Standardized Mortality Ratio For Lung Cancer Research Articles

Updated Analysis of Radon Exposure and Lung Cancer Mortality in the Cohort of Newfoundland Fluorspar Miners (1950-2016).

The commercial mining of fluorspar in St. Lawrence Newfoundland began in 1933. Miners who worked underground were exposed to high levels of radon progeny, especially before ventilation was introduced into the mines in 1960. The mean cumulative radon exposure for underground miners in this cohort was 380.9 working level months (WLM). A series of studies of this cohort have characterized the increased risks of lung cancer mortality due to radon. We have extended the follow-up of this cohort an additional 15 years to provide additional insights on the risks of low levels of radon exposure, and the modifying effects of time since exposure, age at first exposure, attained age, duration of exposure, and cigarette smoking. The cohort consisted of 1,735 underground and 315 male surface miners who, combined, accrued 81,650 person-years of follow-up. The mortality experience of the cohort was determined from 1950-2016 through record linkage to Canadian national death data. Individual-level estimates of exposure to radon progeny, in WLMs, were determined for each year of employment. We compared the mortality experience of the underground miners to Newfoundland men using the standardized mortality ratio (SMR). Poisson regression models were fit to estimate excess relative risks (ERR) per 100 WLM. There were 236 lung cancer deaths identified, and of these, 221 occurred among underground workers. The SMR for lung cancer among underground miners compared to Newfoundland men was 2.67 (95% CI: 2.33, 3.04). The ERR per 100 WLM for lung cancer mortality, assuming a 5-year exposure lag, was 0.41 (95% CI: 0.23, 0.59). Attained age and time since exposure were important modifiers to the radon-lung cancer relationship. The joint relationship between smoking and radon on lung cancer risk was sub-additive, however, the smoking data were limited and available for only half of the cohort.

Mortality for Lung Cancer among PVC Baggers Employed in the Vinyl Chloride Industry.

Vinyl-chloride monomer (VCM) is classified as a known carcinogen of the liver; for lung cancer, some results suggest a potential association with polyvinyl chloride (PVC) dust. We evaluated the relationship between lung cancer mortality and exposure as PVC baggers in a cohort of workers involved in VCM production and polymerization in Porto Marghera (Venice, Italy) considering both employment status and smoking habits. The workers were studied between 1973 and 2017. A subset of them (848 over 1658) was interviewed in the 2000s to collect information about smoking habits and alcohol consumption. Missing values were imputed by the Multivariate Imputation by Chained Equations (MICE) algorithm. We calculated standardized mortality ratios (SMR) and 95% confidence intervals (95% CIs) using regional reference rates by task (never, ever, and exclusively baggers) and by smoking habits. Mortality rate ratios (MRR), adjusted for age, calendar time, time since first exposure, and smoking habits, were obtained via Poisson regression using Rubin’s rule to combine results from imputed datasets calculating the fraction of information due to non-response. Lung cancer mortality was lower than the regional reference in the whole cohort (lung cancer SMR = 0.92; 95% CI 0.75–1.11). PVC baggers showed a 50% increase in lung cancer mortality compared to regional rates (SMR = 1.48; 95% CI 0.82–2.68). In the cohort analyses, a doubled risk of lung cancer mortality among PVC baggers was confirmed after adjustment for smoking and time-dependent covariates (MRR = 1.99, 95% CI 1.04–3.81). Exposure to PVC dust resulting from activity as bagger in a polymerization PVC plant was associated with an increase in lung cancer mortality risk after adjustment for smoking habits.

L'impatto dell'esposizione occupazionale ad amianto sul tumore del polmone in Italia.

to perform a meta-analysis of cohort studies on lung cancer mortality in occupational sectors exposed to asbestos, particularly in the construction sector, and to use data from Italian cohorts exposed to asbestos to estimate the number of lung cancer cases attributable to asbestos in Italy. systematic literature review and estimation of lung cancer deaths and cases attributable to asbestos in Italian cohorts and from the Italian National Register of Malignant Mesothelioma (ReNaM). the literature search was conducted in Medline and Embase (Ovid), including papers published from 1999 to May 2019. The following sectors were considered most exposed to asbestos: asbestos-cement, rolling-stock, shipyards, dockyards, glass workers, insulators, asphalt roll production workers, industrial ovens, miners. Moreover, the construction sector was included. the standardized mortality ratio (SMR) was estimated from the meta-analysis of the literature review. The ratio lung cancer to mesothelioma attributable cases was estimated by occupational sector from the Italian cohorts. For the construction sector, the ratio lung cancer to mesothelioma cases was estimated within the exposed workers estimated by CAREX (1990-1993). The ratios were applied to the mesothelioma cases registered at the ReNaM for the 2010-2015 period, to obtain a national estimate of lung cancer cases attributable to occupational exposure to asbestos. the meta-analytical SMR for lung cancer in men varied between 1.05 (asphalt roll) and 2.36 (insulation). The mean risk for all sectors was 1.37 in men and 1.60 in women. It increased in cohorts with latency higher than 20 years. Significant risks were observed in asbestos-cement (both genders), construction, and mining sectors. There was a mean of 1.1, 2.7, and 2.8 lung cancer deaths per mesothelioma death in the cement-asbestos, harbour, and construction sectors, respectively. The impact in terms of lung cancer cases estimated at the national level was equal to 3,814 cases between 2010 and 2015. to provide an overall assessment of the impact of the occupational asbestos exposure, it is important to consider lung cancer cases, in addition to malignant mesotheliomas. This study was able to estimate the impact of asbestos on lung cancer in Italy 25 years after the ban of this occupational carcinogen, with the largest contribution in terms of attributable cases coming from the construction sector. It is urgent to implement adequate information and prevention strategies, health surveillance of workers, and the appropriate legal framework for insurance purposes.

Colorectal cancer and asbestos exposure-an overview.

The relationship between colorectal cancer and asbestos exposure has not been fully clarified. This study aimed to determine the associations between asbestos exposure and colorectal cancer. We performed a meta-analysis to quantitatively evaluate this association. A fixed effects model was used to summarize the relative risks across studies. Sources of heterogeneity were explored through subgroup analyses and meta-regression. We analyzed the dose-effect relationship using lung cancer standardized mortality ratio (SMR) and the risk of mesothelioma as a percent (%) as exposure surrogates. A total of 47 cohort studies were included. We identified 28 incidence cohort studies from 17 separate papers and extracted colorectal cancer standardized incidence ratio (SIR). Cancer mortality data were extracted from 19 separate cohorts among 13 papers. The overall colorectal cancer SMR for synthesis cohort was 1.07 (95% CI 1.02–1.12). Statistically significant excesses were observed in exposure to mixed asbestos (SMR/SIR=1.07), exposure to production (SMR/SIR=1.11), among asbestos cement workers (SMR/SIR=1.18) and asbestos textile workers (SMR/SIR=1.11). Additionally, we determined that the SMR for lung cancer increased with increased exposure to asbestos, as did the risk for colorectal cancer. This study confirms that colorectal cancer has a positive weak associations with asbestos exposure.

Mortality for Mesothelioma and Lung Cancer in a Cohort of Asbestos Cement Workers in BARI (Italy): Time Related Aspects of Exposure.

In this cohort mortality study we used an exposure index to evaluate individual cumulative exposure as proxy of asbestos dose and we evaluated change in cancer mortality pattern after long time since the end of exposure. We calculated standardized mortality ratios (SMRs) for several causes of death stratified by latency, cumulative exposure, and time since last exposure (TSLE). Latency: we observed a peak and then a decrease in SMR for lung, pleural, and peritoneal cancer. Cumulative Exposure: We observed a peak and then a decrease in SMR for lung and pleural cancer, not for peritoneal cancer. TSLE: Pleural cancer SMR peaked at 20 to 29 years, then decreased, peritoneal cancer SMR reached a plateau after 20 years and lung cancer mortality was in excess in each class. We found different patterns in mortality in the main asbestos-related tumors.

Cancer incidence and mortality associated with non-occupational and low dose exposure to Libby vermiculite in Minnesota

BackgroundA vermiculite processing plant in a Minneapolis, Minnesota neighborhood utilized asbestos-containing ore from Libby, Montana from the late 1930's until 1989. Multiple pathways of exposure to Libby asbestos were characterized in a cohort of over 6000 plant workers and residents living near the plant. ObjectiveWe conducted a cohort linkage study to assess the impact of cumulative low dose exposure and the role of occupational history on asbestos-related mortality and cancer morbidity among cohort members residing near a vermiculite plant. MethodsCohort members alive in 1988 (n = 5848) were linked to the Minnesota Cancer Surveillance System to identify incident cases of mesothelioma, lung cancer, and all-cancer diagnosed from 1988 to 2010. Proportional incidence ratios (PIRs) were calculated for mesothelioma and lung cancer. Vital status and cause of death were ascertained from Minnesota vital records and the National Death Index (1988–2011). Mortality rates of the cohort (2001–2011) for asbestos-related outcomes were compared to the Minnesota population to estimate standardized mortality ratios (SMRs) and stratified by gender, exposure, and occupational history categories. ResultsWe identified seven cases of mesothelioma, with elevated incidence only in females (PIR = 11.76, 95% CI: 3.17, 30.12). Lung cancer was elevated in both genders: PIR = 1.54 (95% CI: 1.19, 2.0) in males and 1.62 (95% CI: 1.21, 2.12) in females. We found elevated mortality from COPD, lung cancer, and mesothelioma among females (SMR for mesothelioma in females = 18.97, CI: 3.91, 55.45), among the 546 deaths identified. All four deaths from mesothelioma occurred in the >75th percentile of exposure (>0.0156 fiber/cc x months). The SMR for lung cancer and all respiratory cancer was elevated even after controlling for occupation. ConclusionsCommunity exposure to Libby amphibole asbestos from a vermiculite processing plant is associated with increased risk of COPD, lung cancer and mesothelioma incidence and mortality, most notably among females, and is likely to remain a public health issue for years to come.

Follow-up of the cohort of workers exposed to arsenic in the Manfredonia petrochemical plant (Apulia Region, Southern Italy)

in 1976, a major chemical accident occurred in Manfredonia (Apulia Region, Southern Italy) due to an explosion in the fertilizer area. More than 10 tons of arsenic were released into the atmosphere, contaminating the plant and the surrounding areas. At the end of the 90s, criminal proceedings were initiated and a cohort study was conducted within the trial. to update the vital status of workers enrolled within the trial; some relevant results are also given. two different approaches were used to update the vital status depending on the residence of the individuals in the cohort. We computed cause-specific standardised mortality ratios (SMRs), stratified according to the type of employment (urea sector, caprolactam sector, and contract workers), with 95% confidence intervals (95%CI). For internal comparison purpose, Cox regression models were used and hazard ratios (HRs) were calculated, considering workers from the caprolactam area as a reference category. the cohort consisted of 1,467 workers; 114 were dead at the end of the previous follow-up. Among 728 workers residing in Manfredonia, we identified 619 people still alive and 93 deceased. Among 625 not-residents, 508 were alive and 93 deceased. For 285 cases out of 306, cause of death was ascertained. Contract workers show a statistically significant SMR for lung cancer (SMR: 1.26; 95%CI 1.05-1.54) and an increased risk for overall mortality (HR: 2.3; 95%CI 1.1-4.9). Workers residing in Manfredonia show a higher risk of lung cancer mortality in comparison to not-residents (HR: 2.3; 95%CI 1.1-4.9). workers who were most exposed to arsenic during the site cleaning show an increased risk of overall mortality compared to the least exposed and an increased risk of lung cancer compared to the general population.

Age at Exposure to Arsenic in Water and Mortality 30-40 Years After Exposure Cessation.

Arsenic in drinking water is known to cause cancer and noncancer diseases, but little is known about its association with age at exposure. Here, we investigated age at arsenic exposure and mortality in Antofagasta, Chile, 30-40 years after a distinct period of very high water arsenic concentrations (1958-1970). We calculated standardized mortality ratios (SMRs) comparing Antofagasta with the rest of Chile for 2001-2010 by sex and age at potential first exposure. A remarkable relationship with age at first exposure was found for bronchiectasis, with increased risk in adults 30-40 years after exposure being confined to those who were in utero (SMR = 11.7, 95% confidence interval (CI): 4.3, 25.4) or aged 1-10 years (SMR = 5.4, 95% CI: 1.1, 15.8) during the high-exposure period. Increased SMRs for lung, bladder, and laryngeal cancer were evident for exposures starting at all ages, but the highest SMRs were for exposures beginning at birth (for bladder cancer, SMR = 16.0 (95% CI: 10.3, 23.8); for laryngeal cancer, SMR = 6.8 (95% CI: 2.2, 15.8); for lung cancer, SMR = 3.8 (95% CI: 2.9, 4.9)). These findings suggest that interventions targeting early-life arsenic exposure could have major impacts in reducing long-term mortality due to arsenic 30-40 years after exposure ends.

Study of coverage of confidence intervals for the standardized mortality ratio in studies with missing death certificates.

This paper assesses the coverage probability of commonly used confidence intervals for the standardized mortality ratio (SMR) when death certificates are missing. It also proposes alternative confidence interval approaches with coverage probabilities close to .95. In epidemiology, the SMR is an important measure of risk of disease mortality (or incidence) to compare a specific group to a reference population. The appropriate confidence interval for the SMR is crucial, especially when the SMR is close to 1.0 and the statistical significance of the risk needs to be determined. There are several ways to calculate confidence intervals, depending on a study characteristics (ie, studies with small number of deaths, studies with small counts, aggregate SMRs based on several countries or time periods, and studies with missing death certificates). This paper summarizes the most commonly used confidence intervals and newly applies several existing approaches not previously used for SMR confidence intervals. The coverage probability and length of the different confidence intervals are assessed using a simulation study and different scenarios. The performance of the confidence intervals for the lung cancer SMR and all other cancer SMR is also assessed using the dataset of French and Czech uranium miners. Finally, the most appropriate confidence intervals to use under different study scenarios are recommended.

桜島周辺地域における肺がんの標準化死亡比(SMR)と桜島火山からの降灰量との関係性に関する予察的検討

桜島周辺地域における肺がんの標準化死亡比(SMR)と桜島火山からの降灰量との関係性に関する予察的検討

A mortality study of beryllium workers.

We aimed at investigating mortality among beryllium‐exposed workers, according to solubility of beryllium and beryllium compounds. We conducted an historical cohort study of 16,115 workers employed during 1925–2008 in 15 facilities, including eight entailing exposure to insoluble beryllium and seven entailing exposure to soluble/mixed beryllium compounds, who were followed up for mortality until 2011. Data were analyzed using indirect standardization and Cox regression modeling. Lung cancer standardized mortality ratio (SMR, national reference rates) was 1.02 (95% confidence interval [CI]: 0.94–1.10) in the whole cohort, 0.88 (95% CI: 0.75–1.03) in the insoluble beryllium subcohort, and 1.09 (95% CI: 0.99–1.09) in the soluble/mixed beryllium subcohort. For lung cancer, there was an association with period of hire in soluble/mixed beryllium plants but not in insoluble plants, and, conversely, employment in soluble/mixed plants was associated with increased mortality only among workers hired before 1955. There was no trend with duration of employment. Mortality from chronic beryllium disease increased, in particular, among workers hired before 1955 in soluble/mixed beryllium facilities. There was no increase in lung cancer mortality in the entire cohort and lung cancer mortality was not increased among beryllium workers hired in 1955 or later in soluble/mixed beryllium facilities, or at any time among those employed in insoluble beryllium facilities.

Cancer co-occurrence patterns in Parkinson’s disease and multiple sclerosis—Do they mirror immune system imbalances?

BackgroundTo examine the site-specific cancer mortality among deaths registered with Parkinson’s disease (PD) and multiple sclerosis (MS). We focused on the patterns related to the most frequent cancers. MethodsWe analyzed Swiss mortality data over a 39-year period (1969–2007), using a statistical approach applicable to unique daabases, i.e. when no linkage with morbidity databases or disease registries is possible. It was based on a case-control design with bootstrapping to derive standardized mortality ratios (SMR). The cases were defined by the cancer-PD or cancer-MS co-registrations, whereas the controls were drawn from the remaining records with cancer deaths (matching criteria: sex, age, language region of Switzerland, subperiods 1969–1981, 1982–1994, 1995–2007). ResultsFor PD we found lower SMRs in lung and liver cancer and higher SMRs in melanoma/skin cancer, and in cancers of breast and prostate. As for MS, the SMR in lung cancer was lower than expected, whereas SMRs in colorectal, breast and bladder cancer were higher. ConclusionsA common pattern of associations can be observed in PD and MS, with a lower risk of lung cancer and higher risk of breast cancer than expected. Thus, PD and MS resemble other conditions with similar (schizophrenia) or reversed patterns (rheumatoid arthritis, immunosuppression after organ transplantation).

Cause-specific mortality in individuals with severe alpha 1-antitrypsin deficiency in comparison with the general population in Sweden.

BackgroundSevere alpha 1-antitrypsin deficiency (PiZZ) predisposes to morbidity and mortality due to early-onset emphysema and liver disease. The risk of death from other causes, including cardiovascular disease and cancer, has not been well investigated. We aimed to analyze cause-specific mortality in PiZZ individuals compared with the general Swedish population.MethodsData on 1,561 PiZZ individuals from the Swedish National AAT Deficiency Register, prospectively followed from 1991 to 2014, were analyzed. Causes of death according to the Swedish National Causes of Death Register for the study group were compared with those for the general Swedish population matched for age, sex, and calendar year, with the excess mortality expressed as standardized mortality ratios (SMRs) with 95% confidence intervals (CIs).ResultsThere were 524 deaths during the follow-up period. PiZZ individuals had excess all-cause mortality compared with the Swedish general population (SMR 3.6, 95% CI 3.3–3.9). SMR for ischemic heart disease (IHD) was 0.5 (95% CI 0.3–0.8) and was similar for never and ever-smokers, and in males and females. SMR for lung cancer was 0.9 (95% CI 0.4–1.7). PiZZ individuals had increased mortality compared with the general population for the following diseases: respiratory disease, SMR 48.4 (95% CI 43.0–54.5); primary liver carcinoma, SMR 90.0 (95% CI 59.3–130.9); complicated colon diverticulitis, SMR 20.8 (95% CI 6.7–48.6); and pulmonary embolism, SMR 6.9 (95% CI 3.3–12.7).ConclusionPiZZ individuals had a reduced mortality risk of IHD. Mortality due to respiratory, hepatic disease, diverticulitis, and pulmonary embolism was markedly increased compared with the age- and sex-matched Swedish population.

Mortality Trends in Crohn's Disease and Ulcerative Colitis: A Population-based Study in Québec, Canada.

Mortality rates greater than in the general population have been reported in the population with Crohn's disease (CD), but reports for ulcerative colitis (UC) are conflicting. Trends with time were rarely described. We aimed to assess whether CD and UC mortality in Québec differs from that in the general population and to describe the trends over a 10-year observation period. This is a population-based cohort study using the Québec administrative health databases and death certificates registry. All-cause and cause-specific standardized mortality ratios (SMRs) were computed for 1999 to 2008. A time trend analysis was used to assess changes in the SMR with the calendar year. All-cause mortality was significantly increased in CD and UC compared to the general population: SMR: CD 1.45 (95% confidence interval: 1.34-1.58), UC 1.21 (95% confidence interval: 1.12-1.32). In CD, mortality from digestive conditions, all neoplasms, digestive neoplasms, and colorectal, lymphatic, and lung cancer was significantly higher than in the general population. In UC, mortality from digestive, respiratory, and infectious conditions was also significantly increased. In both CD and UC, there was a decrease with time in all-cause SMRs and in digestive conditions, digestive neoplasms, colorectal cancer, and infectious diseases. SMRs for lung cancer and respiratory conditions increased over time in CD. All-cause mortality was significantly higher in CD and UC populations than in the general population. However, a decreasing trend with time was observed in all-cause and some cause-specific SMRs. In CD, SMRs for lung cancer and respiratory conditions increased during the observation period.

Residential radon and lung cancer. An ecologic study in Galicia, Spain

Background and objectiveResidential radon is the second cause of lung cancer and the first in never smokers. Galicia is a high radon emission area. The objective of this study is to analyse the relationship between municipal lung cancer mortality and residential radon in Galician municipalities. Material and methodWe performed an ecologic study including 192 municipalities with at least 3 residential radon measurements. The observed number of lung cancer deaths was obtained from the Galician Mortality Registry. Afterwards, we calculated the standardised mortality ratios (SMRs) of lung cancer for males and females for the period comprising 1980–2009. Median municipal residential radon concentrations were correlated with lung cancer SMRs. ResultsMedian residential radon concentration for the included municipalities was 75Bq/m3, with an interquartile range of 40.7–154Bq/m3. The correlation between lung cancer SMRs and municipal radon concentration was statistically significant for males (p=.023) whereas it did not reach statistical significance for females (p=.087). ConclusionThere exists an association between municipal residential radon and lung cancer mortality in Galicia for males, though for women the association is not statistically significant. These results suggest that residential radon could raise the risk of lung cancer in males, though for females no association is evident.

A mortality study of workers exposed to insoluble forms of beryllium

This study investigated lung cancer and other diseases related to insoluble beryllium compounds. A cohort of 4950 workers from four US insoluble beryllium manufacturing facilities were followed through 2009. Expected deaths were calculated using local and national rates. On the basis of local rates, all-cause mortality was significantly reduced. Mortality from lung cancer (standardized mortality ratio 96.0; 95% confidence interval 80.0, 114.3) and from nonmalignant respiratory diseases was also reduced. There were no significant trends for either cause of death according to duration of employment or time since first employment. Uterine cancer among women was the only cause of death with a significantly increased standardized mortality ratio. Five of the seven women worked in office jobs. This study confirmed the lack of an increase in mortality from lung cancer and nonmalignant respiratory diseases related to insoluble beryllium compounds.

Radón residencial y cáncer de pulmón. Un estudio ecológico en Galicia

Background and objectiveResidential radon is the second cause of lung cancer and the first in never smokers. Galicia is a high radon emission area. The objective of this study is to analyze the relationship between municipal lung cancer mortality and residential radon in Galician municipalities. Material and methodWe performed an ecologic study including 192 municipalities with at least 3 residential radon measurements. The observed number of lung cancer deaths was obtained from the Galician Mortality Registry. Afterwards, we calculated the standardized mortality ratios (SMRs) of lung cancer for males and females for the period comprising 1980-2009. Median municipal residential radon concentrations were correlated with lung cancer SMRs. ResultsMedian residential radon concentration for the included municipalities was 75Bq/m3, with an interquartile range of 40.7 to 154Bq/m3. The correlation between lung cancer SMRs and municipal radon concentration was statistically significant for males (P=.023) whereas it did not reach statistical significance for females (P=.087). ConclusionThere exists an association between municipal residential radon and lung cancer mortality in Galicia for males, though for women the association is not statistically significant. These results suggest that residential radon could raise the risk of lung cancer in males, though for females no association is evident.

Carving of non-asbestiform tremolite and the risk of lung cancer: a follow-up mortality study in a historical nephrite processing cohort

ObjectivesThe health risks associated with exposure to non-asbestiform asbestos minerals, including nephrite, are unclear. In 1965 nephrite processing began in the town of Fengtian in Taiwan, and the majority of...

Cancer Mortality in Chinese Chrysotile Asbestos Miners: Exposure-Response Relationships

ObjectiveThis study was conducted to assess the relationship of mortality from lung cancer and other selected causes to asbestos exposure levels.MethodsA cohort of 1539 male workers from a chrysotile mine in China was followed for 26 years. Data on vital status, occupation and smoking were collected from the mine records and individual contacts. Causes and dates of death were further verified from the local death registry. Individual cumulative fibre exposures (f-yr/ml) were estimated based on converted dust measurements and working years at specific workshops. Standardized mortality ratios (SMRs) for lung cancer, gastrointestinal (GI) cancer, all cancers and nonmalignant respiratory diseases (NMRD) stratified by employment years, estimated cumulative fibre exposures, and smoking, were calculated. Poisson models were fitted to determine exposure-response relationships between estimated fibre exposures and cause-specific mortality, adjusting for age and smoking.ResultsSMRs for lung cancer increased with employment years at entry to the study, by 3.5-fold in ≥10 years and 5.3-fold in ≥20 years compared with <10 years. A similar trend was seen for NMRD. Smokers had greater mortality from all causes than nonsmokers, but the latter also had slightly increased SMR for lung cancer. No excess lung cancer mortality was observed in cumulative exposures of <20 f-yrs/ml. However, significantly increased mortality was observed in smokers at the levels of ≥20 f-yrs/ml and above, and in nonsmokers at ≥100 f-yrs/ml and above. A similarly clear gradient was also displayed for NMRD. The exposure-response relationships with lung cancer and NMRD persisted in multivariate analysis. Moreover, a clear gradient was shown in GI cancer mortality when age and smoking were adjusted for.ConclusionThere were clear exposure-response relationships in this cohort, which imply a causal link between chrysotile asbestos exposure and lung cancer and nonmalignant respiratory diseases, and possibly to gastrointestinal cancer, at least for smokers.

Pulmonary tuberculosis and lung cancer mortality in a historical cohort of workers with asbestosis

To examine pulmonary tuberculosis (PTB) infection and lung cancer mortality among workers with asbestosis in Hong Kong. Historical cohort study. All 124 male incident cases of asbestosis registered at the Pneumoconiosis Clinic of the Tuberculosis and Chest Service of the Department of Health between 1981 and 2008 were recruited and followed-up until 2008 to ascertain vital status and underlying causes of death. Standardized mortality ratios (SMRs) were calculated using the person-year method. Axelson's indirect method was used to adjust for the potential confounding effect of cigarette smoking. Forty-five patients (36.29%) had a history of PTB at the time of asbestosis diagnosis. The SMR of lung cancer was 5.22 [95% confidence interval (CI) 1.08-15.25] for subjects with a history of PTB, and this was reduced to 2.35 (95% CI 0.49-6.85) after indirect adjustment for smoking. Among asbestosis workers without a history of PTB, the SMR after indirect adjustment for smoking was 4.25 (95% CI 1.55-9.25) and 5.92 (95% CI 1.92-13.79) for those with comorbidities and those without comorbidities, respectively. Compared with other workers, those with a history of PTB had the highest all-cause SMR (6.73, 95% CI 4.55-9.63) and very high mortality due to heart diseases. This historical cohort study revealed that the prevalence of PTB infection was high among workers with asbestosis in Hong Kong. An excess risk of lung cancer mortality was observed among workers with a history of PTB, but the risk was lower than that seen among workers without a history of PTB. These interesting findings need to be confirmed by future studies.