIs): 1.23 (0.98, 1.55) and 1.44 (1.21, 1.73)], respectively. Additionally, combined baseline heating- and cooking-based solid fuels use was associated with even greater PPC-multimorbidity incidence [HR (95 % CI): 1.55 (1.18, 2.04)]. Persistent solid fuels use obviously increased the PPC-multimorbidity incidence [HRs (95 % CIs): 2.43 (1.67, 3.55) for heating and 2.63 (2.03, 3.40) for cooking]. Moreover, switching from solid to clean fuels was associated with a significantly decreased PPC-multimorbidity incidence [HRs (95 % CIs): 0.27 (0.20, 0.35) for heating and 0.36 (0.28, 0.46) for cooking].

CONCLUSIONS

Long-term solid-fuels use is associated with an increased PPC-multimorbidity incidence, and switching to cleaner fuels is associated with a decreased PPC-multimorbidity incidence in adults aged ≥45 years.

Reproductive factors and risk of lung cancer among 300,000 Chinese female never-smokers: evidence from the China Kadoorie Biobank study

BACKGROUND

Lung cancer is the leading cause of cancer mortality among Chinese females despite the low smoking prevalence among this population. This study assessed the roles of reproductive factors in lung cancer development among Chinese female never-smokers.

METHODS

The prospective China Kadoorie Biobank (CKB) recruited over 0.5 million Chinese adults (0.3 million females) from 10 geographical areas in China in 2004-2008 when information on socio-demographic/lifestyle/environmental factors, physical measurements, medical history, and reproductive history collected through interviewer-administered questionnaires. Cox proportional hazard regression was used to estimate adjusted hazard ratios (HRs) of lung cancer by reproductive factors. Subgroup analyses by menopausal status, birth year, and geographical region were performed.

RESULTS

During a median follow-up of 11 years, 2,284 incident lung cancers occurred among 282,558 female never-smokers. Ever oral contraceptive use was associated with a higher risk of lung cancer (HR = 1.16, 95% CI: 1.02-1.33) with a significant increasing trend associated with longer duration of use (p-trend = 0.03). Longer average breastfeeding duration per child was associated with a decreased risk (0.86, 0.78-0.95) for > 12 months compared with those who breastfed for 7-12 months. No statistically significant association was detected between other reproductive factors and lung cancer risk.

CONCLUSION

Oral contraceptive use was associated with an increased risk of lung cancer in Chinese female never-smokers. Further studies are needed to assess lung cancer risk related to different types of oral contraceptives in similar populations.

Health effects associated with exposure to secondhand smoke: a Burden of Proof study

Despite a gradual decline in smoking rates over time, exposure to secondhand smoke (SHS) continues to cause harm to nonsmokers, who are disproportionately children and women living in low- and middle-income countries. We comprehensively reviewed the literature published by July 2022 concerning the adverse impacts of SHS exposure on nine health outcomes. Following, we quantified each exposure-response association accounting for various sources of uncertainty and evaluated the strength of the evidence supporting our analyses using the Burden of Proof Risk Function methodology. We found all nine health outcomes to be associated with SHS exposure. We conservatively estimated that SHS increases the risk of ischemic heart disease, stroke, type 2 diabetes and lung cancer by at least around 8%, 5%, 1% and 1%, respectively, with the evidence supporting these harmful associations rated as weak (two stars). The evidence supporting the harmful associations between SHS and otitis media, asthma, lower respiratory infections, breast cancer and chronic obstructive pulmonary disease was weaker (one star). Despite the weak underlying evidence for these associations, our results reinforce the harmful effects of SHS on health and the need to prioritize advancing efforts to reduce active and passive smoking through a combination of public health policies and education initiatives.

Household air pollution and risk of incident lung cancer in urban China: A prospective cohort study

Household air pollution (HAP) is associated with the development of lung cancer, yet few studies investigated the exposure patterns and joint associations with tobacco smoking. In our study, we included 224 189 urban participants from China Kadoorie Biobank (CKB), 3288 of which diagnosed with lung cancer during the follow-up. Exposure to four HAP sources (solid fuels for cooking/heating/stove and environmental tobacco smoke exposure) was assessed at baseline. Distinct HAP patterns and their associations with lung cancer were examined through latent class analysis (LCA) and multivariable Cox regression. A total of 76.1% of the participants reported regular cooking and 52.2% reported winter heating, of which 9% and 24.7% used solid fuels, respectively. Solid fuel heating increased lung cancer risk (Hazards ratio [HR]: 1.25, 95% confidence interval [CI]: 1.08-1.46). LCA identified three HAP patterns; the "clean fuel cooking and solid fuel heating" pattern significantly increased lung cancer risk (HR: 1.25, 95% CI: 1.10-1.41), compared to low HAP pattern. An additive interaction was observed between heavy smoking and "clean fuel cooking and solid fuel heating" (relative excess risk [RERI]: 1.32, 95% CI: 0.29-2.47, attributable proportion [AP]: 0.23, 95% CI: 0.06-0.36). Cases resulting from solid fuel account for ~4% of total cases (population attribute fraction [PAF]overall : 4.31%, 95% CI: 2.16%-6.47%, PAFever smokers : 4.38%, 95% CI: 1.54%-7.23%). Our results suggest that in urban China, solid fuel heating increased the risk of lung cancer, particularly among heavy smokers. The whole population could benefit from cleaner indoor air quality by reducing using solid fuels, especially smokers.

Self-Reported Primary Cooking Fuels Use and Risk of Chronic Digestive Diseases: A Prospective Cohort Study of 0.5 Million Chinese Adults

BACKGROUND

Household air pollution (HAP) from inefficient combustion of solid fuels is a major health concern worldwide. However, prospective evidence on the health impacts of solid cooking fuels and risks of chronic digestive diseases remains scarce.

OBJECTIVES

We explored the effects of self-reported primary cooking fuels on the incidence of chronic digestive diseases.

METHODS

The China Kadoorie Biobank recruited 512,726 participants 30-79 years of age from 10 regions across China. Information on primary cooking fuels at the current and previous two residences was collected via self-reporting at baseline. Incidence of chronic digestive diseases was identified through electronic linkage and active follow-up. Cox proportional hazards regression models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations of self-reported long-term cooking fuel patterns and weighted duration of self-reported solid cooking fuel use with chronic digestive diseases incidence. Linear trend was tested by assigning the medians of weighted duration in each group and then taking those as continuous variables in the models. Subgroup analyses were undertaken across the baseline characteristics of participants.

RESULTS

During 9.1 ± 1.6 y of follow-up, 16,810 new cases of chronic digestive diseases were documented, among which 6,460 were diagnosed as cancers. Compared with long-term cleaner fuel use, self-reported long-term use of solid cooking fuels (i.e., coal, wood) was associated with elevated risks of chronic digestive diseases (HR = 1.08 ; 95% CI: 1.02, 1.13), including nonalcoholic fatty liver disease (NAFLD) (HR = 1.43 ; 95% CI: 1.10, 1.87), hepatic fibrosis/cirrhosis (HR = 1.35 ; 95% CI: 1.05, 1.73), cholecystitis (HR = 1.19 ; 95% CI: 1.07, 1.32), and peptic ulcers (HR = 1.15 ; 95% CI: 1.00, 1.33). The longer the weighted duration of self-reported solid cooking fuel use, the higher the risks of chronic digestive diseases, hepatic fibrosis/cirrhosis, peptic ulcers, and esophageal cancer (p Trend < 0.05 ). The aforementioned associations were modified by sex and body mass index (BMI). Positive associations of always solid cooking fuel use with chronic digestive disease, hepatic fibrosis/cirrhosis, NAFLD, and cholecystitis were observed among women but not men. The longer the weighted duration of self-reported solid cooking fuel use, the higher the risk of NAFLD among those with a BMI ≥ 28   kg / m 2 .

DISCUSSION

Long-term self-reported solid cooking fuels use was associated with higher risks of chronic digestive diseases. The positive association of HAP from solid cooking fuels with chronic digestive diseases indicates for an imminent promotion of cleaner fuels as public health interventions. https://doi.org/10.1289/EHP10486.

Female reproductive and hormonal factors and lung cancer mortality among never-smokers: A prospective cohort study of 287 408 Chinese women

There is growing, but inconsistent evidence suggesting oestrogen may play a key role in lung cancer development, especially among never-smoking women for whom lung cancer risk factors remain largely elusive. Using the China Kadoorie Biobank, a large-scale prospective cohort with 302 510 women aged 30 to 79 years recruited from 10 regions in China during 2004 to 2008, we assessed the risk of lung cancer death among self-reported never-smoking women who were cancer-free at baseline, in relation to age at menarche, age at menopause, time since menopause, prior use of oral contraceptives (OCP), number of livebirths, breastfeeding and age at first livebirth. Women were followed up to December 31, 2016 with linkage to mortality data. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox regression, adjusting for key confounders including several socio-demographic, environmental and lifestyle factors. Among 287 408 never-smoking women, 814 died from lung cancer with a median follow-up of 10.3 years. Women who had used OCP within 15 years prior to baseline had a significantly higher hazard of lung cancer death compared with never-users: HR = 1.85 (95% CI: 1.14-3.00) and risk increased by 6% with each additional year of use: HR = 1.06 (1.01-1.10). Among parous women, the hazard of lung cancer death increased by 13% with each single livebirth: HR = 1.13 (1.05-1.23); and among post-menopausal women, the risk increased by 2% with each year since menopause: HR = 1.02 (1.01-1.04). These results suggest that reproductive factors which were proxies for lower endogenous oestrogen level, for example, longer duration of OCP use, could play a role in lung cancer development.

Risk-stratified Approach for Never- and Ever-Smokers in Lung Cancer Screening: A Prospective Cohort Study in China

Rationale: Over 40% of lung cancer cases occurred in never-smokers in China. However, high-risk never-smokers were precluded from benefiting from lung cancer screening as most screening guidelines did not consider them. Objectives: We sought to develop and validate prediction models for 3-year lung cancer risks for never- and ever-smokers, named the China National Cancer Center Lung Cancer models (China NCC-LC_m2021 models). Methods: 425,626 never-smokers and 128,952 ever-smokers from the National Lung Cancer Screening program were used as the training cohort and analyzed using multivariable Cox models. Models were validated in two independent prospective cohorts: one included 369,650 never-smokers and 107,678 ever-smokers (841 and 421 lung cancers), and the other included 286,327 never-smokers and 78,469 ever-smokers (503 and 127 lung cancers). Measurements and Main Results: The areas under the receiver operating characteristic curves in the two validation cohorts were 0.698 and 0.673 for never-smokers and 0.728 and 0.752 for ever-smokers. Our models had higher areas under the receiver operating characteristic curves than other existing models and were well calibrated in the validation cohort. The China NCC-LC_m2021 ⩾0.47% threshold was suggested for never-smokers and ⩾0.51% for ever-smokers. Moreover, we provided a range of threshold options with corresponding expected screening outcomes, screening targets, and screening efficiency. Conclusion: The construction of the China NCC-LC_m2021 models can accurately reflect individual risk of lung cancer, regardless of smoking status. Our models can significantly increase the feasibility of conducting centralized lung cancer screening programs because we provide justified thresholds to define the high-risk population of lung cancer and threshold options to adapt different configurations of medical resources.

Short-Term Effects of Side-Stream Smoke on Nerve Growth Factor and Its Receptors TrKA and p75NTR in a Group of Non-Smokers

Environmental tobacco smoke remains a major risk factor, for both smokers and non-smokers, able to trigger the initiation and/or the progression of several human diseases. Although in recent times governments have acted with the aim of banning or strongly reducing its impact within public places and common spaces, environmental tobacco smoke remains a major pollutant in private places, such as the home environment or cars. Several inflammatory and long-term biomarkers have been analysed and well-described, but the list of mediators modulated during the early phases of inhalation of environmental tobacco smoke needs to be expanded. The aim of this study was to measure the short-term effects after exposure to side-stream smoke on Nerve Growth Factor and its receptors Tropomyosin-related kinase A and neurotrophin p75, molecules already described in health conditions and respiratory diseases. Twenty-one non-smokers were exposed to a home-standardized level of SS as well as to control smoke-free air. Nerve Growth Factor and inflammatory cytokines levels, as well the expression of Tropomyosin-related kinase A and neurotrophin receptor p75, were analysed in white blood cells. The present study demonstrates that during early phases, side-stream smoke exposure induced increases in the percentage of neurotrophin receptor p75-positive white blood cells, in their mean fluorescent intensity, and in gene expression. In addition, we found a positive correlation between the urine cotinine level and the percentage of neurotrophin receptor-positive white blood cells. For the first time, the evidence that short-term exposure to side-stream smoke is able to increase neurotrophin receptor p75 expression confirms the very early involvement of this receptor, not only among active smokers but also among non-smokers exposed to SS. Furthermore, the correlation between cotinine levels in urine and the increase in neurotrophin receptor p75-positive white blood cells could represent a potential novel molecule to be investigated for the detection of SS exposure at early time points.