Morbidity and mortality in relation to smoking among women and men of Chinese ethnicity: the Singapore Chinese Health Study

Longitudinal Changes in Smoking Habits in Women and Subsequent Risk of Cancer

INTRODUCTION

This study investigated the association between longitudinal smoking habit changes and cancer risk in a cohort of Korean women.

METHODS

Study population included women aged ≥40 years who underwent 2 biennial cancer screenings (2009-2010 and 2011-2012) and were followed up until 2020. This analysis was conducted in 2021. On the basis of changes in smoking habits, participants were grouped into sustained nonsmokers, sustained quitters, new quitters, relapsers, smoking initiators, and sustained smokers. Outcomes included incident cancer cases, smoking-related cancers, and specific cancer sites.

RESULTS

Of 3,051,946 women, the mean age was 54.8 years, and the median follow-up was 8.9 years. Compared with sustained nonsmokers, other groups had a significantly increased risk of cancer and smoking-related cancers: sustained quitters (adjusted hazard ratio=1.05; 95% CI=1.01, 1.09), new quitters (adjusted hazard ratio=1.12; 95% CI=1.07, 1.17), and sustained smokers (adjusted hazard ratio=1.14; 95% CI=1.09, 1.19). A significantly increased risk of lung, stomach, liver, and pancreas cancers was found in sustained smokers and new quitters. Relapsers/smoking initiators showed a higher risk of liver, lung, and breast cancer than sustained nonsmokers, but the strength of their corresponding adjusted hazard ratio was generally lower than that of sustained smokers. The hazard ratio of cancer risk was 0.92 (95% CI=0.87, 0.97) among sustained quitters and 0.97 (95% CI=0.91, 1.03) among new quitters relative to that among sustained smokers.

CONCLUSIONS

This study found a significant association between changes in smoking behavior and cancer risk. These findings suggest that smoking cessation is critical for cancer prevention in women.

Sex Difference and Smoking Effect of Lung Cancer Incidence in Asian Population

Simple Summary

This study analyzed the sex difference in the effect of smoking exposure on lung cancer in terms of absolute and relative risks despite the increasing lung cancer incidence in Asian female never smokers. Lung cancer risk is positively associated with the duration of smoking, quantity of smoking, and pack-years of smoking, and negatively associated with the number of years since smoking cessation for both sexes. However, higher lung cancer incidence in men than in women with the same level of smoking exposure was observed, suggesting a higher susceptibility for lung cancer in men. Sex should be considered in combination with smoking history in the selection of a lung cancer screening target population.

Abstract

This study analyzed the sex difference in the effect of smoking exposure on lung cancer in terms of absolute and relative risks despite the increasing lung cancer incidence in Asian female never smokers. A retrospective cohort study was conducted on individuals aged 40–79 years who participated in the national health screening program in 2007 and 2008 with linkage to the Korea Central Cancer Registry records. We evaluated sex differences in the age-standardized incidence rate (ASR) of lung cancer by smoking history and the hazard ratio (HR) after adjusting for potential confounders. ASRs for male and female never smokers were 92.5 and 38.3 per 100,000 person-years, respectively (rate ratio (RR) = 2.4; 95% confidence interval (CI) = 2.3–2.5). ASRs for male and female current smokers with a 30 pack-year smoking history were 305.3 and 188.4 per 100,000 person-years, respectively (RR = 1.6; 95% CI = 1.3–2.0). Smoking was significantly associated with lung cancer risk for both sexes. HRs for former smokers versus never smokers were 1.27 (95% CI = 1.23–1.33) for men and 1.43 (95% CI = 1.16–1.81) for women. HRs for current smokers versus never smokers were 2.71 (95% CI = 2.63–2.79) for men and 2.70 (95% CI = 2.48–2.94) for women. HRs for lung cancer increased similarly in both men and women according to smoking status. However, among Korean individuals with comparable smoking statuses, lung cancer incidence is higher in men than in women. Sex should be considered in combination with smoking history in the selection of a lung cancer screening target population.

Impact of Combined Lifestyle Factors on All-Cause and Cause-Specific Mortality and Life Expectancy in Chinese: The Singapore Chinese Health Study

BACKGROUND

To examine the impact of combined lifestyle factors on premature mortality and life expectancy in Chinese adults.

METHODS

A total of 44,052 Chinese adults aged 45-74 years free of cardiovascular disease (CVD), cancer, and diabetes were followed from recruitment (1993-1998) to the end of 2016 in the Singapore Chinese Health Study. A composite score (0-5 scale) was calculated based on five baseline healthy lifestyle factors including healthy diet, nonsmoking status, light to moderate alcohol drinking, being physically active and optimal body mass index. Mortality cases were identified through linkage with the nationwide death registry.

RESULTS

Adopting five healthy versus none was associated with a lower risk of all-cause and cause-specific mortality, and the hazard ratio (95% confidence interval [CI]) was 0.38 (0.29, 0.51) for all-cause mortality, 0.26 (0.13, 0.52) for CVD mortality, and 0.59 (0.37, 0.92) for cancer mortality. Nonadherence to 4-5 healthy lifestyle factors accounted for 34.9% (95% CI = 29.2, 40.2) in population attributable fraction for all-cause mortality, 35.1% (23.7, 44.9) for CVD mortality, and 18.0% (6.5, 28.0) for cancer mortality. Conversely, adherence to 4-5 healthy lifestyle factors versus none could achieve a gain of 8.1 years in women and 6.6 years in men for the life expectancy at 50 years.

CONCLUSIONS

A healthier lifestyle is associated with a substantially reduced risk of mortality and a longer life expectancy in the Chinese population. Our findings highlight the necessity of coordinated actions targeting combined lifestyle factors in reducing the overall burden of diseases and premature deaths.

The future burden of kidney and bladder cancers preventable by behavior modification in Australia: A pooled cohort study

Substantial changes in the prevalence of the principal kidney and bladder cancer risk factors, smoking (both cancers) and body fatness (kidney cancer), have occurred but the contemporary cancer burden attributable to these factors has not been evaluated. We quantified the kidney and bladder cancer burden attributable to individual and joint exposures and assessed whether these burdens differ between population subgroups. We linked pooled data from seven Australian cohorts (N = 367,058) to national cancer and death registries and estimated the strength of the associations between exposures and cancer using adjusted proportional hazards models. We estimated exposure prevalence from representative contemporaneous health surveys. We combined these estimates to calculate population attributable fractions (PAFs) with 95% confidence intervals (CIs), accounting for competing risk of death, and compared PAFs for population subgroups. During the first 10-year follow-up, 550 kidney and 530 bladder cancers were diagnosed and over 21,000 people died from any cause. Current levels of overweight and obesity explain 28.8% (CI = 17.3-38.7%), current or past smoking 15.5% (CI = 6.0-24.1%) and these exposures jointly 39.6% (CI = 27.5-49.7%) of the kidney cancer burden. Current or past smoking explains 44.4% (CI = 35.4-52.1%) of the bladder cancer burden, with 24.4% attributable to current smoking. Ever smoking explains more than half (53.4%) of the bladder cancer burden in men, and the burden potentially preventable by quitting smoking is highest in men (30.4%), those aged <65 years (28.0%) and those consuming >2 standard alcoholic drinks/day (41.2%). In conclusion, large fractions of kidney and bladder cancers in Australia are preventable by behavior change.

A nomogram to predict prognosis in patients undergoing sublobar resection for stage IA non-small-cell lung cancer

Introduction

This study aimed to develop a practical nomogram to predict prognosis in patients who are undergoing sublobar resection for stage IA non-small-cell lung cancer (NSCLC). Data from Surveillance, Epidemiology, and End Results (SEER) databases were used to construct the nomogram.

Methods

Data from patients undergoing sublobar resection for stage IA NSCLC diagnosed between 2004 and 2014 were extracted from the SEER database. Factors that may predict the outcome were identified using the Kaplan–Meier method and the Cox proportional-hazards model. A nomogram was constructed to predict the 3- and 5-year overall survival (OS) and lung cancer-specific survival (LCSS) rates of these patients. The predictive accuracy of the nomogram was measured using the concordance index (C-index) and calibration curve.

Results

A total of 4,866 patients were selected for this study. Using univariate and multivariate analyses, eight independent prognostic factors associated with OS were identified, including sex (P<0.001), age (P<0.001), race (P=0.043), marital status (P=0.009), pathology (P=0.004), differentiation (P<0.001), tumor size (P<0.001), and surgery (P=0.001), and five independent prognostic factors associated with LCSS were also identified, including sex (P<0.001), age (P<0.001), differentiation (P<0.001), tumor size (P<0.001), and surgery (P=0.011). A nomogram was established based on these results and validated using the internal bootstrap resampling method. The C-index of the established nomogram for OS and LCSS was 0.649 (95% CI: 0.635–0.663) and 0.640 (95% CI: 0.622–0.658), respectively. The calibration curves for probability of 3-, and 5-year OS and LCSS rates demonstrated good agreement between the nomogram prediction and actual observation.

Conclusion

This innovative nomogram delivered a relatively accurate individual prognostic prediction for patients undergoing sublobar resection for stage IA NSCLC.

The future burden of lung cancer attributable to current modifiable behaviours: a pooled study of seven Australian cohorts

Background

Knowledge of preventable disease and differences in disease burden can inform public health action to improve health and health equity. We quantified the future lung cancer burden preventable by behavioural modifications across Australia.

Methods

We pooled seven Australian cohort studies (n = 367 058) and linked them to national registries to identify lung cancers and deaths. We estimated population attributable fractions and their 95% confidence intervals (CIs) for modifiable risk factors, using risk estimates from the cohort data and risk factor exposure distribution from contemporary national health surveys.

Results

During the first 10-year follow-up, there were 2025 incident lung cancers and 20 349 deaths. Stopping current smoking could prevent 53.7% (95% CI, 50.0-57.2%) of lung cancers over 40 years and 18.3% (11.0-25.1%) in 10 years. The smoking-attributable burden is highest in males, those who smoke <20 cigarettes per day, are <75 years of age, unmarried, of lower educational attainment, live in remote areas or are healthy weight. Increasing physical activity and fruit consumption, if causal, could prevent 15.6% (6.9-23.4%) and 7.5% (1.3-13.3%) of the lung cancer burden, respectively. Jointly, the three behaviour modifications could prevent up to 63.0% (58.0-67.5%) of lung cancers in 40 years, and 31.2% (20.9-40.1%) or 43 300 cancers in 10 years. The preventable burden is highest among those with multiple risk factors.

Conclusions

Smoking remains responsible for the highest burden of lung cancer in Australia. The uneven burden distribution distinguishes subgroups that could benefit the most from activities to control the world's deadliest cancer.

Smoking as a risk factor for lung cancer in women and men: a systematic review and meta-analysis

OBJECTIVES

To investigate the sex-specific association between smoking and lung cancer.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

We searched PubMed and EMBASE from 1 January 1999 to 15 April 2016 for cohort studies. Cohort studies before 1 January 1999 were retrieved from a previous meta-analysis. Individual participant data from three sources were also available to supplement analyses of published literature.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Cohort studies reporting the sex-specific relative risk (RR) of lung cancer associated with smoking.

RESULTS

Data from 29 studies representing 99 cohort studies, 7 million individuals and >50 000 incident lung cancer cases were included. The sex-specific RRs and their ratio comparing women with men were pooled using random-effects meta-analysis with inverse-variance weighting. The pooled multiple-adjusted lung cancer RR was 6.99 (95% Confidence Interval (CI) 5.09 to 9.59) in women and 7.33 (95% CI 4.90 to 10.96) in men. The pooled ratio of the RRs was 0.92 (95% CI 0.72 to 1.16; I2=89%; p<0.001), with no evidence of publication bias or differences across major pre-defined participant and study subtypes. The women-to-men ratio of RRs was 0.99 (95% CI 0.65 to 1.52), 1.11 (95% CI 0.75 to 1.64) and 0.94 (95% CI 0.69 to 1.30), for light, moderate and heavy smoking, respectively.

CONCLUSIONS

Smoking yields similar risks of lung cancer in women compared with men. However, these data may underestimate the true risks of lung cancer among women, as the smoking epidemic has not yet reached full maturity in women. Continued efforts to measure the sex-specific association of smoking and lung cancer are required.

Gender differences in the correlation between prognosis and postoperative weight loss in patients with non-small cell lung cancer

OBJECTIVES

The aim of this study was to investigate gender differences in the relationship between preoperative body mass index (BMI), postoperative body weight change and prognosis in patients with non-small cell lung cancer (NSCLC).

METHODS

Two hundred and sixty-three patients with NSCLC were enrolled in this study. Preoperative BMI was categorized based on WHO definition as follows: underweight (BMI <18.5): 21 patients (8.0%), normal (18.5 ≦ BMI <25): 179 patients (68%), overweight and obese (BMI ≧25): 63 patients (24%). Several factors such as age, sex, cancer stage, body weight change and BMI were recorded and correlated to the postoperative overall survival (OS).

RESULTS

For male patients, those in the low-BMI group had the worst prognosis (P < 0.05) whereas female patients with low BMI did not. Male patients with low BMI had statistically significant poorer prognosis compared to corresponding female patients (P < 0.05). Male patients with more than 5% body weight loss within 1 year after operation when compared to preoperative body weight had poorer prognosis than those with less than 5% body weight loss (P < 0.001). Furthermore, these male patients had statistically significant worse prognosis than the corresponding female patients (P < 0.05). In multivariable analysis, gender, more than 5% of body weight loss compared to preoperative body weight, and pathological stage were independent prognostic factors in NSCLC.

CONCLUSIONS

This study illustrates significant gender differences in the relationship between prognosis and BMI or body weight change in patients with postoperative NSCLC.

Assessing Health Impacts of Pictorial Health Warning Labels on Cigarette Packs in Korea Using DYNAMO-HIA

OBJECTIVES

This study aimed to predict the 10-year impacts of the introduction of pictorial warning labels (PWLs) on cigarette packaging in 2016 in Korea for adults using DYNAMO-HIA.

METHODS

In total, four scenarios were constructed to better understand the potential health impacts of PWLs: two for PWLs and the other two for a hypothetical cigarette tax increase. In both policies, an optimistic and a conservative scenario were constructed. The reference scenario assumed the 2015 smoking rate would remain the same. Demographic data and epidemiological data were obtained from various sources. Differences in the predicted smoking prevalence and prevalence, incidence, and mortality from diseases were compared between the reference scenario and the four policy scenarios.

RESULTS

It was predicted that the optimistic PWLs scenario (PWO) would lower the smoking rate by 4.79% in males and 0.66% in females compared to the reference scenario in 2017. However, the impact on the reduction of the smoking rate was expected to diminish over time. PWO will prevent 85 238 cases of diabetes, 67 948 of chronic obstructive pulmonary disease, 31 526 of ischemic heart disease, 21 036 of lung cancer, and 3972 prevalent cases of oral cancer in total over the 10-year span due to the reductions in smoking prevalence. The impacts of PWO are expected to be between the impact of the optimistic and the conservative cigarette tax increase scenarios. The results were sensitive to the transition probability of smoking status.

CONCLUSIONS

The introduction of PWLs in 2016 in Korea is expected reduce smoking prevalence and disease cases for the next 10 years, but regular replacements of PWLs are needed for persistent impacts.

The fractions of cancer attributable to modifiable factors: A global review

Worldwide, the burden of cancer is rising, stimulating efforts to develop strategies to control these diseases. Primary prevention, a key control strategy, aims to reduce cancer incidence through programs directed towards reducing population exposure to known causal factors. Before enacting such strategies, it is necessary to estimate the likely effect on cancer incidence if exposures to known causal factors were reduced or eliminated. The population attributable fraction (PAF) is the epidemiological measure which quantifies this potential reduction in incidence. We surveyed the literature to document and summarise the proportions of cancers across the globe attributable to modifiable causes, specifically tobacco smoke, alcohol, overweight/obesity, insufficient physical activity, solar ultraviolet (UV) radiation and dietary factors (insufficient fruit, non-starchy vegetables and fibre; red/processed meat; salt). In total, we identified 55 articles that presented PAF estimates for one or more causes. Information coverage was not uniform, with many articles reporting cancer PAFs due to overweight/obesity, alcohol and tobacco, but fewer reporting PAFs for dietary factors or solar UV radiation. At all cancer sites attributable to tobacco and alcohol, median PAFs were markedly lower for women than men. Smoking contributed to very high median PAFs (>50%) for cancers of the lung and larynx. Median PAFs for men, attributable to alcohol, were high (25-50%) for cancers of the oesophagus, oral cavity/pharynx, larynx and liver. For cancers causally associated with overweight/obesity, high median PAFs were reported for oesophageal adenocarcinoma (men 29%, women 37%), gallbladder (men 11%, women 42%) and endometrium (36%). The cancer PAF literature is growing rapidly. Repeating this survey in the future should lead to more precise estimates of the potentially preventable fractions of cancer.

Using the Negative Exponential Model to Describe Changes in Risk of Smoking-Related Diseases following Changes in Exposure to Tobacco

Recently published analyses for four smoking-related diseases show that the declining excess relative risk by time quit is well fitted by the negative exponential model. These analyses estimated the half-life of this excess, that is, the time after quitting when the excess relative risk reaches half that for continuing smokers. We describe extensions of the simple model. One quantifies the decline following an exposure reduction. We show that this extension satisfactorily predicts results from studies investigating the effect of reducing cigarette consumption. It may also be relevant to exposure reductions following product-switching. Another extension predicts changes in excess relative risk occurring following multiple exposure changes over time. Suitable published epidemiological data are unavailable to test this, and we recommend its validity to be investigated using large studies with data recorded on smoking habits at multiple time points in life. The basic formulae described assume that the excess relative risk for a continuing smoker is linearly related to exposure and that the half-life is invariant of age. We describe model adaptations to allow for nonlinear dose-response and for age-dependence of the half-life. The negative exponential model, though relatively simple, appears to have many potential uses in epidemiological research for summarizing variations in risk with exposure changes.

A retrospective analysis of the association between tobacco smoking and deaths from respiratory and cardiovascular diseases in the Kassena-Nankana districts of Northern Ghana

BACKGROUND

Tobacco use is a public health problem, responsible for approximately six million deaths annually worldwide. It is a risk factor for many diseases including cancers, respiratory and cardiovascular diseases. In low-and middle-income countries, respiratory and cardiovascular diseases are important causes of death. Tobacco use is prevalent in Ghana, but no study had examined the relationship between tobacco use and deaths from respiratory and cardiovascular diseases in the Upper East Region of Northern Ghana. Hence the paper assessed the association between tobacco use and deaths from respiratory and cardiovascular diseases in that region.

METHODS

The study used verbal autopsy data collected from the Kassena-Nankana East and West districts of the Upper East Region of Northern Ghana. Data from deceased individuals aged 15 to 59 years whose deaths occurred between January 1, 2004 and December 31, 2011 and with a known cause as well as smoking status were analyzed. Two binary outcome variables were generated from the cause of death data; whether an individual died from respiratory diseases or not, and from cardiovascular diseases or not. Multiple logistic regression models were used to assess the relationship between tobacco use and deaths from respiratory and cardiovascular diseases.

RESULTS

Out of 3,492 deaths with a known cause of death and smoking status, a third of them smoked. About 16.6% of smokers and 8.1% of non-smokers died from respiratory diseases. Approximately, 10.7% of smokers died from cardiovascular diseases compared to 10.6% of non-smokers. In multivariate analyses, individuals with a history of smoking had two-fold increased odds [OR=2.18, 95% CI (1.6-2.9)] of dying from respiratory diseases. Besides, the number of years of smoking as well as the frequency of smoking is significantly associated with deaths from respiratory diseases. No association existed between tobacco use and deaths from cardiovascular diseases.

CONCLUSIONS

Within our study we identified a strong relationship between tobacco use and deaths from respiratory diseases, but not an association with deaths from cardiovascular diseases. Our findings highlight the need to make appropriate health interventions to control tobacco use and thus help reduce premature deaths from respiratory and other tobacco linked diseases.

Association between COX-2 polymorphisms and non-small cell lung cancer susceptibility

AIM

To explore the association between COX-2 polymorphisms and non-small cell lung cancer (NSCLC) susceptibility.

METHODS

We collected fasting peripheral venous blood from 60 cases with NSCLC and 62 healthy controls through physical examinations, and applied PCR-RFLP to analyze COX-2 polymorphisms of two groups.

RESULTS

With respect to detecting COX-2 rs689466 and rs5275 polymorphisms, the distribution frequency of mutant genotype AA of COX-2 rs689466 in case group was higher than that in control group, which possessed significant difference between two groups (P<0.05). Carriers with AA genotype were 4.05 times at risk of NSCLC than those with GG genotype (P = 0.04, OR=4.05, 95% CI=1.14-14.43). The distribution of mutant genotype CC of COX-2 rs5275 was different between two groups, and carriers with genotype CC were at 5.70 times higher risk of NSCLC than those with genotype TT. After corrected by sex, gender, smoking and drinking factors, AA genotype of COX-2 rs689466 and CC genotype of COX-2 rs5275 still contributed to increased risk of NSCLC (OR=4.22, 95% CI=1.10-16.17, OR=6.95, 95% CI=1.27-38.11). After analyzed of linkage disequilibrium (LD) and haplotypes of alleles in two SNPs, the distribution frequency of A-C haplotype in case group was higher than that in control group, with significant difference between two groups (P<0.05). After corrected by sex, gender, smoking and drinking factors, statistical difference was still found in the total distribution of A-C haplotype between two groups (P=0.03, OR=6.11, 95% CI=1.16-32.2).

CONCLUSIONS

COX-2 rs689466 and rs5275 polymorphisms may be related to NSCLC susceptibility. And A-C haplotype might be a susceptibility haplotype for NSCLC.

Metabolites of tobacco smoking and colorectal cancer risk

Colorectal cancer is not strictly considered a tobacco-related malignancy, but modest associations have emerged from large meta-analyses. Most studies, however, use self-reported data, which are subject to misclassification. Biomarkers of tobacco exposure may reduce misclassification and provide insight into metabolic variability that potentially influences carcinogenesis. Our aim was to identify metabolites that represent smoking habits and individual variation in tobacco metabolism, and investigate their association with colorectal cancer. In a nested case-control study of 255 colorectal cancers and 254 matched controls identified in the Prostate, Lung, Colorectal and Ovarian cancer screening trial, baseline serum was used to identify metabolites by ultra-high-performance liquid-phase chromatography and mass spectrometry, as well as gas chromatography with tandem mass spectrometry. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by logistic regression. Self-reported current smoking was associated with serum cotinine, O-cresol sulfate and hydroxycotinine. Self-reported current smoking of any tobacco (OR = 1.90, 95% CI: 1.02-3.54) and current cigarette smoking (OR = 1.51, 95% CI: 0.75-3.04) were associated with elevated colorectal cancer risks, although the latter was not statistically significant. Individuals with detectable levels of hydroxycotinine had an increased colorectal cancer risk compared with those with undetectable levels (OR = 2.68, 95% CI: 1.33-5.40). Although those with detectable levels of cotinine had a suggestive elevated risk of this malignancy (OR = 1.81, 95% CI: 0.98-3.33), those with detectable levels of O-cresol sulfate did not (OR = 1.16, 95% CI: 0.57-2.37). Biomarkers capturing smoking behavior and metabolic variation exhibit stronger associations with colorectal cancer than self-report, providing additional evidence for a role for tobacco in this malignancy.

Changes in smoking behavior and subsequent mortality risk during a 35-year follow-up of a cohort in Xi'an, China

Prospective evidence of the associations of smoking cessation with chronic obstructive pulmonary disease (COPD) and other causes of death in Asia is scarce. Previous studies, which were mostly based on baseline smoking behavior only, were subject to sick-quitter bias and misclassification resulting from changes in smoking behavior during follow-up. We followed up a cohort for 18 years (1976-1994) to assess changes in smoking behavior and then for an additional 17 years (1994-2011) to examine the relationships of continuing to smoke and new quitting with mortality risk in 1,494 Chinese people (961 men, 533 women). Of the baseline current smokers, 38.7% quit between 1976 and 1994. From 1994 to 2011, a total of 488 persons (359 men, 129 women) died. Ever smokers had increased risks of lung cancer, coronary heart disease, thrombotic stroke, and COPD, with dose-response relationships. For all tobacco-related mortality, the relative risk for new quitters compared with continuing smokers was 0.68 (95% confidence interval: 0.46, 0.99) for those who had quit 2-7 years previously and 0.56 (95% confidence interval: 0.37, 0.85) for those who had quit 8 years or more previously. The corresponding relative risks were 0.69 and 0.45 for lung cancer, 0.78 and 0.51 for coronary heart disease, 0.76 and 0.84 for thrombotic stroke, and 0.89 and 0.61 for COPD, respectively. Smoking increased tobacco-related deaths, and particularly deaths from COPD, in China, whereas quitting at middle age (at approximately 50 years of age) substantially reduced the risks of death from these causes. The benefits of smoking cessation were underestimated in previous studies that did not use repeated measures.

Estimating the decline in excess risk of chronic obstructive pulmonary disease following quitting smoking - a systematic review based on the negative exponential model

We quantified the decline in COPD risk following quitting using the negative exponential model, as previously carried out for other smoking-related diseases. We identified 14 blocks of RRs (from 11 studies) comparing current smokers, former smokers (by time quit) and never smokers, some studies providing sex-specific blocks. Corresponding pseudo-numbers of cases and controls/at risk formed the data for model-fitting. We estimated the half-life (H, time since quit when the excess risk becomes half that for a continuing smoker) for each block, except for one where no decline with quitting was evident, and H was not estimable. For the remaining 13 blocks, goodness-of-fit to the model was generally adequate, the combined estimate of H being 13.32 (95% CI 11.86-14.96) years. There was no heterogeneity in H, overall or by various studied sources. Sensitivity analyses allowing for reverse causation or different assumed times for the final quitting period little affected the results. The model summarizes quitting data well. The estimate of 13.32years is substantially larger than recent estimates of 4.40years for ischaemic heart disease and 4.78years for stroke, and also larger than the 9.93years for lung cancer. Heterogeneity was unimportant for COPD, unlike for the other three diseases.

Smoking as a risk factor for stroke in women compared with men: a systematic review and meta-analysis of 81 cohorts, including 3,980,359 individuals and 42,401 strokes

BACKGROUND AND PURPOSE

It is currently unknown whether the excess risk of stroke by smoking is the same for women and men. We performed a systematic review and meta-analysis to estimate the effect of smoking on stroke in women compared with men.

METHODS

PubMed MEDLINE was systematically searched for prospective population-based cohort studies published between January 1, 1966, and January 26, 2013. Studies that presented sex-specific estimates of the relative risk of stroke comparing current smoking with nonsmoking and its associated variability were selected. The sex-specific relative risks and their ratio (RRR), comparing women with men, were pooled using random-effects meta-analysis with inverse variance weighting. Similarly, the RRR for former versus never smoking was pooled.

RESULTS

Data from 81 prospective cohort studies that included 3,980,359 individuals and 42,401 strokes were available. Smoking was an independent risk factor for stroke in both sexes. Overall, the pooled multiple-adjusted RRR indicated a similar risk of stroke associated with smoking in women compared with men (RRR, 1.06 [95% confidence interval, 0.99-1.13]). In a regional analysis, there was evidence of a more harmful effect of smoking in women than in men in Western (RRR, 1.10 [1.02-1.18)] but not in Asian (RRR, 0.97 [0.87-1.09]) populations. Compared with never-smokers, the beneficial effects of quitting smoking among former smokers on stroke risk were similar between the sexes (RRR, 1.10 [0.99-1.22]).

CONCLUSIONS

Compared with nonsmokers, the excess risk of stroke is at least as great among women who smoke compared with men who smoke.

A prospective study of tobacco smoking and mortality in Bangladesh

Background

Limited data are available on smoking-related mortality in low-income countries, where both chronic disease burden and prevalence of smoking are increasing.

Methods

Using data on 20, 033 individuals in the Health Effects of Arsenic Longitudinal Study (HEALS) in Bangladesh, we prospectively evaluated the association between tobacco smoking and all-cause, cancer, and cardiovascular disease mortality during ∼7.6 years of follow-up.

Cox proportional hazards models were used to estimate hazard ratios (HRs) and their 95% confidence intervals (CIs) for deaths from all-cause, cancer, CVD, ischemic heart disease (IHD), and stroke, in relation to status, duration, and intensity of cigarette/bidi and hookah smoking.

Results

Among men, cigarette/bidi smoking was positively associated with all-cause (HR 1.40, 95% CI 1.06 1.86) and cancer mortality (HR 2.91, 1.24 6.80), and there was a dose-response relationship between increasing intensity of cigarette/bidi consumption and increasing mortality. An elevated risk of death from ischemic heart disease (HR 1.87, 1.08 3.24) was associated with current cigarette/bidi smoking. Among women, the corresponding HRs were 1.65 (95% CI 1.16 2.36) for all-cause mortality and 2.69 (95% CI 1.20 6.01) for ischemic heart disease mortality. Similar associations were observed for hookah smoking. There was a trend towards reduced risk for the mortality outcomes with older age at onset of cigarette/bidi smoking and increasing years since quitting cigarette/bibi smoking among men. We estimated that cigarette/bidi smoking accounted for about 25.0% of deaths in men and 7.6% in women.

Conclusions

Tobacco smoking was responsible for substantial proportion of premature deaths in the Bangladeshi population, especially among men. Stringent measures of tobacco control and cessation are needed to reduce tobacco-related deaths in Bangladesh.

Cigarette smoking as a risk factor for coronary heart disease in women compared with men: a systematic review and meta-analysis of prospective cohort studies

BACKGROUND

Prevalence of smoking is increasing in women in some populations and is a risk factor for coronary heart disease. Whether smoking confers the same excess risk of coronary heart disease for women as it does for men is unknown. Therefore, we aimed to estimate the effect of smoking on coronary heart disease in women compared with men after accounting for sex differences in other major risk factors.

METHODS

We undertook a systematic review and meta-analysis of prospective cohort studies published between Jan 1, 1966, and Dec 31, 2010, from four online databases. We selected cohort studies that were stratified by sex with measures of relative risk (RR), and associated variability, for coronary heart disease and current smoking compared with not smoking. We pooled data with a random effects model with inverse variance weighting, and estimated RR ratios (RRRs) between men and women.

FINDINGS

We reviewed 8005 abstracts and included 26 articles with data for 3,912,809 individuals and 67,075 coronary heart disease events from 86 prospective trials. In 75 cohorts (2·4 million participants) that adjusted for cardiovascular risk factors other than coronary heart disease, the pooled adjusted female-to-male RRR of smoking compared with not smoking for coronary heart disease was 1·25 (95% CI 1·12-1·39, p<0·0001). This outcome was unchanged after adjustment for potential publication bias and there was no evidence of important between-study heterogeneity (p=0·21). The RRR increased by 2% for every additional year of study follow-up (p=0·03). In pooled data from 53 studies, there was no evidence of a sex difference in the RR between participants who had previously smoked compared with those who never had (RRR 0·96, 95% CI 0·86-1·08, p=0·53).

INTERPRETATION

Whether mechanisms underlying the sex difference in risk of coronary heart disease are biological or related to differences in smoking behaviour between men and women is unclear. Tobacco-control programmes should consider women, particularly in those countries where smoking among young women is increasing in prevalence.

FUNDING

None.

Cigarette smoking and risk of prostate cancer among Singapore Chinese

Prospective epidemiologic studies conducted in Western populations support an association between current smoking and aggressive subtypes of prostate cancer. In Singapore, where prostate-specific antigen is not used for population-wide screening, prostate cancer incidence has tripled within the past two decades. Using Cox regression methods, we examined the relationship between smoking and prostate cancer established between 1993 and 1998 in a cohort of 27,293 Singapore Chinese men. As of December 2006, 250 incident prostate cancer cases were diagnosed. In our cohort, 42.2% reported never smoking cigarettes, 15.7% quit over 5 years ago (long-term former), 5.7% quit within the past 5 years (recent former), and 36.4% were current smokers. From multivariable models, we observed no association with smoking status, age at starting to smoke, years smoked, or number of cigarettes per day. Among recent former and current smokers combined, we observed a small positive association for earlier age at starting to smoke that was somewhat stronger for nonadvanced disease (hazard ratio = 1.63, 95% confidence interval: 0.85, 3.12, for <15 years versus nonsmokers). Smoking was not a major risk factor for prostate cancer in our Singapore Chinese cohort, a traditionally low risk population with parallel increases in incidence and mortality.

Consequences of smoking during pregnancy on maternal health

OBJECTIVE

To estimate the incidence of maternal cardiovascular and pulmonary events and the prevalence of other comorbid conditions among pregnant smokers.

METHODS

We queried the Nationwide Inpatient Sample (NIS) from the Healthcare Cost and Utilization Project (HCUP) of the Agency for Healthcare Research and Quality (AHRQ) for pregnancy-related discharge codes for the years 2000-2004. The prevalence of various conditions and the incidence of various complications were compared between smokers and nonsmokers.

RESULTS

The majority of smokers were young and white and had public insurance. Smokers were more likely to have experienced deep vein thrombosis (odds ratio [OR] 1.3, 95% confidence interval [CI] 1.1, 1.6), stroke (OR 1.7, 95% CI 1.2, 2.5), pulmonary embolus (OR 2.5, 95% CI 2.1, 3.0), and myocardial infarction (OR 4.6, 95% CI 3.3, 6.4). They were 3 times more likely to have experienced influenza or pneumonia (OR 2.9, 95% CI 2.7, 3.2) and 15 times more likely to have bronchitis (OR 15.2, 95% CI 12.8, 18.2). They were more likely to suffer from a number of comorbidities, including asthma (OR 4.0, 95% CI 3.7, 4.2) and gastrointestinal ulcers (OR 3.7, 95% CI 2.6, 5.5). Although they were less likely to have experienced gestational diabetes (OR 0.9, 95% CI 0.9, 1.0), preeclampsia (OR 0.8, 95% CI 0.8, 0.9), or eclampsia (OR 0.7, 95% CI 0.6, 0.9), they were more than 5 times as likely to have experienced an ectopic pregnancy (OR 5.4, 95% CI 4.6, 6.3).

CONCLUSIONS

Smoking has a negative impact on maternal health. Counseling about the risks of smoking in pregnancy should include not only fetal risks but maternal risks as well.

Meta- and pooled analysis of GSTP1 polymorphism and lung cancer: a HuGE-GSEC review

Lung cancer is the most common cancer worldwide. Polymorphisms in genes associated with carcinogen metabolism may modulate risk of disease. Glutathione S-transferase pi (GSTP1) detoxifies polycyclic aromatic hydrocarbons found in cigarette smoke and is the most highly expressed glutathione S-transferase in lung tissue. A polymorphism in the GSTP1 gene, an A-to-G transition in exon 5 (Ile105Val, 313A --> 313G), results in lower activity among individuals who carry the valine allele. The authors present a meta- and a pooled analysis of case-control studies that examined the association between this polymorphism in GSTP1 and lung cancer risk (27 studies, 8,322 cases and 8,844 controls and 15 studies, 4,282 cases and 5,032 controls, respectively). Overall, the meta-analysis found no significant association between lung cancer risk and the GSTP1 exon 5 polymorphism. In the pooled analysis, there was an overall association (odds ratio = 1.11, 95% confidence interval: 1.03, 1.21) between lung cancer and carriage of the GSTP1 Val/Val or Ile/Val genotype compared with those carrying the Ile/Ile genotype. Increased risk varied by histologic type in Asians. There appears to be evidence for interaction between amount of smoking, the GSTP1 exon 5 polymorphism, and risk of lung cancer in whites.