Modifying risk of developing lung cancer by changing habits of cigarette smoking

Absolute lung cancer risk increases among individuals with >15 quit-years: Analyses to inform the update of the American Cancer Society lung cancer screening guidelines

BACKGROUND

This report quantifies counteracting effects of quit-years and concomitant aging on lung cancer risk, especially on exceeding 15 quit-years, when the US Preventive Services Task Force (USPSTF) recommends curtailing lung-cancer screening.

METHODS

Cox models were fitted to estimate absolute lung cancer risk among Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (PLCO) and National Lung Screening Trial (NLST) participants who ever smoked. Absolute lung cancer risk and gainable years of life from screening for individuals aged 50 to 80 in the US-representative National Health Interview Survey (NHIS) 2015-2018 who ever smoked were projected. Relaxing USPSTF recommendations to 20/25/30 quit-years versus augmenting USPSTF criteria with individuals whose estimated gain in life expectancy from screening exceeded 16.2 days according to the Life Years From Screening-CT (LYFS-CT) prediction model was compared.

RESULTS

Absolute lung cancer risk increased by 8.7%/year (95% CI, 7.7%-9.7%; p < .001) as individuals aged beyond 15 quit-years in the PLCO, with similar results in NHIS and NLST. For example, mean 5-year lung cancer risk for those aged 65 years with 15 quit-years = 1.47% (95% CI, 1.35%-1.59%) versus 1.76% (95% CI, 1.62%-1.90%) for those aged 70 years with 20 quit-years in the PLCO. Removing the quit-year criterion would make 4.9 million more people eligible and increase the proportion of preventable lung cancer deaths prevented (sensitivity) from 63.7% to 74.2%. Alternatively, augmentation using LYFS-CT would make 1.7 million more people eligible while increasing the lung cancer death sensitivity to 74.0%.

CONCLUSIONS

Because of aging, absolute lung cancer risk increases beyond 15 quit-years, which does not support exemption from screening or curtailing screening once it has been initiated. Compared with relaxing the USPSTF quit-year criterion, augmentation using LYFS-CT could prevent most of the deaths at substantially superior efficiency, while also preventing deaths among individuals who currently smoke with low intensity or long duration.

Associations of Combustible Cigarette, Electronic Cigarette, and Dual Use With COVID Infection and Severity in the U.S.: A Cross-sectional Analysis of the 2021 National Health Information Survey

Given the potential respiratory health risks, the association of COVID infection and the use of combustible cigarettes, electronic nicotine delivery systems (ENDS), and concurrent dual use is a priority for public health. Many published reports have not accounted for known covarying factors. This study sought to calculate adjusted odds ratios for self-reported COVID infection and disease severity as a function of smoking and ENDS use, while accounting for factors known to influence COVID infection and disease severity (i.e., age, sex, race and ethnicity, socioeconomic status and educational attainment, rural or urban environment, self-reported diabetes, COPD, coronary heart disease, and obesity status). Data from the 2021 U.S. National Health Interview Survey, a cross-sectional questionnaire design, were used to calculate both unadjusted and adjusted odds ratios for self-reported COVID infection and severity of symptoms. Results indicate that combustible cigarette use is associated with a lower likelihood of self-reported COVID infection relative to non-use of tobacco products (AOR = .64; 95% CI [.55, .74]), whereas ENDS use is associated with a higher likelihood of self-reported COVID infection (AOR = 1.30; 95% CI [1.04, 1.63]). There was no significant difference in COVID infection among dual users (ENDS and combustible use) when compared with non-users. Adjusting for covarying factors did not substantially change the results. There were no significant differences in COVID disease severity between those of varying smoking status. Future research should examine the relationship between smoking status and COVID infection and disease severity utilizing longitudinal study designs and non-self-report measures of smoking status (e.g., the biomarker cotinine), COVID infection (e.g., positive tests), and disease severity (e.g., hospitalizations, ventilator assistance, mortality, and ongoing symptoms of long COVID).

Cigarette Smoking Reduction and Health Risks: A Systematic Review and Meta-analysis

Introduction

Studies have shown the health benefits of cigarette smoking cessation. However, the literature remains unclear about the relationship between smoking reduction and health risks. This comprehensive review and meta-analysis updates previous reviews with the newest estimates.

Aims and Methods

We conducted a systematic review and meta-analysis evaluating the association between smoking reduction and some health risks in observational studies. We defined the following smoking categories: heavy smokers smoked ≥15–20 cigarettes per day (CPD), moderate smokers smoked 10–19 CPD, and light smokers smoked &lt;10 CPD. The relative risks (RRs) and 95% confidence intervals (CIs) were estimated using random-effect models.

Results

We identified 19 studies including four case–control and 15 cohort studies. Compared with continuing heavy smokers, we found decreased lung cancer risk for those who reduced CPD by more than 50% (RR = 0.72, 95% CI: 0.52, 0.91), from heavy to moderate (RR = 0.66, 95% CI: 0.46, 0.85), and from heavy to light (RR = 0.60, 95% CI: 0.49, 0.72). We also found lower risk of cardiovascular disease (CVD) for those who reduced from heavy to light smoking (RR = 0.78, 95% CI: 0.67, 0.89) but not those who reduced by more than 50% and reduced smoking from heavy to moderate. We did not find any significant difference in all-cause mortality, all-cancer risks, and smoking-/tobacco-related cancer risk among those who reduced.

Conclusions

Substantial smoking reduction may decrease lung cancer risk but results on CVD (coronary heart disease and stroke combined) risk were mixed. The relationships between smoking reduction and other endpoints examined were not significant.

Implications

This meta-analysis helps clarify our understanding of various smoking reduction levels on some health risks. While smoking reduction may decrease risks of lung cancer, the relationships between smoking reduction and other endpoints, including all-cause mortality and cardiovascular disease, remain unclear. Although smoking reduction may decrease lung cancer risks, the magnitude of lung cancer risk remain high. Among smokers, complete cessation remains the most effective approach for cancer and CVD prevention.

Lifetime Smoking History and Risk of Lung Cancer: Results From the Framingham Heart Study

Background

The relative risk of lung cancer decreases with years since quitting (YSQ) smoking, but risk beyond 25 YSQ remains unclear. Current lung cancer screening guidelines, which exclude smokers with more than 15 YSQ, may not detect lung cancers in this population.

Methods

We analyzed data from Framingham Heart Study Original (n = 3905) and Offspring cohort (n = 5002) participants for lifetime smoking and lung cancer incidence from 1954 to 1958 (Exam 4) and 1971 to 1975 (Exam 1), respectively, through 2013. We used multivariable-adjusted Cox proportional hazards regression models to compare current, former, and never smokers and lung cancer risk. Smoking status and covariates were time-updated every two years (Original) or four years (Offspring). Primary analyses were restricted to heavy ever smokers with more than 21.3 pack-years; additional analyses included all ever smokers.

Results

On follow-up (median = 28.7 years), 284 lung cancers were detected: incidence rates/1000 person-years in current, former, and never smokers were 1.97 (95% confidence interval [CI] = 1.66 to 2.33), 1.61 (95% CI = 1.34 to 1.93), and 0.26 (95% CI = 0.17 to 0.39), respectively. Heavy former (vs never) smokers had elevated lung cancer risk at all YSQ (<5: hazard ratio [HR] = 12.12, 95% CI = 6.94 to 21.17; 5-9: HR = 11.77, 95% CI = 6.78 to 20.45; 10-14: HR = 7.81, 95% CI = 3.98 to 15.33; 15-24: HR = 5.88, 95% CI = 3.19-10.83; ≥25: HR = 3.85, 95% CI = 1.80 to 8.26). Heavy former (vs current) smokers had 39.1% lower lung cancer risk within five YSQ. Among all former smokers, 40.8% of lung cancers occurred after more than 15 YSQ.

Conclusions

Among heavy former smokers, lung cancer risk drops within five YSQ relative to continuing smokers, yet it remains more than threefold higher than never smokers after 25 YSQ. Four of ten lung cancers occurred in former smokers with more 15 YSQ, beyond the screening window of the current guideline.

Exposure-Lag-Response in Longitudinal Studies: Application of Distributed-Lag Nonlinear Models in an Occupational Cohort

Prolonged exposures can have complex relationships with health outcomes, as timing, duration, and intensity of exposure are all potentially relevant. Summary measures such as cumulative exposure or average intensity of exposure may not fully capture these relationships. We applied penalized and unpenalized distributed-lag nonlinear models (DLNMs) with flexible exposure-response and lag-response functions in order to examine the association between crystalline silica exposure and mortality from lung cancer and nonmalignant respiratory disease in a cohort study of 2,342 California diatomaceous earth workers followed during 1942–2011. We also assessed associations using simple measures of cumulative exposure assuming linear exposure-response and constant lag-response. Measures of association from DLNMs were generally higher than those from simpler models. Rate ratios from penalized DLNMs corresponding to average daily exposures of 0.4 mg/m³ during lag years 31–50 prior to the age of observed cases were 1.47 (95% confidence interval (CI): 0.92, 2.35) for lung cancer mortality and 1.80 (95% CI: 1.14, 2.85) for nonmalignant respiratory disease mortality. Rate ratios from the simpler models for the same exposure scenario were 1.15 (95% CI: 0.89, 1.48) and 1.23 (95% CI: 1.03, 1.46), respectively. Longitudinal cohort studies of prolonged exposures and chronic health outcomes should explore methods allowing for flexibility and nonlinearities in the exposure-lag-response.

[Is reduction of tobacco consumption associated with reduced risk of cardiovascular and pulmonary mortality and morbidity?]

INTRODUCTION

Smokers without an intention to completely quit smoking often try to reduce their daily tobacco consumption. However, smoking reduction is not associated with reduced risk of all-cause mortality. The aim of this systematic literature review of data was to expose relations between reduction of daily tobacco consumption and a potential decrease in the risks of cardiovascular and pulmonary mortality and morbidity.

METHOD

Medline, on the period 1980-2018 with the following keywords: "smoking reduction", "harm reduction", "mortality", "morbidity", "cardiovascular disease*", myocardial infarction", "coronar*", "stroke", "lung cancer", "COPD", "chronic obstructive pulmonary disease", "asthma", "pulmonary disease*" and "respiratory disease" limits "title/abstract"; the selected languages were English or French. Among 158 articles, 32 abstracts have given use to a dual reading to select 19 studies.

RESULTS

Reduction of daily tobacco consumption by at least 50% is not associated with (1) reduced risk of cardiovascular mortality and morbidity and (2) reduced risk of lung cancer mortality. Results of studies on the risk of lung cancer morbidity are conflicting. Smoking reduction by at least 50% has no or little effect on the incidence of chronic obstructive pulmonary disease (COPD) and FEV1 decline. In asthmatic patients, smoking reduction is associated with small improvement for night use of short acting beta2-agonists, doses of inhaled corticosteroids and bronchial hyper-reactivity.

CONCLUSION

Smoking cessation is the only effective strategy to reduce the harm caused by tobacco smoking. This finding should lead clinicians to offer support to smokers in order to assist them to completely quit smoking.

The diversity of myeloid immune cells shaping wound repair and fibrosis in the lung

In healthy circumstances the immune system coordinates tissue repair responses in a tight balance that entails efficient inflammation for removal of potential threats, proper wound closure, and regeneration to regain tissue function. Pathological conditions, continuous exposure to noxious agents, and even ageing can dysregulate immune responses after injury. This dysregulation can lead to a chronic repair mechanism known as fibrosis. Alterations in wound healing can occur in many organs, but our focus lies with the lung as it requires highly regulated immune and repair responses with its continuous exposure to airborne threats. Dysregulated repair responses can lead to pulmonary fibrosis but the exact reason for its development is often not known. Here, we review the diversity of innate immune cells of myeloid origin that are involved in tissue repair and we illustrate how these cell types can contribute to the development of pulmonary fibrosis. Moreover, we briefly discuss the effect of age on innate immune responses and therefore on wound healing and we conclude with the implications of current knowledge on the avenues for future research.

Are healthy smokers really healthy?

Cigarette smoke contains more than 4500 chemicals which have toxic, mutagenic and carcinogenic effects. Strong evidences have shown that current smokers take a significantly higher risk of cardiovascular diseases, chronic obstructive pulmonary disease (COPD) and lung cancer than nonsmokers. However, less attention has been paid to the smoking induced abnormalities in the individuals defined as healthy smokers who are normal with spirometry, radiographic images, routine physical exam and categorized as healthy control group in many researches. Actually, 'healthy smokers' are not healthy. This narrative review focuses on the smoking related pathophysiologic changes mainly in the respiratory system of healthy smokers, including inflammation and immune changes, genetic alterations, structural changes and pulmonary dysfunction.

Benzo(a)pyrene induced structural and functional modifications in lung cystatin

Cystatins are thiol proteinase inhibitors ubiquitously present in the mammalian body. They serve a protective function to regulate the activities of endogenous proteinases, which may cause uncontrolled proteolysis and damage. In the present study, the effect of benzo(a)pyrene [BaP] on lung cystatin was studied to explore the hazardous effects of environmental pollutant on structural and functional integrity of the protein. The basic binding interaction was studied by UV-absorption, FT-IR, and fluorescence spectroscopy. The enhancement of total protein fluorescence with a red shift of 5 nm suggests structural scratch of lung cystatin by benzo(a)pyrene. Further, ANS binding studies reaffirm the unfolding of the thiol protease inhibitor (GLC-I) after treating with benzo(a)pyrene. The results of FT-IR spectroscopy reflect perturbation of the secondary conformation (alpha-helix to β-sheet) in goat lung cystatin on interaction with BaP. Finally, functional inactivation of cystatin on association with BaP was checked by its papain inhibitory activity. Benzo(a)pyrene (10 μM) caused complete inactivation of goat lung cystatin. Benzo(a)pyrene-induced loss of structure and function in the thiol protease inhibitor could provide a caution for lung injury caused by the pollutants and smokers.

Systematic review with meta-analysis of the epidemiological evidence in the 1900s relating smoking to lung cancer

BACKGROUND

Smoking is a known lung cancer cause, but no detailed quantitative systematic review exists. We summarize evidence for various indices.

METHODS

Papers published before 2000 describing epidemiological studies involving 100+ lung cancer cases were obtained from Medline and other sources. Studies were classified as principal, or subsidiary where cases overlapped with principal studies. Data were extracted on design, exposures, histological types and confounder adjustment. RRs/ORs and 95% CIs were extracted for ever, current and ex smoking of cigarettes, pipes and cigars and indices of cigarette type and dose-response. Meta-analyses and meta-regressions investigated how relationships varied by study and RR characteristics, mainly for outcomes exactly or closely equivalent to all lung cancer, squamous cell carcinoma ("squamous") and adenocarcinoma ("adeno").

RESULTS

287 studies (20 subsidiary) were identified. Although RR estimates were markedly heterogeneous, the meta-analyses demonstrated a relationship of smoking with lung cancer risk, clearly seen for ever smoking (random-effects RR 5.50, CI 5.07-5.96) current smoking (8.43, 7.63-9.31), ex smoking (4.30, 3.93-4.71) and pipe/cigar only smoking (2.92, 2.38-3.57). It was stronger for squamous (current smoking RR 16.91, 13.14-21.76) than adeno (4.21, 3.32-5.34), and evident in both sexes (RRs somewhat higher in males), all continents (RRs highest for North America and lowest for Asia, particularly China), and both study types (RRs higher for prospective studies). Relationships were somewhat stronger in later starting and larger studies. RR estimates were similar in cigarette only and mixed smokers, and similar in smokers of pipes/cigars only, pipes only and cigars only. Exceptionally no increase in adeno risk was seen for pipe/cigar only smokers (0.93, 0.62-1.40). RRs were unrelated to mentholation, and higher for non-filter and handrolled cigarettes. RRs increased with amount smoked, duration, earlier starting age, tar level and fraction smoked and decreased with time quit. Relationships were strongest for small and squamous cell, intermediate for large cell and weakest for adenocarcinoma. Covariate-adjustment little affected RR estimates.

CONCLUSIONS

The association of lung cancer with smoking is strong, evident for all lung cancer types, dose-related and insensitive to covariate-adjustment. This emphasises the causal nature of the relationship. Our results quantify the relationships more precisely than previously.

A risk model for lung cancer incidence

Risk models for lung cancer incidence would be useful for prioritizing individuals for screening and participation in clinical trials of chemoprevention. We present a risk model for lung cancer built using prospective cohort data from a general population which predicts individual incidence in a given time period. We build separate risk models for current and former smokers using 169,035 ever smokers from the multicenter European Prospective Investigation into Cancer and Nutrition (EPIC) and considered a model for never smokers. The data set was split into independent training and test sets. Lung cancer incidence was modeled using survival analysis, stratifying by age started smoking, and for former smokers, also smoking duration. Other risk factors considered were smoking intensity, 10 occupational/environmental exposures previously implicated with lung cancer, and single-nucleotide polymorphisms at two loci identified by genome-wide association studies of lung cancer. Individual risk in the test set was measured by the predicted probability of lung cancer incidence in the year preceding last follow-up time, predictive accuracy was measured by the area under the receiver operator characteristic curve (AUC). Using smoking information alone gave good predictive accuracy: the AUC and 95% confidence interval in ever smokers was 0.843 (0.810-0.875), the Bach model applied to the same data gave an AUC of 0.775 (0.737-0.813). Other risk factors had negligible effect on the AUC, including never smokers for whom prediction was poor. Our model is generalizable and straightforward to implement. Its accuracy can be attributed to its modeling of lifetime exposure to smoking.

A Review of Hypothesized Determinants Associated with Bighorn Sheep (Ovis canadensis) Die-Offs

Multiple determinants have been hypothesized to cause or favor disease outbreaks among free-ranging bighorn sheep (Ovis canadensis) populations. This paper considered direct and indirect causes of mortality, as well as potential interactions among proposed environmental, host, and agent determinants of disease. A clear, invariant relationship between a single agent and field outbreaks has not yet been documented, in part due to methodological limitations and practical challenges associated with developing rigorous study designs. Therefore, although there is a need to develop predictive models for outbreaks and validated mitigation strategies, uncertainty remains as to whether outbreaks are due to endemic or recently introduced agents. Consequently, absence of established and universal explanations for outbreaks contributes to conflict among wildlife and livestock stakeholders over land use and management practices. This example illustrates the challenge of developing comprehensive models for understanding and managing wildlife diseases in complex biological and sociological environments.

Cigarette smoking and lung cancer in women: results of the French ICARE case-control study

BACKGROUND

The incidence of female lung cancer in developed countries has been increasing since 1950. In order to have recent and reliable data on the association between cigarette smoking and the risk of lung cancer in women, we analysed cases from a French population-based case-control study.

METHODS

The ICARE study is a multicenter case-control study on respiratory cancers (lung and UADT cancers), set up in 10 départements that include a general cancer registry. We included 648 women lung cancer cases up to 76 years of age, with a histologically confirmed primary lung cancer. The 775 controls were randomly selected from the general population and frequency-matched with cases by age and département.

RESULTS

Overall, smoking cigarettes at some time was associated with a 8-fold increase in lung cancer risk (OR=8.2, 95% CI 6.0-11.4). A dose-response relationship was observed as a function of duration, intensity and pack-years. Using restricted splines cubic models, we have shown that intensity dose-response departed significantly from linearity while the risk increased linearly with duration and decreased linearly with time since cessation. The following characteristics were associated with a higher relative risk: smoke inhalation, smoking non-filter cigarettes, smoking dark tobacco cigarettes and starting at a young age. In addition, duration, intensity and time since cessation was significantly related with histological type. This was not the case for characteristics such as the use of a filter or not, the inhalation pattern, or the type of tobacco smoked. The proportion of lung cancer cases attributable to cigarette smoking was 55% (95% CI: [47-63%]).

CONCLUSIONS

Our results confirm that cigarette smoking is by far the most important cause of the current epidemic of lung cancer among French women and that the most important smoking-related variables for varying the risk of lung cancer are the duration, the intensity and the time since cessation.

Genetic variants and risk of lung cancer in never smokers: a genome-wide association study

BACKGROUND

Lung cancer in individuals who have never smoked tobacco products is an increasing medical and public-health issue. We aimed to unravel the genetic basis of lung cancer in never smokers.

METHODS

We did a four-stage investigation. First, a genome-wide association study of single nucleotide polymorphisms (SNPs) was done with 754 never smokers (377 matched case-control pairs at Mayo Clinic, Rochester, MN, USA). Second, the top candidate SNPs from the first study were validated in two independent studies among 735 (MD Anderson Cancer Center, Houston, TX, USA) and 253 (Harvard University, Boston, MA, USA) never smokers. Third, further replication of the top SNP was done in 530 never smokers (UCLA, Los Angeles, CA, USA). Fourth, expression quantitative trait loci (eQTL) and gene-expression differences were analysed to further elucidate the causal relation between the validated SNPs and the risk of lung cancer in never smokers.

FINDINGS

44 top candidate SNPs were identified that might alter the risk of lung cancer in never smokers. rs2352028 at chromosome 13q31.3 was subsequently replicated with an additive genetic model in the four independent studies, with a combined odds ratio of 1.46 (95% CI 1.26-1.70, p=5.94x10(-6)). A cis eQTL analysis showed there was a strong correlation between genotypes of the replicated SNPs and the transcription level of the gene GPC5 in normal lung tissues (p=1.96x10(-4)), with the high-risk allele linked with lower expression. Additionally, the transcription level of GPC5 in normal lung tissue was twice that detected in matched lung adenocarcinoma tissue (p=6.75x10(-11)).

INTERPRETATION

Genetic variants at 13q31.3 alter the expression of GPC5, and are associated with susceptibility to lung cancer in never smokers. Downregulation of GPC5 might contribute to the development of lung cancer in never smokers.

FUNDING

US National Institutes of Health; Mayo Foundation.

Lung cancer mortality at a UK tin smelter

BACKGROUND

An earlier study of mortality among male former employees at a tin smelter in Humberside, UK, had identified excess mortality from lung cancer, which appeared to be associated with occupational exposure.

AIMS

The aim of the present study was to investigate the relationship between lung cancer mortality and quantitative measures of exposure.

METHODS

Using available records of occupational hygiene measurements, we established exposure matrices for arsenic, cadmium, lead, antimony and polonium-210 ((210)Po), covering the main process areas of the smelter. We established work histories from personnel record cards for the previously defined cohort of 1462 male employees. Three different methods of extrapolation were used to assess exposures prior to 1972, when no measurement results were available. Lung cancer mortality was examined in relation to cumulative inhalation exposure by Poisson regression analysis.

RESULTS

No significant associations could be found between lung cancer mortality and simple cumulative exposure to any of the substances studied. When cumulative exposures were weighted according to time since exposure and attained age, significant associations were found between lung cancer mortality and exposures to arsenic, lead and antimony.

CONCLUSIONS

The excess of lung cancer mortality in the cohort can most plausibly be explained if arsenic is the principal occupational carcinogen (for which the excess relative risk diminishes with time since exposure and attained age) and if there is a contribution to excess mortality from an enhanced prevalence of smoking within the cohort. The implications of the dose-response for arsenic exposure for risk estimation merit further consideration.

The California Tobacco Control Program's effect on adult smokers: (2) Daily cigarette consumption levels

OBJECTIVE

To investigate the association of the California Comprehensive Tobacco Control Program with self-reported population trends of cigarette consumption during 1992-2002.

SETTING AND PARTICIPANTS

Participants were non-Hispanic white daily smokers (aged 20-64 years, n = 24 317) from the Tobacco Use Supplements to the Current Population Survey (1992-2002). We compared age-specific trends in consumption among daily smokers in three groups of states with differing tobacco control initiatives: California (CA; high cigarette price/comprehensive programme), New York and New Jersey (high cigarette price/no comprehensive programme), and tobacco-growing states (TGS; low cigarette price/no comprehensive programme).

RESULTS

There was a general decline in cigarette consumption across all age groups in each category of states between 1992 and 2002, except the oldest age group in the TGS. The largest annual decline in the average number of cigarettes per day was observed among daily smokers in CA who were aged > or = 35 years (-0.41 cigarettes/day/year (95% CI -0.52 to -0.3)). This rate was significantly higher than the -0.22 cigarettes/day/year (95% CI -0.3 to -0.16; p<0.02) observed in same-age daily smokers from New York and New Jersey, and significantly higher than the rate in same-age daily smokers from the TGS (-0.15 cigarettes/day/year (95% CI -0.22 to -0.08; p<0.002)). There were no significant differences across state groups in the decline observed in daily smokers aged 20-34 years. In 2002, only 12% of daily smokers in CA smoked more than a pack per day, which was significantly lower than the 17% in New York and New Jersey, which again was significantly lower than the 25% in the TGS.

CONCLUSIONS

The California Tobacco Control Program was associated with significant declines in cigarette consumption among daily smokers aged > or = 35 years of age, which in turn should lead to declines in tobacco-related health effects. The decline in consumption among young adult smokers was a national trend.

What contributed to the major decline in per capita cigarette consumption during California's comprehensive tobacco control programme?

OBJECTIVES

California experienced a notable decline in per capita cigarette consumption during its comprehensive tobacco control programme. This study examines what proportion of the decline occurred from: (1) fewer ever smokers in the population, (2) more ever smokers quitting, and (3) current smokers smoking less.

DESIGN, SUBJECTS

Per capita cigarette consumption computed from cigarette sales and from adult respondents to the large, cross-sectional, population-based California Tobacco Surveys of 1990 (n = 24,296), 1996 (n = 18,616) and 2002 (n = 20,525) were examined for similar trends.

MAIN OUTCOME MEASURE

Changes (period 1: 1990-1996; period 2: 1996-2002) in per capita cigarette consumption from self-reported survey data were partitioned for the entire population and for demographic subgroups into the three components mentioned above.

RESULTS

In periods 1 and 2, most of the decline in per capita cigarette consumption for the population as a whole was from current smokers smoking less followed by a reduction in ever smokers. The decline from smokers smoking less was particularly evident among young adults (18-29 years) in period 1. While the portion of the decline due to quitting in the entire population in period 1 was negligible, in period 2 it accounted for 22% of the total per capita decline. The decline from quitting in period 2 was mostly observed among women.

CONCLUSIONS

Rather than near-term benefits from smokers quitting, population health benefits from reduced per capita cigarette consumption will likely occur over the longer term from fewer people becoming ever smokers, and more less-addicted smokers eventually quitting successfully.

Does smoking reduction increase future cessation and decrease disease risk? A qualitative review

This review examines whether reduction in smoking among smokers not currently interested in quitting (a) undermines or promotes future smoking cessation or (b) decreases the risks of developing smoking-related diseases. Systematic computer searches and other methods located 19 studies examining reduction and subsequent cessation and 10 studies examining reduction and disease risk. Because of the heterogeneity of methods and results, a meta-analysis could not be undertaken. None of 19 studies found that reduction undermined future cessation, and 16 found that reduction was associated with greater future cessation, including the two randomized trials of reduction versus nonreduction. The 10 trials of disease risk found conflicting results, and none was an adequate test. We conclude that (a) smoking reduction increases the probability of future cessation and (b) whether smoking reduction decreases the risks of smoking-related diseases has not been adequately tested.

Quality of life in newly diagnosed patients with lung cancer in a developing country: is it important?

There are no data regarding quality of life (QoL) assessments in lung cancer in developing countries like India. Quality of life was evaluated in 76 newly diagnosed lung cancer patients by using the World Health Organization Quality of Life questionnaire in Hindi (WHOQoL-Bref) (men 87%). The mean age was 55 years (SD = 10). Cough, dyspnoea, chest pain and haemoptysis were present in 83%, 72%, 66% and 43% of patients respectively. The median duration of symptoms was 5.9 months (range 1-13). Eighty-nine per cent had non-small cell lung cancer. The median pack-years smoked was 23 (range 0.5-88). Most patients (53%) had a Karnofsky's Performance Status (KPS) of 70 and 83% had stage III or IV disease. Quality of life did not correlate with age, gender, presence or duration of symptoms, histological type, stage of disease or degree of smoking. The physical and psychological domains of QoL correlated significantly with the KPS (P = 0.001 and P = 0.01 respectively). Patients with a KPS of 80 had better physical (P < 0.001), psychological (P < 0.01) and social (P < 0.05) QoL than those with a KPS of 70. In conclusion, patients with lung cancer in a developing country like India have an unsatisfactory QoL. The Karnofsky's Performance Scale is a simple and reliable surrogate marker for assessing QoL in these patients. Larger multi-centric studies may help in providing a more comprehensive evaluation of the effect of various demographic and clinical variables on QoL in this setting.

Smoking cessation and lung cancer mortality in a cohort of middle-aged Canadian women

PURPOSE

To determine the impact of smoking cessation on lung cancer mortality among women.

METHODS

Survival analysis is used to assess the effect of smoking cessation on lung cancer death in the dietary cohort of 49,165 women aged 40 to 59 years enrolled in the Canadian National Breast Screening Study.

RESULTS

During an average of 10.3 years of follow-up, 106 women died of lung cancer. The risk of lung cancer mortality among women who quit before age 50 (HR=0.26; 95% CI, 0.13-0.55 among women who quit at ages 40-49) or quit in the previous 10 years (HR=0.39; 95% CI, 0.22-0.69) is substantially lower than the risk among current smokers. Women who quit after age 40 or have quit for less than 20 years are at substantially higher risk of lung cancer mortality compared with never smokers. Both duration of smoking cessation and age at quitting have independent effects on lung cancer mortality, after controlling for number of cigarettes smoked per day and number of years smoked, as well as other potential confounding variables.

CONCLUSION

These findings suggest that programs and policies to promote early cessation of smoking and prevention of relapse should be a public health priority.

Does increased cigarette consumption nullify any reduction in lung cancer risk associated with low-tar filter cigarettes?

Epidemiological data suggest that smoking filter and lower tar cigarettes is associated with less lung cancer risk than is smoking plain and higher tar cigarettes. A recent National Cancer Institute monograph claimed these apparent benefits of lower delivery products may be illusory if relative risks are adjusted for daily consumption, and switching leads to "compensation" for reduced nicotine intake by increasing numbers of cigarettes smoked. To investigate this, we compared relative risks unadjusted and adjusted for daily cigarette consumption. Overall estimates of the filter/plain relative risk, using random-effects meta-analysis, were 0.61 (95%confidence interval 0.54 to 0.70) for unadjusted data and 0.66 (0.58 to 0.76) for adjusted data. The lower tar/higher tar relative risk was estimated as 0.60 (0.45 to 0.81) for unadjusted data and 0.73 (0.64 to 0.83) for adjusted data. The risk reductions were clearly seen regardless of gender, study location, period, or design, and when only studies providing both unadjusted and adjusted estimates were considered. Whether or not relative risk estimates are adjusted for cigarette consumption is not crucial to the conclusion of a clear advantage to filter cigarettes and tar reduction. Data on "compensation" for amount smoked were reviewed and any increase following switching to reduced-tar-yield cigarettes was shown to be quite small. Other biases in the epidemiology are also discussed, and we conclude that the apparent advantage to reduced-tar-delivery products is real and likely to be a marked underestimate of the reduction in lung cancer risk from lifetime smoking of low-tar cigarettes.

A flexible modeling approach to estimating the component effects of smoking behavior on lung cancer

OBJECTIVE

Despite the established causal association between cigarette smoking and lung cancer, the relative contributions of age started, duration, years since quitting, and daily amount smoked have not been well characterized. We estimated the contribution of each of these aspects of smoking behavior.

STUDY DESIGN AND SETTING

A case-control study was conducted in Montreal on the etiology of lung cancer. There were 640 cases and 938 control subjects for whom lifetime smoking histories were collected. We used generalized additive models, incorporating cubic smoothing splines to model nonlinear effects of various smoking variables. We adopted a multistep approach to deal with the multicollinearity among time-related variables.

RESULTS

The main findings are that (1) risk increases independently by daily amount and by duration; (2) among current smokers, lung cancer risk doubles for every 10 cigarettes per day up to 30 to 40 cigarettes per day and tails off thereafter; (3) among ex-smokers, the odds ratio decreases with increasing time since quitting, the rate of decrease being sharper among heavy smokers than among light smokers; and (4) absolute risks demonstrate the dramatic public health benefits of long-term smoking cessation.

CONCLUSION

Our results reinforce some previous findings on this issue.

Cigarette smoking and testicular cancer

The purpose of this study was to determine the relation between testicular cancer and cigarette smoking. Data were collected between 1995 and 1996 in Ontario, Canada, as part of the Enhanced Cancer Surveillance Study. Pack-years and years of smoking were examined among all subjects (212 cases and 252 controls) and former and current smokers. Years since quitting and age at smoking initiation were examined among former and current smokers only. Independent of smoking status, significant associations were noted among those who smoked between 12 and 24 pack-years [odds ratio (OR) = 1.96 (95% confidence interval (CI): 1.04-3.69), relative to nonsmokers] or greater [>24 pack-years, OR = 2.31 (95% CI: 1.12-4.77), relative to nonsmokers], and among those who smoked >21 years [OR = 3.18 (95% CI: 1.32-7.64), relative to nonsmokers]. Quitting smoking was not found to result in a reduction of risk. No association was observed for smoking at adolescence relative to a later period. Results from the study suggest that cigarette smoking exerts an adverse influence on testicular cancer risk that is not mitigated by smoking cessation and not altered by age at initiation.

Cigarette tar yields in relation to mortality from lung cancer in the cancer prevention study II prospective cohort, 1982-8

OBJECTIVE

To assess the risk of lung cancer in smokers of medium tar filter cigarettes compared with smokers of low tar and very low tar filter cigarettes.

DESIGN

Analysis of the association between the tar rating of the brand of cigarette smoked in 1982 and mortality from lung cancer over the next six years. Multivariate proportional hazards analyses used to assess hazard ratios, with adjustment for age at enrollment, race, educational level, marital status, blue collar employment, occupational exposure to asbestos, intake of vegetables, citrus fruits, and vitamins, and, in analyses of current and former smokers, for age when they started to smoke and number of cigarettes smoked per day.

SETTING

Cancer prevention study II (CPS-II).

PARTICIPANTS

364 239 men and 576 535 women, aged > or = 30 years, who had either never smoked, were former smokers, or were currently smoking a specific brand of cigarette when they were enrolled in the cancer prevention study.

MAIN OUTCOME MEASURE

Death from primary cancer of the lung among participants who had never smoked, former smokers, smokers of very low tar (< or = 7 mg tar/cigarette) filter, low tar (8-14 mg) filter, high tar (> or = 22 mg) non-filter brands and medium tar conventional filter brands (15-21 mg).

RESULTS

Irrespective of the tar level of their current brand, all current smokers had a far greater risk of lung cancer than people who had stopped smoking or had never smoked. Compared with smokers of medium tar (15-21 mg) filter cigarettes, risk was higher among men and women who smoked high tar (> or = 22 mg) non-filter brands (hazard ratio 1.44, 95% confidence interval 1.20 to 1.73, and 1.64, 1.26 to 2.15, respectively). There was no difference in risk among men who smoked brands rated as very low tar (1.17, 0.95 to 1.45) or low tar (1.02, 0.90 to 1.16) compared with those who smoked medium tar brands. The same was seen for women (0.98, 0.80 to 1.21, and 0.95, 0.82 to 1.11, respectively).

CONCLUSION

The increase in lung cancer risk is similar in people who smoke medium tar cigarettes (15-21 mg), low tar cigarettes (8-14 mg), or very low tar cigarettes (< or = 7 mg). Men and women who smoke non-filtered cigarettes with tar ratings > or = 22 mg have an even higher risk of lung cancer.

Variations in lung cancer risk among smokers

BACKGROUND

Although there is no proven benefit associated with screening for lung cancer, screening programs are attracting many individuals who perceive themselves to be at high risk due to smoking. We sought to determine whether the risk of lung cancer varies predictably among smokers.

METHODS

We used data on 18 172 subjects enrolled in the Carotene and Retinol Efficacy Trial (CARET)-a large, randomized trial of lung cancer prevention-to derive a lung cancer risk prediction model. Model inputs included the subject's age, sex, asbestos exposure history, and smoking history. We assessed the model's calibration by comparing predicted and observed rates of lung cancer across risk deciles and validated it by assessing the extent to which a model estimated on data from five CARET study sites could predict events in the sixth study site. We then applied the model to evaluate the risk of lung cancer among smokers enrolled in a study of lung cancer screening with computed tomography (CT).

RESULTS

The model was internally valid and well calibrated. Ten-year lung cancer risk varied greatly among participants in the CT study, from 15% for a 68-year-old man who has smoked two packs per day for 50 years and continues to smoke, to 0.8% for a 51-year-old woman who smoked one pack per day for 28 years before quitting 9 years earlier. Even among the subset of CT study participants who would be eligible for a clinical trial of cancer prevention, risk varied greatly.

CONCLUSIONS

The risk of lung cancer varies widely among smokers. Accurate risk prediction may help individuals who are contemplating voluntary screening to balance the potential benefits and risks. Risk prediction may also be useful for researchers designing clinical trials of lung cancer prevention.

Lung cancer risk reduction after smoking cessation: observations from a prospective cohort of women

PURPOSE

We conducted this study because the duration of excess lung cancer risk among former smokers has been inconsistently reported, doubt has been raised regarding the population impact of smoking cessation, and differential risk reduction by histologic cell type after smoking cessation needs to be confirmed.

METHODS

The Iowa Women's Health Study is a prospective cohort study of 41,836 Iowa women aged 55 to 69 years. In 1986, mailed questionnaires were used to collect detailed smoking history. Age-adjusted lung cancer incidence through 1999 was analyzed according to years of smoking abstinence. Relative risks were estimated using Cox regression analysis.

RESULTS

There were 37,078 women in the analytic cohort. Compared with the never smokers, former smokers had an elevated lung cancer risk (relative risk, 6.6; 95% confidence interval, 5.0 to 8.7) up to 30 years after smoking cessation for all former smokers. However, a beneficial effect of smoking cessation was observed among recent and distant former smokers. The risk of adenocarcinoma remained elevated up to 30 years for both former heavier and former lighter smokers.

CONCLUSION

The risk for lung cancer is increased for both current and former smokers compared with never smokers and declines for former smokers with increasing duration of abstinence. The decline in excess lung cancer risk among former smokers is prolonged compared with other studies, especially for adenocarcinoma and for heavy smokers, suggesting that more emphasis should be placed on smoking prevention and lung cancer chemoprevention.

Household stove improvement and risk of lung cancer in Xuanwei, China

BACKGROUND

Lung cancer rates in rural Xuanwei County, Yunnan Province, are among the highest in China. Residents traditionally burned "smoky" coal in unvented indoor firepits that generated very high levels of air pollution. Since the 1970s, most residents have changed from firepits to stoves with chimneys. This study assessed whether lung cancer incidence decreased after this stove improvement.

METHODS

A cohort of 21 232 farmers, born from 1917 through 1951, was followed retrospectively from 1976 through 1992. All subjects were users of smoky coal who had been born into homes with unvented firepits. During their lifetime, 17 184 subjects (80.9%) changed permanently to stoves with chimneys. A hospital record search detected 1384 cases of lung cancer (6.5%) during follow-up. Associations of stove improvement with lung cancer incidence were analyzed with product-limit plots and multivariable Cox models. In 1995, indoor concentrations of airborne particles and benzo[a]pyrene were compared in Xuanwei homes during smoky coal burning in stoves with chimneys and in unvented stoves or firepits.

RESULTS

A long-term reduction in lung cancer incidence was noted after stove improvement. In Cox models, risk ratios (RRs) for lung cancer after stove improvement were 0.59 (95% confidence interval [CI] = 0.49 to 0.71) in men and 0.54 (95% CI = 0.44 to 0.65) in women (for both, P<.001). Incidence reduction became unequivocal about 10 years after stove improvement. Levels of indoor air pollution during burning with chimneys were less than 35% of levels during unvented burning.

CONCLUSION

Changing from unvented to vented stoves appears to benefit the health of people in China and may do so in other developing countries as well.

Cardiorespiratory fitness and smoking-related and total cancer mortality in men

PURPOSE

We investigated the association between cardiorespiratory fitness and smoking-related, nonsmoking-related, and total cancer mortality in men.

METHODS

We followed 25,892 men, age 30-87 yr, who had a preventive medical evaluation, including a maximal exercise test and self-reported health habits. There were 335 cancer deaths (133 from smoking-related cancer, 202 from nonsmoking-related cancer) during an average of 10 yr of follow-up (259,124 man-yr).

RESULTS

After adjustment for age, examination year, smoking habits, alcohol intake, body mass index, and diabetes mellitus, there was an inverse association between cardiorespiratory fitness levels and smoking-related (P < 0.001 for trend), nonsmoking-related (P = 0.001 for trend), and total cancer mortality (P < 0.001 for trend). Moderate and high levels of cardiorespiratory fitness were associated with lower risk of smoking-related and nonsmoking-related cancer mortality when compared with low fitness in men. We also observed that smoking-related mortality rates were progressively lower across low, moderate, and high fitness groups in former (P = 0.06 for trend) and current (P = 0.04 for trend) smokers.

CONCLUSION

We conclude that cardiorespiratory fitness may provide protection against cancer mortality in men.

Lymphocyte DNA damage in elevator manufacturing workers in Guangzhou, China

AIMS

To study the effect of smoking, passive smoking, alcohol drinking, and occupational exposure to low level of benzene on DNA strand breaks in elevator manufacturing workers in Guangzhou, China.

METHODS

Three hundred and fifty-nine workers (252 men and 107 women) of a modern elevator manufacturing factory, 205 were from production departments and 154 from managerial department. Information on the workers' health conditions, smoking, passive smoking, alcohol consumption and occupational exposure history was collected by personal interview. Lymphocyte DNA damage was measured by the Comet assay.

RESULTS

None of the women smoked and 20.6% of the men were daily smokers. In non-smokers, the prevalence of passive smoking at work was 25% for men and 11.2% for women, and at home, 37.8 and 48.6%, respectively. Smoking significantly increased tail moment (P<0.001). Daily smokers had the largest tail moment (geometric mean, 95% CI) (0.93 microm (0.81-0.94)), followed by occasional smokers (0.76 microm (0.59-0.95)), ex-smokers (0.70 microm (0.58-0.85)), and never smokers (0.56 microm (0.53-0.60)). Tail moment increased significantly with daily tobacco consumption (cigarettes per day) (r=0.26, P<0.001) after adjusting for age, gender, occupational exposure, passive smoking, and drinking. Analysis of covariance (ANCOVA) showed that smoking (P<0.001), passive smoking at home (P=0.026), occupational exposure (P<0.001), male gender (P<0.001), and age (P=0.001) had independent effects on tail moment, whereas passive smoking at work and alcohol drinking had no significant effect.

CONCLUSIONS

Smoking, passive smoking at home, male gender, age and occupational exposure independently increased lymphocyte DNA strand breaks. The presence of excess DNA damage under low level of occupational exposure to benzene or other solvents suggest that the current allowance concentrations may not be safe to prevent genotoxicity.

Simple office spirometry

Spirometric measurements are as fundamental to medicine as are measurements of pulse, blood pressure, temperature, height, and weight. Spirometric measurements should be considered important vital signs. Any deviations from "normal" measurements can point primary care physicians toward the use of behavioral modification or effective pharmacologic agents to prevent or forestall their patients' premature morbidity and mortality from many disease states, including premature deaths from all causes.

Trends in incidence and prognosis of the histological subtypes of lung cancer in North America, Australia, New Zealand and Europe

BACKGROUND

Since the incidence of the histological subtypes of lung cancer in industrialised countries has changed dramatically over the last two decades, we reviewed trends in the incidence and prognosis in North America, Australia, New Zealand and Europe, according to period of diagnosis and birth cohort and summarized explanations for changes in mortality.

METHODS

Review of the literature based on a computerised search (Medline database 1966-2000).

RESULTS

Although the incidence of lung cancer has been decreasing since the 1970s/1980s among men in North America, Australia, New Zealand and north-western Europe, the age-adjusted rate continues to increase among women in these countries, and among both men and women in southern and eastern Europe. These trends followed changes in smoking behaviour. The proportion of adenocarcinoma has been increasing over time; the most likely explanation is the shift to low-tar filter cigarettes during the 1960s and 1970s. Despite improvement in both the diagnosis and treatment, the overall prognosis for patients with non-small-cell lung cancer hardly improved over time. In contrast, the introduction and improvement of chemotherapy since the 1970s gave rise to an improvement in - only short-term (<2 years) - survival for patients with small-cell lung cancer.

CONCLUSIONS

The epidemic of lung cancer is not over yet, especially in southern and eastern Europe. Except for short-term survival of small cell tumours, the prognosis for patients with lung cancer has not improved significantly.

Health impact of "reduced yield" cigarettes: a critical assessment of the epidemiological evidence

Cigarettes with lower machine measured "tar" and nicotine yields have been marketed as "safer" than high tar products over the last four decades, but there is conflicting evidence about the impact of these products on the disease burden caused by smoking. This paper critically examines the epidemiological evidence relevant to the health consequences of "reduced yield" cigarettes. Some epidemiological studies have found attenuated risk of lung cancer but not other diseases, among people who smoke "reduced yield" cigarettes compared to smokers of unfiltered, high yield products. These studies probably overestimate the magnitude of any association with lung cancer by over adjusting for the number of cigarettes smoked per day (one aspect of compensatory smoking), and by not fully considering other differences between smokers of "high yield" and "low yield" cigarettes. Selected cohort studies in the USA and UK show that lung cancer risk continued to increase among older smokers from the 1950s to the 1980s, despite the widespread adoption of lower yield cigarettes. The change to filter tip products did not prevent a progressive increase in lung cancer risk among male smokers who began smoking during and after the second world war compared to the first world war era smokers. National trends in vital statistics data show declining lung cancer death rates in young adults, especially males, in many countries, but the extent to which this is attributable to "reduced yield" cigarettes remains unclear. No studies have adequately assessed whether health claims used to market "reduced yield" cigarettes delay cessation among smokers who might otherwise quit, or increase initiation among non-smokers. There is no convincing evidence that past changes in cigarette design have resulted in an important health benefit to either smokers or the whole population. Tobacco control policies should not allow changes in cigarette design to subvert or distract from interventions proven to reduce the prevalence, intensity, and duration of smoking.

Analysis of exposure-time-response relationships using a spline weight function

To examine the time-dependent effects of exposure histories on disease, we estimate a weight function within a generalized linear model. The shape of the weight function, which is modeled as a cubic B-spline, gives information about the impact of exposure increments at different times on disease risk. The method is evaluated in a simulation study and is applied to data on smoking histories and lung cancer from a recent case-control study in Germany.

The use of sliding time windows for the exploratory analysis of temporal effects of smoking histories on lung cancer risk

To examine the time-dependent effects of exposure histories on disease we use sliding time windows as an exploratory alternative to the analysis of variables like time since last exposure and duration of exposure. The method fits a series of risk models which contain total cumulative exposure and an additional covariate for exposures received during fixed time intervals. Characteristics of the fitted models provide insight into the influence of exposure increments at different times on disease risk. A simulation study is performed to check the validity of the approach. We apply the method to data from a recent German case-control study on smoking and lung cancer risk with about 4300 lung cancer cases and a similiar number of controls. The sliding time window approach indicates that the amount of cigarettes smoked from two to 11 years before disease incidence is most predicitive of lung cancer incidence. Among different smoking profiles that result in the same lifelong cumulative number of cigarettes smoked, those with a concentration of smoked cigarettes within 20 years before interview bear substantially larger risk than others.

The adverse health effects of tobacco and tobacco-related products

Tobacco use continues to occur in epidemic proportions and with it, significant morbidity and mortality. One third of smokers will die prematurely of a smoking-related disease. This article reviews the adverse health effects of tobacco use so that clinicians can be aware of the benefits patients will reap when they stop using this lethal substance.

Trends in cigarette consumption cannot fully explain trends in British lung cancer rates

STUDY OBJECTIVES

To determine whether British lung cancer (LC) trends are adequately explained by cigarette smoking trends, and whether modelling using aggregated smoking prevalence estimates can validly replace modelling using individual smoking histories.

METHODS

Observed LC trends for 1955-1985 for both sexes and three age groups were compared with multistage model predictions using smoking history data from two surveys (HALS, AHIP). The modelling used the individual smoking data directly or aggregated prevalence estimates. It allowed for variation in age of starting and stopping smoking, amount smoked, tar levels, and environmental tobacco smoke (ETS) exposure.

RESULTS

Observed male LC rates fell faster than predicted by a model (with the first and penultimate stages assumed affected by smoking) that allowed for variation in amount smoked and in tar level (with some provision for "compensation"), and was based on aggregated smoking data from HALS. The discrepancy equated to an annual change unexplained by smoking of -2.4%, -2.8%, and -1.9% for ages 35-44, 45-54, and 55-64. The annual unexplained changes were less in women, and reversed at age 55-64; -1.7%, -0.8%, and +0.8% for the three ages. They were similar using individual smoking histories (-2.6%, -1.8%, and -1.6%; women, -0.9%, -0.5%, and +0.2%). The discrepancies were unexplained by plausible alternative multistage parameters, full allowance for tar reduction, alternative estimates of amount smoked, or ETS.

CONCLUSIONS

British LC trends cannot be fully explained by cigarette consumption trends, implying factors other than cigarette smoking contribute importantly to overall risk. Predictions using aggregated prevalence estimates provide useful information.

Is screening for chronic obstructive pulmonary disease justified?

BACKGROUND

Many experts recommend spirometry to screen for chronic obstructive pulmonary disease (COPD) in asymptomatic patients; however, evidence for this recommendation has not been systematically reviewed.

METHODS

We examined whether screening spirometry meets standard criteria for effective screening. We performed structured searches of MEDLINE, followed by a selective search of the CITATION index, to locate randomized trials of interventions for asymptomatic patients with COPD. In regard to smoking cessation, we included all controlled trials of smoking cessation programs that used spirometry. We also included all studies that assessed the ability of spirometry to predict successful smoking cessation by comparing baseline lung function in smokers who subsequently quit versus those who did not.

RESULTS

With the exception of smoking cessation, all interventions for COPD have only been proven effective in symptomatic patients. Two studies found that multifaceted smoking cessation programs that included spirometry were efficacious. There was no effect in a third study that isolated the role of spirometry. Smokers with abnormal spirometric results are less likely than other smokers to quit over the ensuing year.

CONCLUSIONS

There is no evidence that spirometry, as an isolated intervention, aids smoking cessation.

Evaluation of DNA damage in leukocytes of ex-smokers by single cell gel electrophoresis

Single cell gel electrophoresis (SCGE), or comet assay, appears to be a promising tool to estimate DNA damage at the single cell level and it provides information on the presence of damage among individual cells. A follow-up study of 90 smokers who ceased smoking was undertaken to determine the possible decrease of DNA damage in their leukocytes. Before beginning the trial, volunteers smoked on average 26.1 +/- 8.4 cigarettes/day. Comet length did not correlate with the number of cigarettes/day or with the condensate tar content. At the end of the study, 28 volunteers had abandoned the trial, 40 volunteers relapsed into smoking at different times, but with a reduced number of cigarettes/day, whereas 22 fully succeeded in smoking cessation. Throughout the 5 sampling times, a great variability of comet length at individual level was found. However, after 1 year of follow-up, comet length means were found to be significantly shorter (p < 0.0001) in those volunteers who completely quit smoking compared to those who relapsed into smoking (27.2 +/- 1.6 vs. 31.9 +/- 5.1 microns, respectively), irrespective of the amount of cigarettes previously smoked. No effect of age or sex was found. Six months later, these results were confirmed by a further study carried out on a reduced sample of volunteers. The present data strongly suggest that, in spite of the great variability observed, 1 year of smoking cessation is associated with a significant reduction of DNA damage in circulating leukocytes.

Cigarette smoking at hire as a predictor of employment outcome

We have reported that cigarette smoking at the time of hire is associated with elevated rates of accidents, injuries, absence, discipline, and firing among US postal workers. We followed this cohort of 2537 for a second year to assess whether these associations would change with time in a workplace with active smoking cessation programs. Smokers' elevated risks for accidents, injuries, and discipline decreased after the first year. Risk for involuntary turnover was slightly higher in the 2-year analysis. The elevation in the rate of absence for smokers remained comparable in both periods. Although it is possible that the decline in the relative risk of accidents, injuries, and discipline may reflect changes in smoking status, we were unable to obtain follow-up data on smoking status to test this hypothesis.

Tobacco use and its contribution to early cancer mortality with a special emphasis on cigarette smoking

This paper provides an overview of the relationship between tobacco use and early cancer mortality. It presents a retrospective examination of trends in smoking behavior and how these trends affected the national lung cancer mortality pattern during this century. Information on smoking prevalence is presented for black and white men and women for each 5-year birth cohort between 1885 and 1969. The author argues that the lung cancer mortality pattern observed in the United States since 1950 is entirely compatible with changes in smoking behavior among the various birth cohorts examined. The paper also reviews our current scientific knowledge about the etiological relationship between cigarette smoking and site-specific cancer mortality, with particular emphasis on lung cancer. Data on other forms of tobacco use and cancer mortality risks are included as are data on environmental tobacco smoke exposures and nonsmokers' lung cancer risk. Data are presented to demonstrate that cigarette use alone will be responsible for nearly one-third of the U.S. cancer deaths expected in the United States in 1995, or 168,000 premature cancer deaths. Among males, 38% of all cancer deaths are cigarette related, while among women 23% of all cancer deaths are due to cigarettes. These totals, however, include neither the cancer deaths that could reasonably be attributed to pipe, cigar, and smokeless tobacco use among males nor the estimated 3000 to 6000 environmental tobacco smoke-related lung cancer deaths that occur annually in nonsmokers. It is concluded that tobacco use, particularly the practice of cigarette smoking, is the single greatest cause of excess cancer mortality in U.S. populations.