Reproductive factors, exogenous hormone use and risk of hepatocellular carcinoma among US women: results from the Liver Cancer Pooling Project.

BACKGROUND: Hepatocellular carcinoma (HCC) occurs less commonly among women than men in almost all regions of the world. The disparity in risk is particularly notable prior to menopause suggesting that hormonal exposures during reproductive life may be protective. Exogenous oestrogenic exposures such as oral contraceptives (OCs), however, have been reported to increase risk, suggesting that estrogens may be hepatocarcinogenic. To examine the effects of reproductive factors and exogenous hormones on risk, we conducted a prospective analysis among a large group of US women. METHODS: In the Liver Cancer Pooling Project, a consortium of US-based cohort studies, data from 799,500 women in 11 cohorts were pooled and harmonised. Cox proportional hazards regression models were used to generate hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations of reproductive factors and exogenous hormones with HCC (n=248). RESULTS: Bilateral oophorectomy was associated with a significantly increased risk of HCC (HR=2.67, 95% CI=1.22-5.85), which did not appear to be related to a shorter duration of exposure to endogenous hormones or to menopausal hormone therapy use. There was no association between OC use and HCC (HR=1.12, 95% CI=0.82-1.55). Nor were there associations with parity, age at first birth, age at natural menopause, or duration of fertility. CONCLUSIONS: The current study suggests that bilateral oophorectomy increases the risk of HCC but the explanation for the association is unclear. There was no association between OC use and HCC risk. Examination of endogenous hormone levels in relation to HCC may help to clarify the findings of the current study.

Investing in prospective cohorts for etiologic study of occupational exposures.

Prospective cohorts have played a major role in understanding the contribution of diet, physical activity, medical conditions, and genes to the development of many diseases, but have not been widely used for occupational exposures. Studies in agriculture are an exception. We draw upon our experience using this design to study agricultural workers to identify conditions that might foster use of prospective cohorts to study other occupational settings. Prospective cohort studies are perceived by many as the strongest epidemiologic design. It allows updating of information on exposure and other factors, collection of biologic samples before disease diagnosis for biomarker studies, assessment of effect modification by genes, lifestyle, and other occupational exposures, and evaluation of a wide range of health outcomes. Increased use of prospective cohorts would be beneficial in identifying hazardous exposures in the workplace. Occupational epidemiologists should seek opportunities to initiate prospective cohorts to investigate high priority, occupational exposures.

Pesticide use and adult-onset asthma among male farmers in the Agricultural Health Study.

Although specific pesticides have been associated with wheeze in farmers, little is known about pesticides and asthma. Data from 19,704 male farmers in the Agricultural Health Study were used to evaluate lifetime use of 48 pesticides and prevalent adult-onset asthma, defined as doctor-diagnosed asthma after the age of 20 yrs. Asthma cases were categorised as allergic (n = 127) and nonallergic (n = 314) based on their history of eczema or hay fever. Polytomous logistic regression, controlling for age, state, smoking and body mass, was used to assess pesticide associations. High pesticide exposure events were associated with a doubling of both allergic and nonallergic asthma. For ever-use, 12 individual pesticides were associated with allergic asthma and four with nonallergic asthma. For allergic asthma, coumaphos (OR 2.34; 95% CI 1.49-3.70), heptachlor (OR 2.01; 95% CI 1.30-3.11), parathion (OR 2.05; 95% CI 1.21-3.46), 80/20 mix (carbon tetrachloride/carbon disulfide) (OR 2.15; 95% CI 1.23-3.76) and ethylene dibromide (OR 2.07; 95% CI 1.02-4.20) all showed ORs of >2.0 and significant exposure-response trends. For nonallergic asthma, DDT (dichlorodiphenyltrichloroethane) showed the strongest association (OR 1.41; 95% CI 1.09-1.84), but with little evidence of increasing asthma with increasing use. Current animal handling and farm activities did not confound these results. There was little evidence that allergy alone was driving these associations. In conclusion, pesticides may be an overlooked contributor to asthma risk among farmers.

Rhinitis associated with pesticide exposure among commercial pesticide applicators in the Agricultural Health Study.

OBJECTIVES: Rhinitis is common, but the risk factors are not well described. To investigate the association between current rhinitis and pesticide use, we used data from 2245 Iowa commercial pesticide applicators in the Agricultural Health Study. METHODS: Using logistic regression models adjusted for age, education and growing up on a farm, we evaluated the association between current rhinitis and 34 pesticides used in the past year. RESULTS: 74% of commercial pesticide applicators reported at least one episode of rhinitis in the past year (current rhinitis). Five pesticides used in the past year were significantly positively associated with current rhinitis: the herbicides 2,4-D, glyphosate and petroleum oil, the insecticide diazinon and the fungicide benomyl. The association for 2,4-D and glyphosate was limited to individuals who used both in the past year (OR 1.42, 95% CI 1.14 to 1.77). Both petroleum oil and diazinon showed consistent evidence of an association with rhinitis, based on both current use and exposure-response models. We saw no evidence of confounding by common agricultural rhinitis triggers such as handling grain or hay. CONCLUSIONS: Exposure to pesticides may increase the risk of rhinitis.

Incident diabetes and pesticide exposure among licensed pesticide applicators: Agricultural Health Study, 1993-2003.

Exposure to certain environmental toxicants may be associated with increased risk of developing diabetes. The authors' aim was to investigate the relation between lifetime exposure to specific agricultural pesticides and diabetes incidence among pesticide applicators. The study included 33,457 licensed applicators, predominantly non-Hispanic White males, enrolled in the Agricultural Health Study. Incident diabetes was self-reported in a 5-year follow-up interview (1999-2003), giving 1,176 diabetics and 30,611 nondiabetics for analysis. Lifetime exposure to pesticides and covariate information were reported by participants at enrollment (1993-1997). Using logistic regression, the authors considered two primary measures of pesticide exposure: ever use and cumulative lifetime days of use. They found seven specific pesticides (aldrin, chlordane, heptachlor, dichlorvos, trichlorfon, alachlor, and cyanazine) for which the odds of diabetes incidence increased with both ever use and cumulative days of use. Applicators who had used the organochlorine insecticides aldrin, chlordane, and heptachlor more than 100 lifetime days had 51%, 63%, and 94% increased odds of diabetes, respectively. The observed association of organochlorine and organophosphate insecticides with diabetes is consistent with results from previous human and animal studies. Long-term exposure from handling certain pesticides, in particular, organochlorine and organophosphate insecticides, may be associated with increased risk of diabetes.

Neurologic symptoms in licensed pesticide applicators in the Agricultural Health Study.

Exposure to high levels of many pesticides has both acute and long-term neurologic consequences, but little is known about the neurotoxicity of chronic exposure to moderate pesticide levels. We analysed cross-sectional data from 18 782 Caucasian, male, licensed pesticide applicators, enrolled in the Agricultural Health Study from 1993 to 1997. Applicators provided information on lifetime pesticide use, and 23 neurologic symptoms typically associated with pesticide intoxication. Increased risk of experiencing >/=10 symptoms during the year before enrollment was associated with cumulative pesticide use, personally mixing or applying pesticides, pesticide-related medical care, diagnosed pesticide poisoning, and events involving high personal pesticide exposure. Greatest risk was associated with use of organophosphate and organochlorine insecticides. Results were similar after stratification by pesticide use during the year before enrollment, or exclusion of applicators with a history of pesticide poisoning, or high-exposure events. Use of pesticide application methods likely to involve high personal exposure was associated with greater risk. Groups of symptoms reflecting several neurologic domains, including affect, cognition, autonomic and motor function, and vision, were also associated with pesticide exposure. These results suggest that neurologic symptoms are associated with cumulative exposure to moderate levels of organophosphate and organochlorine insecticides, regardless of recent exposure or history of poisoning.

Cancer mortality in the U.S. flour industry.

The mortality experience among 22,938 white males who were enrolled in the life insurance program of the American Federation of Grain Millers was assessed for the period 1955 through 1985 in a cohort mortality analysis and in a nested case-control analysis. Significantly fewer deaths were observed among this group than expected for all causes of death combined [standardized mortality ratio (SMR) = 89] compared with the number of deaths observed among the general population of U.S. white males of the same age. Excess risks for developing non-Hodgkin's lymphoma (NHL) (SMR = 149), leukemia (SMR = 136), and pancreatic cancer (SMR = 133) were restricted to workers employed in flour mills, where pesticides are used more frequently than in other segments of the industry. In the nested case-control analysis, excess risks for developing these cancers were also observed in these workers, but the relative risk for developing NHL [odds ratio (OR) = 4.2] was approximately twice that for developing pancreatic cancer (OR = 2.2) and that for developing leukemia (OR = 1.8). Within the flour mills, the workers who had ever worked in the maintenance department (OR = 8.1) or in the elevator department (OR = 2.8) were at particularly elevated risk of developing NHL, suggesting that exposures in these departments should receive further attention.

Saturated fat intake and lung cancer risk among nonsmoking women in Missouri.

BACKGROUND: Although the vast majority of lung cancer cases in women are caused by smoking, 9%-20% of cases occur in nonsmokers. Previous epidemiologic research on the relationship between lung cancer and diet has shown that fruit and vegetable consumption may confer a protective effect against lung cancer, while a diet rich in cholesterol and fat may increase risk. PURPOSE: The purpose of this case-control study was to examine the effects of a broad range of dietary factors on the risk of lung cancer in a population of nonsmoking white women 30-84 years of age. METHODS: A telephone-administered questionnaire was used to determine and/or verify eligibility with regard to age, gender, race, and smoking status. In a second interview at the participant's home, a widely used food frequency questionnaire was filled out, and logistic regression was subsequently used to analyze the responses. We obtained dietary information on 429 case subjects who had a diagnosis of lung cancer reported to the Missouri Cancer Registry between June 1, 1986, and June 1, 1991, and 1021 control subjects. If a case subject had died or was too ill to be interviewed, next-of-kin familiar with the woman's diet were interviewed instead. Of the 429 women with lung cancer, 211 (49%) had lung adenocarcinoma. RESULTS: A strongly increasing trend in lung cancer risk was observed with increased saturated fat consumption among these non-smoking women; the relative risk was more than sixfold greater for the highest quintile of consumption than for the lowest quintile. The effect of saturated fat was more pronounced for adenocarcinoma than for other cell types. Weekly servings of beans and peas were significantly related to decreased lung cancer risk, while citrus fruit and juice showed a twofold increase in risk; this trend was also significant. CONCLUSION: By focusing on non-smoking women with lung cancer, including a large number with adenocarcinoma, we observed a clear association with saturated fat consumption that may have been masked in earlier studies of lung cancer involving a high percentage of smokers.

Proportionate mortality study of workers in the grain industry.

The proportionate mortality experience and proportionate cancer mortality experience were examined for 1,114 white male members of the American Federation of Grain Millers' life insurance plan. Mortality was significantly elevated for accidents and cancers of the lymphatic and hematopoietic systems, particularly from lymphosarcoma and reticulum cell sarcoma, other neoplasms of lymphoid tissue (i.e., giant follicular lymphoma and other primary malignant neoplasms of lymphoid tissue), and multiple myeloma. No increased mortality was seen for cancer of the respiratory tract, and nonmalignant diseases of the digestive tract were significantly lower than expected. Employees of grain mills showed higher mortality ratios of lymphatic and hematopoietic cancers as compared to other grain industry categories. A preliminary survey of pesticide usage suggested that grain mills were generally associated with greater use of pesticides than other industrial categories with considerable variation among the many facilities encompassed in this study.

Residential radon exposure and lung cancer among nonsmoking women.

BACKGROUND: Radon at sufficiently high concentrations is known to cause lung cancer among underground miners and in experimental laboratory animals. PURPOSE: Our aim was to determine whether indoor levels of radon are associated with a detectable increase in lung cancer. Nonsmoking women were selected because they offer the best opportunity to detect radon-related risk while minimizing the potentially confounding influences of cigarette smoking and occupation. METHODS: A population-based, case-control study of incident lung cancer was conducted in Missouri. A total of 538 non-smoking white women diagnosed with lung cancer between 1986 and 1992 and 1183 age-matched control subjects were identified from the Missouri Cancer Registry and from driver's license and Medicare listings, respectively. Information on lung cancer risk factors was obtained by telephone interview. Year-long radon measurements were sought in every dwelling occupied for the previous 5-30 years. RESULTS: Radon measurements covered 78% of the relevant residential period, and women reported being indoors for 84% of this time. The time-weighted average radon concentrations were exactly the same for case subjects and control subjects (1.82 pCi/L of air [pCi L-1]). Radon levels greater than 4 pCi L-1 were experienced by 6.5% of the case subjects and 6.8% of the control subjects. For all data combined, there was little evidence for a trend of lung cancer with increasing radon concentrations (two-tailed trend test, P = .99 continuous data analysis; P = .19 categorical data analysis). A positive dose-response trend was suggested for the adenocarcinoma cell type and among directly interviewed women (two-tailed trend test; P = .31 continuous data analysis; P = .04 categorical data analysis), but not for other histologies or among those who had surrogate interviews. CONCLUSIONS: The possibility of detecting a risk from indoor radon in this study was maximized by (a) including a large number of nonsmoking women with high indoor occupancy, (b) conducting a large number of radon measurements near the time of the diagnosis of cancer, and (c) controlling for known causes of lung cancer. However, an association between lung cancer and the exposure to domestic levels of radon was not convincingly demonstrated. IMPLICATIONS: The magnitude of the lung cancer risk from radon levels commonly found in U.S. dwellings appears low.

Environmental tobacco smoke, genetic susceptibility, and risk of lung cancer in never-smoking women.

BACKGROUND: Exposure to environmental tobacco smoke (ETS) is considered to be a major lung cancer risk factor for never smokers. We investigated the hypothesis that never-smoking women who are exposed to ETS and develop lung cancer are a genetically susceptible population. METHODS: Archival tumor tissues were analyzed from 106 never-smoking women enrolled in a case-control study of ETS (and other personal and environmental factors) and lung cancer risk. We analyzed germline polymorphisms in genes that have been associated with cancer susceptibility and whose products activate (cytochrome P450 1A1 [CYP1A1]) and detoxify (glutathione S-transferases M1 [GSTM1] and T1 [GSTT1]) chemical carcinogens found in tobacco smoke. RESULTS: When compared with never smokers who had no ETS exposure and developed lung cancer (n = 55), never smokers with exposure to ETS who developed lung cancer (n = 51) were more likely to be deficient in GSTM1 activity (i.e., were GSTM1 null) because of a genetic polymorphism in the GSTM1 gene (odds ratio = 2.6; 95% confidence interval = 1.1-6.1). A statistically significant rising trend in risk occurred with increasing ETS exposure (two-sided P =. 02), reaching a more than sixfold excess risk in those exposed to 55 pack-years of ETS (ETS pack-year = ETS produced by an active smoker, within a confined space such as a room, who smokes one pack of cigarettes a day for a year). No evidence was found of associations between GSTT1 deficiency or the CYP1A1 valine variant and lung cancer risk due to ETS exposure. CONCLUSIONS: A common genetic polymorphism divides the population of never smokers into two groups of approximately equal size, one (homozygous carriers of the GSTM1 null allele) that has a statistically significant greater risk of lung cancer from ETS than the other (heterozygous or homozygous carriers of the wild-type GSTM1 allele).

Dietary heterocyclic amines and the risk of lung cancer among Missouri women.

Heterocyclic amines (HCAs) such as 2-amino-3,8-dimethylimidazo[4,5f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx,), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) are found in meats cooked at high temperatures. In rodents, MeIQx induces lung tumors. The purpose of this study was to investigate lung cancer risk posed by different HCAs in the diet. A population-based case-control study of 593 cases and 623 frequency-matched controls including both nonsmoking and smoking women was conducted in Missouri. An administered food frequency questionnaire with detailed questions on meat consumption, degrees of internal doneness, surface browning/charring, and cooking technique was linked to a database that provided exposure estimates of three HCAs. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression. When comparing the 90th and 10th percentiles, significant excess risks were observed for MeIQx (OR, 1.5; CI, 1.1-2.0), but not for DiMeIQx (OR, 1.2; CI, 0.9-1.6) or PhIP (OR, 0.9; CI, 0.8-1.1). MeIQx consumption was associated with increased risk of lung cancer for nonsmokers (OR, 3.6; CI, 1.3-10.3) and light/moderate smokers (OR, 2.1; CI, 1.3-3.3), but not for heavy smokers (OR, 1.0; CI, 0.7-1.5). There was elevated risk with MeIQx intake for subjects with squamous cell carcinomas (OR, 1.9; CI, 1.2-3.1) and "other histological cell types" (OR, 1.6; CI, 1.1-2.5), but not for subjects with small cell carcinomas and adenocarcinomas. Neither DiMeIQx nor PhIP showed an association with smoking categories or lung cancer histology. In conclusion, MeIQx may be associated with lung cancer risk, but DiMeIQx and PhIP are probably not associated with lung cancer risk.

p53 and K-ras mutations in lung cancers from former and never-smoking women.

Somatic p53 mutations are common in lung cancer. Active cigarette smoking is positively correlated with the total frequency of p53 mutations and G:C to T:A transversions on the nontranscribed (DNA coding) strand. Mutational hotspots within the p53 gene, e.g., codon 157, have been identified for tobacco-related lung cancer, whereas these same mutations are found rarely in other cancers. Such data implicate specific p53 mutations as molecular markers of smoking. Because limited data exist concerning the p53 mutation frequency and spectra in ex-smokers and nonsmokers, we have analyzed p53 and K-ras mutations in 126 lung cancers from a population-based case-control study of nonsmoking (n = 117) or ex-smoking (n = 9) women from Missouri with quantitative assessments of exposure to environmental tobacco smoke. Mutations in the p53 gene were found in lung cancers from lifetime nonsmokers (19%) and ex-smokers (67%; odds ratio, 9.08; 95% confidence interval, 2.06-39.98). All deletions were found in tumors from patients who were either ex-smokers or nonsmokers exposed to passive smoking. The G:C to A:T transitions (11 of 28; 39%) were the most frequent p53 mutations found and clustered in tumors from lifetime nonsmokers without passive smoke exposure. The incidence of K-ras codon 12 or 13 mutations was 11% (14 of 115 analyzed) with no difference between long-term ex-smokers and nonsmokers. These and other results indicate that p53 mutations occur more commonly in smokers and ex-smokers than in never-smokers. Such comparisons provide additional evidence of genetic damage caused by tobacco smoke during lung carcinogenesis.

Intercomparison of retrospective radon detectors.

We performed both a laboratory and a field intercomparison of two novel glass-based retrospective radon detectors previously used in major radon case-control studies performed in Missouri and Iowa. The new detectors estimate retrospective residential radon exposure from the accumulation of a long-lived radon decay product, (210)Pb, in glass. The detectors use track registration material in direct contact with glass surfaces to measure the alpha-emission of a (210)Pb-decay product, (210)Po. The detector's track density generation rate (tracks per square centimeter per hour) is proportional to the surface alpha-activity. In the absence of other strong sources of alpha-emission in the glass, the implanted surface alpha-activity should be proportional to the accumulated (210)Po, and hence to the cumulative radon gas exposure. The goals of the intercomparison were to a) perform collocated measurements using two different glass-based retrospective radon detectors in a controlled laboratory environment to compare their relative response to implanted polonium in the absence of environmental variation, b) perform collocated measurements using two different retrospective radon progeny detectors in a variety of residential settings to compare their detection of glass-implanted polonium activities, and c) examine the correlation between track density rates and contemporary radon gas concentrations. The laboratory results suggested that the materials and methods used by the studies produced similar track densities in detectors exposed to the same implanted (210)Po activity. The field phase of the intercomparison found excellent agreement between the track density rates for the two types of retrospective detectors. The correlation between the track density rates and direct contemporary radon concentration measurements was relatively high, considering that no adjustments were performed to account for either the residential depositional environment or glass surface type. Preliminary comparisons of the models used to translate track rate densities to average long-term radon concentrations differ between the two studies. Further calibration of the retrospective detectors' models for interpretation of track rate density may allow the pooling of studies that use glass-based retrospective radon detectors to determine historic residential radon exposures.

The Agricultural Health Study.

The Agricultural Health Study, a large prospective cohort study has been initiated in North Carolina and Iowa. The objectives of this study are to: 1) identify and quantify cancer risks among men, women, whites, and minorities associated with direct exposure to pesticides and other agricultural agents; 2) evaluate noncancer health risks including neurotoxicity reproductive effects, immunologic effects, nonmalignant respiratory disease, kidney disease, and growth and development among children; 3) evaluate disease risks among spouses and children of farmers that may arise from direct contact with pesticides and agricultural chemicals used in the home lawns and gardens, and from indirect contact, such as spray drift, laundering work clothes, or contaminated food or water; 4) assess current and past occupational and nonoccupational agricultural exposures using periodic interviews and environmental and biologic monitoring; 5) study the relationship between agricultural exposures, biomarkers of exposure, biologic effect, and genetic susceptibility factors relevant to carcinogenesis; and 6) identify and quantify cancer and other disease risks associated with lifestyle factors such as diet, cooking practices, physical activity, smoking and alcohol consumption, and hair dye use. In the first year of a 3-year enrollment period, 26,235 people have been enrolled in the study, including 19,776 registered pesticide applicators and 6,459 spouses of registered farmer applicators. It is estimated that when the total cohort is assembled in 1997 it will include approximately 75,000 adult study subjects. Farmers, the largest group of registered pesticide applicators comprise 77% of the target population enrolled in the study. This experience compares favorably with enrollment rates of previous prospective studies.

Factors associated with self-reported, pesticide-related visits to health care providers in the agricultural health study.

To investigate factors associated with pesticide-related visits to health care providers (i.e., doctor or hospital visits), responses to self-administered questionnaires received from 35,879 licensed restricted-use pesticide applicators participating in the Agricultural Health Study were analyzed. (In Iowa, applicators are actually certified, whereas in North Carolina they are licensed; for ease of reference, the term license will be used for both states in this paper.) The cohort reported a total of more than 10.9 million pesticide-application days. These applications were associated with one or more pesticide-related health care visits by 2,214 applicators (7.0% of the applicator cohort for whom health care visit data were available). The odds of a pesticide-related health care visit were increased for commercial applicators compared to private applicators [odds ratio (OR = 1.77; 95% confidence interval (CI), 1.52-2.06) and for applicators who used insecticides 70 times or more in their lifetime compared to those who used insecticides less frequently (OR = 1.43; CI, 1.26-1.63). After adjusting for the number of applications in a logistic regression model, significantly higher odds of health care visits were observed among North Carolina applicators compared to Iowa applicators (OR = 1.35; CI, 1.17-1.52), among applicators who mixed their own pesticides (OR = 1.65; CI, 1. 22-2.23), and among applicators who personally repaired their pesticide application equipment at least once per year (OR = 1.12; CI, 1.06-1.25). Significantly lower odds were found among female versus male applicators (OR = 0.68; CI, 0.46-0.99) and among applicators who graduated from high school versus those who did not (OR = 0.82; CI, 0.71-0.94 for high school graduates and OR = 0.79; CI, 0.68-0.91 for those with at least some college). Several methods of pesticide application to crops, seed, or stored grain were also associated with significantly elevated odds ratios of health care visits. These observations suggest that several steps can be taken to reduce the number of health care visits resulting from occupational exposure to pesticides. The implications of this pattern of pesticide-related health care visits may have etiologic implications for cancer and other chronic diseases.

Estimating the effect of dietary fat on the risk of lung cancer in nonsmoking women.

In 1992, approximately 13 000 lung cancers occurred in nonsmoking U.S. women but the cause of these highly fatal tumors is not well understood. As the rate of smoking declines in many developed countries, the interest in identifying lung cancer risk factors other than tobacco smoking is increasing. A population-based, case-control study of incident lung cancer among nonsmoking women in Missouri was conducted between 1986 and 1992 to assess the effect of a comprehensive list of potential risk factors. Dietary information on 429 case subjects and 1021 control subjects was obtained by personal interview, or next-of-kin interviews (36% and 64%, respectively) and the relationship of diet to lung cancer risk is the focus of this investigation. Odds ratios and population attributable risks (PAR) for dietary fat and dietary saturated fat were computed among lifetime nonsmokers and long-term ex-smokers. The mean age at lung cancer diagnosis was 71 years old, and nearly 50% of the lung cancers were histologically confirmed adenocarcinomas. Dietary intake of saturated fat was the leading identified cause of lung cancer among lifetime nonsmokers and former smokers in Missouri. The etiologic link between dietary saturated fat and lung cancer has not been examined in many other studies and the studies published to date are not completely consistent with the hypothesis so a cautious interpretation of the population attributable risks for these exposures is warranted. Nonetheless, a growing number of studies arising from around the world purport to show a link between fat, saturated fat and/or cholesterol or food groups containing relatively high amounts of these macronutrients (i.e. dairy products, eggs and/or red meat consumption) and lung cancer, and these recent studies add support to this hypothesis. If the results from Missouri are valid and applicable to other Americans, 23% of lung cancer cases among lifetime nonsmokers in the United States could be prevented if the saturated fat consumption of the upper half of saturated fat intake continuum could be reduced to the level consumed by the lower half. Even greater reductions in risk could be achieved if saturated fat consumption were reduced to even lower levels (i.e. 20th percentile of consumption as shown in this paper). However, additional etiologic research and evaluation is needed before specific dietary recommendations concerning fat and saturated fat and lung cancer prevention can be made.

Lung cancer risk and red meat consumption among Iowa women.

OBJECTIVE: Some epidemiologic studies suggest that diets high in total fat, saturated fat, or cholesterol are associated with increased risk of lung cancer. Others suggest that diets high in red meat consumption, particularly well-done red meat, are a lung cancer risk factor. In Iowa, we had the opportunity to investigate concurrently the role of meat intake and macronutrients in lung cancer etiology. METHODS: A population-based case-control study of both non-smoking and smoking women was conducted in Iowa. A 70-item food frequency questionnaire (FFQ) was completed by 360 cases and 574 frequency-matched controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression. Multivariate models included age, education, pack-years of smoking, yellow-green vegetable intake, fruit/fruit juice intake, nutrient density calories, previous non-malignant lung disease, alcohol consumption and body mass index (BMI). RESULTS: When comparing the fifth (highest) to the first (lowest) quintile of consumption of total fat, saturated fat and cholesterol, we obtained odds ratios of 2.0 (1.3-3.1), 3.0 (1.9-4.7), and 2.0 (1.3-3.0) respectively. However, when red meat was entered into the model along with total fat, saturated fat or cholesterol, the excess risk for the macronutrients disappeared while an odds ratio of 3.3 (1.7-7.6) was obtained for red meat. The odds ratios for red meat consumption were similar among adenocarcinoma cases, OR=3.0 (1.1-7.9) and non-adenocarcinoma cases, OR=3.2 (1.3-8.3) and among life-time nonsmokers and ex-smokers OR=2.8 (1.4-5.4), and current smokers, OR=4.9 (1.1-22.3). Yellow-green vegetables were protective with an odds ratio of 0.4 (0.2-0.7). CONCLUSIONS: Consumption of red meat, was associated with an increased risk of lung cancer even after controlling for total fat, saturated fat, cholesterol, fruit, yellow-green vegetable consumption and smoking history, while yellow-green vegetables are associated with a decreased risk of lung cancer.

Reliability of passive smoke exposure histories in a case-control study of lung cancer.

Despite the growing number of studies on the health effects of passive smoke exposure, few data exist on the quality of questionnaire data on passive smoking. To measure the reliability of passive smoking histories, re-interviews were conducted for 110 subjects (37 cases and 73 controls) as part of a larger study of lung cancer among non-smoking women in Missouri. Agreement was high both for parental smoking status (94% concordance; kappa = 0.82) and for spousal smoking status (84% concordance; kappa = 0.67). Concordance also was relatively high for cigarette pack-years of exposure due to the parents or spouse. Reliability tended to be somewhat higher among controls than among cases, and for exposure due to a parent or spouse than for that due to other household members. Questions on the perceived harmfulness of passive smoke exposure showed no differences between cases and controls. These findings indicate a high degree of repeatability in responses regarding passive smoking, but also suggest the potential for misclassification of passive smoke exposure status, the desirability of standardized questions on passive smoking, and the need for additional studies of reliability and validity.

Family history of cancer and risk of lung cancer in lifetime non-smokers and long-term ex-smokers.

BACKGROUND: Genetic factors appear to play a role in the aetiology of lung cancer. METHODS: To examine the association between family history of cancer (all types) and risk of lung cancer among non-smokers, we conducted a case-control study. Cases (n = 618) were identified through the Missouri Cancer Registry for the period 1986 through 1991, and included 432 lifetime non-smokers and 186 ex-smokers who had stopped at least 15 years prior to diagnosis or had smoked for less than one pack-year. Controls (n = 1402) were selected through drivers licence and Medicare files. RESULTS: The risk of lung cancer increased directly in relation to the number of family members affected with cancer. The odds ratio (OR) associated with five or more first-degree relatives with cancer was 2.7 (95% confidence interval [CI] 1.2-6.1), with a significant linear trend in risk according to the number of relatives affected (P = 0.03). Increased lung cancer risk was associated with two or more affected siblings (OR = 1.4; 95% CI: 1.0-1.9) and with two or more affected offspring (OR = 3.2: 95% CI: 1.3-8.1). Risk was slightly elevated for family history of lung cancer (OR = 1.3; 95% CI: 1.0-1.8). CONCLUSIONS: Our study identified a slight increase in risk of lung cancer in relation to five or more relatives with cancer. Preventive implications of this increased risk are unclear because the attributable fraction is low in comparison to a variety of other factors.