Passive smoking and lung cancer: a cumulative meta-analysis

OBJECTIVE: To review the epidemiological evidence for the association between passive smoking and lung cancer. METHOD: Primary studies and meta-analyses examining the relationship between passive smoking and lung cancer were identified through a computerised literature search of Medline and Embase, secondary references, and experts in the field of passive smoking. Primary studies meeting the inclusion criteria were meta-analysed. RESULTS: From 1981 to the end of 1999 there have been 76 primary epidemiological studies of passive smoking and lung cancer, and 20 meta-analyses. There were 43 primary studies that met the inclusion criteria for this meta-analysis; more studies than previous assessments. The pooled relative risk (RR) for never-smoking women exposed to environmental tobacco smoke (ETS) from spouses, compared with unexposed never-smoking women was 1.29 (95% CI 1.17-1.43). Sequential cumulative meta-analysed results for each year from 1981 were calculated: since 1992 the RR has been greater than 1.25. For Western industrialised countries the RR for never-smoking women exposed to ETS compared with unexposed never-smoking women, was 1.21 (95% CI 1.10-1.33). Previously published international spousal meta-analyses have all produced statistically significant RRs greater than 1.17. CONCLUSIONS: The abundance of evidence in this paper, and the consistency of findings across domestic and workplace primary studies, dosimetric extrapolations and meta-analyses, clearly indicates that non-smokers exposed to ETS are at increased risk of lung cancer. IMPLICATIONS: The recommended public health policy is for a total ban on smoking in enclosed public places and work sites.     

Mesothelioma and lung cancer among motor vehicle mechanics: a meta-analysis

We conducted a systematic review and analysis of the epidemiological literature that examines the risk of lung cancer and mesothelioma among motor vehicle mechanics who may have been engaged in brake repair and, thus, were potentially exposed to asbestos. All relevant studies were classified into three tiers according to their quality. Tier III (lowest quality) studies were cited for completeness, but were not included in the meta-analysis. Meta relative risks (meta-RRs) were calculated for mesothelioma and lung cancer using both fixed and random effects models for Tiers I and II, separately, followed by stratified analyses based on study design or exposure characterization (garage workers versus brake workers) and, for lung cancer studies, based on adequate adjustment for smoking. The meta-analysis for Tier I (higher quality) and Tier II (lower quality) studies of mesothelioma yielded RR estimates of 0.92 (95% CI 0.55-1.56) and 0.81 (95% CI 0.52-1.28), respectively. Further stratification according to exposure characterization did not affect the results. The meta-analysis for lung cancer produced RR estimates of 1.07 (95% CI 0.88-1.31) for Tier I and 1.17 (95% CI 1.01-1.36) for Tier II. When the lung cancer analysis was limited to studies that used adequate control for smoking, the resulting RR estimate was 1.09 (95% CI 0.92-1.28). Based on these findings, we conclude that employment as a motor vehicle mechanic does not increase the risk of developing mesothelioma. Although some studies showed a small increase in risk of lung cancer among motor vehicle mechanics, the data on balance do not support a conclusion that lung cancer risk in this occupational group is related to asbestos exposure.     

Meta-analysis of silicosis and lung cancer

OBJECTIVES: This study examined the association between silicosis and lung cancer in a systematic review (and meta-analysis) of the epidemiologic literature, with special reference to the methodological quality of observational studies. METHODS: We searched Medline, Toxline, BIOSIS and Embase (1966-May 2004) for original articles published in any language and systematically reviewed the bibliographies of the retrieved articles. Observational studies (cohort and case-control studies) were selected if they reported a measure of association [standardized mortality ratio (SMR), relative risk or odds ratio] relating lung cancer to silicosis. RESULTS: Thirty-one studies (27 cohort studies, 4 case-control studies) met the inclusion criteria of the meta-analysis. Without any adjustment for smoking, the meta-analysis of the cohort studies indicated that the common SMR was 2.45 [95% confidence interval (95% CI) 1.63-3.66; homogeneity P<0.0001]. When the results of the cohorts for which mortality data were adjusted for smoking were pooled, the common SMR was 1.60 (95% CI 1.33-1.93; homogeneity P=0.52). In a "dose-response" analysis, the profusion of small and large opacities found in chest X-rays correlated with the risk of death from lung cancer. Overall, the case-control studies were more conservative in their conclusions. CONCLUSIONS: Because of biases inherent to observational studies, it is likely that the risk of lung cancer among silicosis patients is overestimated in the current literature. There is nevertheless evidence, from data restricted to never-smokers and from a "dose-response" analysis, that silicosis and lung cancer are associated.     

Meta- and pooled analysis of GSTT1 and lung cancer: a HuGE-GSEC review

Lung cancer is the most common malignancy in the Western world, and the main risk factor is tobacco smoking. Polymorphisms in metabolic genes may modulate the risk associated with environmental factors. The glutathione S-transferase theta 1 gene (GSTT1) is a particularly attractive candidate for lung cancer susceptibility because of its involvement in the metabolism of polycyclic aromatic hydrocarbons found in tobacco smoke and of other chemicals, pesticides, and industrial solvents. The frequency of the GSTT1 null genotype is lower among Caucasians (10-20%) than among Asians (50-60%). The authors present a meta- and a pooled analysis of case-control, genotype-based studies that examined the association between GSTT1 and lung cancer (34 studies, 7,629 cases and 10,087 controls for the meta-analysis; 34 studies, 7,044 cases and 10,000 controls for the pooled analysis). No association was observed between GSTT1 deletion and lung cancer for Caucasians (odds ratio (OR) = 0.99, 95% confidence interval (CI): 0.87, 1.12); for Asians, a positive association was found (OR = 1.28, 95% CI: 1.10, 1.49). In the pooled analysis, the odds ratios were not significant for either Asians (OR = 0.97, 95% CI: 0.83, 1.13) or Caucasians (OR = 1.09, 95% CI: 0.99, 1.21). No significant interaction was observed between GSTT1 and smoking on lung cancer, whereas GSTT1 appeared to modulate occupational-related lung cancer.     

孕妇被动吸烟与低出生体重关系的Meta分析

目的分析孕妇孕早期和不同孕期被动吸烟对新生儿低出生体重的影响。方法通过Meta分析方法分析孕妇被动吸烟与新生儿低出生体重之间的关系。对NCBI、OVID-MEDLINE、CNKI、VIP以及CBM数据库进行检索(截止日期为2008年4月),结果报告合并OR值及95%CI。结果共获得26篇文献,其中队列研究20篇,病例对照研究6篇。总体分析,孕妇被动吸烟的合并效应值OR=1.65(95%CI:1.39～1.97);调整合并效应值OR=1.60(95%CI:1.25～2.05);最低和最高暴露量的合并效应值分别为OR=1.53(95%CI:1.14～2.04)和OR=2.53(95%CI:1.46～4.36);孕早期暴露的合并效应值OR=1.12(95%CI:0.82～1.55),没有统计学意义。结论孕妇被动吸烟增加新生儿低出生体重的危险性;孕中晚期可能是被动吸烟效应的敏感期;被动吸烟的阈值是否存在尚不明确。     

Dose-specific meta-analysis and sensitivity analysis of the relation between alcohol consumption and lung cancer risk

Alcohol drinking increases the risk of several types of cancer, but studies of the relation between alcohol and lung cancer risk are complicated by smoking. The authors carried out meta-analyses for four study designs and conducted sensitivity analyses to assess the results. Pooled smoking-unadjusted relative risks (RRs) for brewery workers and alcoholics were 1.17 (95% confidence interval (CI): 0.99, 1.39) and 1.99 (95% CI: 1.66, 2.39), respectively, relative to population rates. For cohort and case-control studies, the authors conducted dose-specific meta-analyses for ethanol consumption of 1-499, 500-999, 1,000-1,999, and > or = 2,000 g/month, relative to nondrinking. Smoking-adjusted RRs for ascending dose groups in cohort studies were 0.98 (95% CI: 0.79, 1.21), 0.92 (95% CI: 0.81, 1.04), 1.04 (95% CI: 0.88, 1.22), and 1.53 (95% CI: 1.04, 2.25), respectively. Smoking-adjusted odds ratios for ascending groups in case-control studies were 0.63 (95% CI: 0.51, 0.78), 1.30 (95% CI: 0.98, 1.70), 1.13 (95% CI: 0.46, 2.75), and 1.86 (95% CI: 1.39, 2.49), respectively. Elevated odds ratios were seen for hospital-based case-control studies but not for population-based case-control studies. Sensitivity analyses indicated that smoking explained the elevated RRs in studies of alcoholics and that strong misclassification of smoking status could produce an elevated smoking-adjusted RR in cohort and case-control studies. Overall, evidence for a smoking-adjusted association between alcohol and lung cancer risk is limited to very high consumption groups in cohort and hospital-based case-control studies. At lower levels, any associations observed appear to be explained by confounding.     

Active and passive smoking and risk of colds in women

PURPOSE: To evaluate the association between active and passive smoking and frequency of colds in women. METHODS: Data on cigarette smoking and frequency and duration of colds were analyzed in the Women's Health Study (WHS), a randomized, double-blind, placebo-controlled trial of low-dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer among 39,876 female health professionals. RESULTS: After adjustment for age, body-mass index, prevalence of asthma and chronic lung diseases, alcohol intake, physical activity, and multivitamin use, current heavy smokers had no appreciable increase in the frequency of colds (relative risk (RR) for >or= 3 versus no colds in the past year, 1.05; 95% confidence interval (CI), 0.80-1.39), but a significantly increased risk of prolonged colds (RR for colds of > 7 vs. 1-3 days, 2.53; 95% CI, 1.95-3.29). There was no difference in the number of days confined to home. Nonsmoking women passively exposed to cigarette smoke had a slightly increased risk of both more frequent colds (RR, 1.33; 95% CI, 1.18-1.51) and more prolonged colds during the previous year (RR, 1.12; 95% CI, 0.99-1.27). CONCLUSIONS: Women who are currently heavy smokers are at increased risk of having colds with longer duration compared with nonsmokers. Nonsmoking women passively exposed to cigarette smoking are at slightly increased risk of having more frequent and longer colds than nonsmoking women not exposed to passive smoke.     

Fish Consumption and Lung Cancer Risk: Systematic Review and Meta-Analysis

There is evidence pointing to a possible role of diet on cancer etiology. Prior studies evaluating the relationship between fish consumption and lung cancer risk reported inconclusive results. The aim of this study was to achieve a comprehensive assessment of the relationship between fish consumption and lung cancer risk through systematic review and meta-analysis. Case control and cohort studies up to September 1, 2012 about fish consumption and lung cancer risk were confirmed by an online search. Separate relative risk (RR) or odds ratio (OR) estimates with 95% confidence interval (CI) of the relationship between lung cancer risk and fish consumption level from the included articles were combined by Stata11.0 software. Publication bias was evaluated by Egger's linear regression test and funnel plot. Twenty articles (17 case-control and 3 cohort studies) comprising 8799 cases of lung cancer and 17,072 noncases were included in the final analysis. The pooled results from all studies indicated that high fish consumption was significantly associated with a decreased risk of lung cancer (pooled RR: 0.79; 95% CI: 0.69–0.92). There was heterogeneity among the studies (I² = 73%, P < 0.05). Pooled RR in case control and cohort studies were 0.76 (95% CI: 0.63–0.91) and 0.95 (95% CI: 0.73–1.24), respectively. Omission of any single study had little effect on the combined risk estimates. This article had no publication bias. This study identifies a significant association between fish consumption and lung cancer, confirming a protective role of fish in lung cancer. More well-designed prospective studies are required to further verify the effect of fish consumption on lung cancer.     

Alcohol consumption and the risk of endometrial cancer: a meta-analysis

Epidemiologic findings are inconsistent concerning the association of endometrial cancer risk with alcohol consumption. Therefore, we conduct a meta-analysis of studies that assessed the association of alcohol consumption and the risk of endometrial cancer. A systematic literature search up to April 2010 was performed in MEDLINE and EMBASE, and study-specific risk estimates were pooled using a random-effects model. In the present study, six prospective and 14 case-control studies were included. Alcohol intake was not significantly associated with the risk of endometrial cancer among prospective studies (relative risk (RR): 1.04; 95% confidence interval (CI): 0.91-1.18) or among case-control studies (odds ratio (OR): 0.89; 95% CI: 0.76-1.05). However evidence from the results of our stratified analyses revealed that increased risk of endometrial cancer was associated with liquor consumption (RR: 1.22; 95% CI: 1.03-1.45) but null association with wine and beer consumption. In conclusion, alcohol consumption is not associated with the risk of endometrial cancer. Future studies should also examine whether the relation varies according to different type of alcoholic beverages.     

Passive smoking and lung cancer in nonsmoking women.

OBJECTIVES. The causes of lung cancer among nonsmokers are not clearly understood. To further evaluate the relation between passive smoke exposure and lung cancer in nonsmoking women, we conducted a population-based, case-control study. METHODS. Case patients (n = 618), identified through the Missouri Cancer Registry for the period 1986 through 1991, included 432 lifetime nonsmokers and 186 ex-smokers who had stopped at least 15 years before diagnosis or who had smoked for less than 1 pack-year. Control subjects (n = 1402) were selected from driver's license and Medicare files. RESULTS. No increased risk of lung cancer was associated with childhood passive smoke exposure. Adulthood analyses showed an increased lung cancer risk for lifetime nonsmokers with exposure of more than 40 pack-years from all household members (odds ratio [OR] = 1.3; 95% confidence interval [CI] = 1.0, 1.8) or from spouses only (OR = 1.3; 95% CI = 1.0, 1.7). When the time-weighted product of pack-years and average hours exposed per day was considered, a 30% excess risk was shown at the highest quartile of exposure among lifetime nonsmokers. CONCLUSIONS. Ours and other recent studies suggest a small but consistent increased risk of lung cancer from passive smoking. Comprehensive actions to limit smoking in public places and worksites are well-advised.     

Meta- and pooled analyses of the methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and gastric cancer risk: a huge-GSEC review

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in the metabolism of folate, whose role in gastric carcinogenesis is controversial. The authors performed a meta-analysis and individual data pooled analysis of case-control studies that examined the association between C677T and A1298C polymorphisms (the former being associated with low folate serum levels) and gastric cancer (meta-analyses: 16 studies, 2,727 cases and 4,640 controls for C677T and seven studies, 1,223 cases and 2,015 controls for A1298C; pooled analyses: nine studies, 1,540 cases and 2,577 controls for C677T and five studies, 1,146 cases and 1,549 controls for A1298C). An increased risk was found for MTHFR 677 TT in the meta-analysis (odds ratio (OR) = 1.52, 95% confidence interval (CI): 1.31, 1.77) and pooled analysis (OR = 1.49, 95% CI: 1.14, 1.95). No association resulted for MTHFR 1298 CC (meta-OR = 0.94, 95% CI: 0.65, 1.35; pooled OR = 0.90, 95% CI: 0.69, 1.34). Results from the pooled analysis of four studies on C677T stratified according to folate levels showed an increased risk for individuals with low (OR = 2.05, 95% CI: 1.13, 3.72) versus high (OR = 0.95, 95% CI: 0.54, 1.67) folate levels. Overall, these findings support the hypothesis that folate plays a role in gastric carcinogenesis.     

Diesel exhaust exposure and lung cancer: adjustment for the effect of smoking in a retrospective cohort study

BACKGROUND: The extent that cigarette smoking may confound the relationship between diesel exhaust exposure and lung cancer was assessed in a retrospective cohort study of 55,395 U.S. railroad workers followed from 1959 to 1976. METHODS: The relative risk (RR) of lung cancer due to diesel exhaust was indirectly adjusted using job-specific smoking data from a case-control study of railroad workers who died between 1981-1982 and from a survey of 514 living workers from an active railroad in 1982. Adjustment factors were developed based on the distribution of job-specific smoking rates. RESULTS: The unadjusted RR for lung cancer was 1.58 (95% CI = 1.14-2. 20) for workers aged 40-44 in 1959, who experienced the longest possible duration of exposure, and the smoking adjusted RR was 1.44 (1.01-2.05). CONCLUSIONS: After considering differences in smoking rates between workers exposed and unexposed to diesel exhaust in a relatively large blue-collar cohort, there were still elevated risks of lung cancer in workers in jobs with diesel exhaust exposure.     

老年人接种23价肺炎球菌多糖疫苗保护效果的Meta分析

目的 评价60岁以上老年人接种23价肺炎球菌多糖疫苗(PPV23)对侵袭性肺炎球菌疾病(IPD)和肺炎球菌肺炎(PP)的保护效果.方法 电子检索National Center for Biotechnology Information、Cochrane Library、中国生物医学文献数据库、中国期刊全文数据库和万方全文数据库等数据库,将60岁以上老年人接种PPV23流行病学保护效果的随机对照试验、队列研究、病例对照研究纳入研究.合并各项研究中关于接种组和对照组间发生IPD、PP的相对危险度(RR)或比值比(OR).在合并RR或OR有统计学意义的情况下,计算疫苗效力.使用RevMan 5.3软件进行统计分析.结果 共纳入4篇随机对照研究、5篇队列研究和8篇病例对照研究.随机对照研究合并后显示接种PPV23后对IPD和PP的疫苗效力分别是73％(95％CI:10％～92％),64％ (95％ CI:35％ ～80％);队列研究合并后显示对IPD和PP的疫苗效力分别为45％ (95％CI:15％～65％),48％ (95％CI:25％～63％);病例对照研究合并显示对IPD和PP的疫苗效力分别是59％ (95％ CI:35％～74％),45％(95％CI:27％～59％).结论 60岁以上老年人接种PPV23后对IPD和PP均有良好的保护效果,而且由于PPV23覆盖肺炎球菌血清型别较广,可以有效减少IPD、PP发病,值得在60岁以上老年人中推广使用.     

Dairy Product Consumption and Risk of Non-Hodgkin Lymphoma: A Meta-Analysis

Many epidemiologic studies have explored the association between dairy product consumption and the risk of non-Hodgkin lymphoma (NHL), but the results remain controversial. A literature search was performed in PubMed, Web of Science and Embase for relevant articles published up to October 2015. Pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated with a random-effects model. The dose-response relationship was assessed by restricted cubic spline. A total of 16 articles were eligible for this meta-analysis. The pooled RRs (95% CIs) of NHL for the highest vs. lowest category of the consumption of total dairy product, milk, butter, cheese, ice cream and yogurt were 1.20 (1.02, 1.42), 1.41 (1.08, 1.84), 1.31 (1.04, 1.65), 1.14 (0.96, 1.34), 1.57 (1.11, 2.20) and 0.78 (0.54, 1.12), respectively. In subgroup analyses, the positive association between total dairy product consumption and the risk of NHL was found among case-control studies (RR = 1.41, 95% CI: 1.17–1.70) but not among cohort studies (RR = 1.02, 95% CI: 0.88–1.17). The pooled RRs (95% CIs) of NHL were 1.21 (1.01, 1.46) for milk consumption in studies conducted in North America, and 1.24 (1.09, 1.40) for cheese consumption in studies that adopted validated food frequency questionnaires. In further analysis of NHL subtypes, we found statistically significant associations between the consumption of total dairy product (RR = 1.73, 95% CI: 1.22–2.45) and milk (RR = 1.49, 95% CI: 1.08–2.06) and the risk of diffuse large B-cell lymphoma. The dose-response analysis suggested that the risk of NHL increased by 5% (1.05 (1.00–1.10)) and 6% (1.06 (0.99–1.13)) for each 200 g/day increment of total dairy product and milk consumption, respectively. This meta-analysis suggested that dairy product consumption, but not yogurt, may increase the risk of NHL. More prospective cohort studies that investigate specific types of dairy product consumption are needed to confirm this conclusion.     

Active and passive smoking and risk of breast cancer by age 50 years among German women

Recent studies suggest that both active and passive smokers have an increased risk of breast cancer compared with women who have never been either actively or passively exposed. Data on lifetime active and passive smoking were collected in 1999-2000 from 468 predominantly premenopausal breast cancer patients diagnosed by age 50 years and 1,093 controls who had previously participated in a German case-control study conducted in 1992-1995. Compared with never active/passive smokers, former smokers and current smokers had odds ratios of 1.2 (95% confidence interval (CI): 0.8, 1.7) and 1.5 (95% CI: 1.0, 2.2), respectively, and ever active smokers had an odds ratio of 1.3 (95% CI: 0.9, 1.9). The risk increased with duration of smoking and decreased after cessation of smoking. Among never active smokers, ever passive smoking was associated with an odds ratio of 1.6 (95% CI: 1.1, 2.4). Exposure to environmental tobacco smoke during childhood or before the first pregnancy did not appear to increase breast cancer risk. At greatest risk were women who had a high level of exposure to both passive and active smoking (odds ratio = 1.8, 95% CI: 1.2, 2.7). This study strengthens the hypothesis of a causal relation between active and passive smoke exposures and breast cancer risk.     

Vitamin D can safely reduce asthma exacerbations among corticosteroid-using children and adults with asthma: a systematic review and meta-analysis of randomized controlled trials

Previous studies have failed to draw a consistent conclusion over the effect of vitamin D administration on asthma. We hypothesized that vitamin D supplementation could improve the clinical efficacy of corticosteroids in patients with asthma as measured by exacerbations, Asthma Control Test (ACT) score, and lung function in order to maintain asthma control. We searched Web of Science, PubMed, the Cochrane Library, and ScienceDirect up through January 20, 2021 for randomized controlled trials analyzing the effect of vitamin D supplementation on asthma exacerbation. Studies were limited to patients with moderate to severe asthma who were treated with corticosteroids. We identified 12 studies involving 1,543 participants in this meta-analysis. Vitamin D supplementation significantly reduced the risk of asthma exacerbation (pooled risk ratio (RR) 0.70, 95% confidence interval (CI), 0.59, 0.83; P < .05). The pooled RR of the ACT score was 0.04 (95% CI, −0.19, 0.27; P > .05). The pooled standardized mean difference in vitamin D levels was 1.07 (95% CI, 0.77, 1.38; P < .05), and in the percentage of forced expiratory volume in one second was −0.02 (95% CI, −0.13, 0.09; P > .05). The pooled RR of adverse events was 1.06 (95% CI, 0.89, 1.25; P > .05). We performed subgroup analysis and meta-regression of serum vitamin D levels but found no source of heterogeneity. Vitamin D supplementation safely reduced the rate of asthma exacerbation but did not improve ACT score or lung function among patients with asthma treated with corticosteroids.     

Smoking imputation and lung cancer in railroad workers exposed to diesel exhaust

BACKGROUND: An association between diesel exhaust exposure and lung cancer mortality in a large retrospective cohort study of US railroad workers has previously been reported. However, specific information regarding cigarette smoking was unavailable. METHODS: Birth cohort, age, job, and cause of death specific smoking histories from a companion case-control study were used to impute smoking behavior for 39,388 railroad workers who died 1959-1996. Mortality analyses incorporated the effect of smoking on lung cancer risk. RESULTS: The smoking adjusted relative risk of lung cancer in railroad workers exposed to diesel exhaust compared to unexposed workers was 1.22 (95% CI = 1.12-1.32), and unadjusted for smoking the relative risk was 1.35 (95% CI = 1.24-1.46). CONCLUSIONS: These analyses illustrate the use of imputation in record-based occupational health studies to assess potential confounding due to smoking. In this cohort, small differences in smoking behavior between diesel exposed and unexposed workers did not explain the elevated lung cancer risk.     

Involuntary smoking and lung cancer

Involuntary smoking contains human carcinogens. Exposure prevalence among adults is on the order of 40%. A meta-analysis of epidemiologic studies on lung cancer and exposure to involuntary smoking from the spouse included 51 studies. The overall relative risk (RR), based on 7369 cases of lung cancer, was 1.25 [95% confidence interval (95% CI) 1.15-1.37]. No evidence existed of an RR difference between the two genders, and study design had no influence on the results. The summary RR was lower for adenocarcinoma than for other histological types. In the largest studies cumulative exposure suggested a dose-response relationship with a unit risk of similar magnitude. The summary RR was 1.17 (95% CI 1.04-1.32) for workplace exposure. Several sources of bias may lead to both overestimation and underestimation of true association, and the most plausible interpretation favors a causal association. Even if excess risk from exposure to involuntary smoking is small, its large prevalence makes it an important environmental carcinogen.     

Citrus fruit intake and bladder cancer risk: a meta-analysis of observational studies

Epidemiological studies have investigated the association between citrus fruit and bladder cancer risk; however, the results are inconsistent. To assess these issues, we conducted a meta-analysis of currently available studies. We identified relevant articles by searching the MEDLINE and EMBASE databases. We calculated the summary relative risk (RR) with 95% confidence interval (95% CI) using a random effect model. We included eight case–control studies and six cohort studies in the meta-analysis. There was a significant inverse association between citrus fruit intake and bladder cancer risk in all pooled studies (RR: 0.85; 95% CI, 0.76–0.94) and case–control studies (RR: 0.77; 95% CI, 0.64–0.92), but not in the cohort studies (RR: 0.96; 95% CI, 0.87–1.07). Our results suggest that citrus fruit intake is related to decreased bladder cancer risk. Subsequent well-designed, large prospective studies are needed to obtain better understanding of this relationship.     

Active and passive smoking in breast cancer: prospective results from the Nurses' Health Study

BACKGROUND: The role of active and passive smoking in breast cancer remains controversial. METHODS: Using data collected in the prospective Nurses' Health Study, we examined the influence of active and passive smoking on the incidence of invasive breast cancer. The analysis was based on women responding to the 1982 questionnaire, which included questions on passive smoking exposure. Information on active smoking was collected in biennial questionnaires. A total of 78,206 women were followed prospectively from 1982 until June 1996. RESULTS: Of these women, 3,140 reported a diagnosis of invasive breast cancer during follow-up. Compared with never active smoking, relative risks (RR) of breast cancer were 1.04 (95% CI = 0.94-1.15) for current active smoking and 1.09 (95% CI = 1.00-1.18) for past active smoking. The RR for regular passive exposure at work and at home was 0.90 (95% CI = 0.67-1.22). For active smoking, a modest increase in risk was confined to women who began smoking before the age of 17 (RR = 1.19; 95% CI = 1.03-1.37). CONCLUSION: Results suggest that passive smoking is unrelated to breast cancer. However, results for active smoking are compatible with a small increase in risk when smoking is initiated at young ages.