Evidence secondhand smoke causes breast cancer in 2005 stronger than for lung cancer in 1986

OBJECTIVES

To compare the strength of evidence from epidemiologic studies of secondhand smoke of the US Surgeon General's 1986 conclusion that secondhand smoke caused lung cancer with the California Environmental Protection Agency's (CalEPA) similar 2005 conclusion on breast cancer in younger, primarily premenopausal women.

METHODS

We reviewed each report for criteria used to assess causality: numbers of studies, statistically significant increases in risk, and pooled summary risk estimates.

RESULTS

Both the Surgeon General and CalEPA used updated Bradford Hill criteria for assessing causality and found that the evidence met those criteria. Six of 13 lung cancer studies (46%) had statistically significant increases (one of three cohort studies). Pooled risk estimates for lung cancer for spousal exposure were 1.53 for 10 combined case-control studies and 1.88 for seven studies with dose-response results. The CalEPA reported 10 of 14 studies (71%) had statistically significant increases in breast cancer risk (two of four cohort studies). Pooled relative risk estimates for younger, primarily premenopausal women were 1.68 (95% CI: 1.33, 2.12) for all exposed women and 2.19 (1.68, 2.84) for five studies with better exposure assessment.

CONCLUSIONS

The evidence from epidemiologic studies of secondhand smoke in 2005 for breast cancer in younger, primarily premenopausal women was stronger than for lung cancer in 1986.

The association between exposure to environmental tobacco smoke and breast cancer: a review by the California Environmental Protection Agency

BACKGROUND

The California Environmental Protection Agency (Cal/EPA) recently completed a health effects assessment of exposure to environmental tobacco smoke (ETS) which resulted in California listing ETS as a Toxic Air Contaminant in January 2006. As part of the assessment, studies on the association between exposure to ETS and breast cancer were reviewed.

METHODS

Twenty-six published reports (including 3 meta-analyses) evaluating the association between ETS exposure and breast cancer were reviewed. A weight-of-evidence approach was applied to evaluate the data and draw conclusions about the association between breast cancer and ETS exposure.

RESULTS

The published data indicate an association between ETS and breast cancer in younger primarily premenopausal women. Thirteen of 14 studies (10 case-control and four cohort) that allowed analysis by menopausal status reported elevated risk estimates for breast cancer in premenopausal women, seven of which were statistically significant. Our meta-analyses indicated elevated summary relative risks ranging from OR 1.68 (95% C.I. 1.31, 2.15) for all 14 studies to 2.20 (95% C.I. 1.69, 2.87) for those with the best exposure assessment.

CONCLUSIONS

Cal/EPA concluded that regular ETS exposure is causally related to breast cancer diagnosed in younger, primarily premenopausal women and that the association is not likely explained by bias or confounding.

Volumetric and areal bone mineral density measures are associated with cardiovascular disease in older men and women: the health, aging, and body composition study

The associations of volumetric (vBMD) and areal (aBMD) bone mineral density measures with prevalent cardiovascular disease (CVD) and subclinical peripheral arterial disease (PAD) were investigated in a cohort of older men and women enrolled in the Health, Aging, and Body Composition Study. Participants were 3,075 well-functioning white and black men and women (42% black, 51% women), aged 68-80 years. Total hip, femoral neck, and trochanter aBMD were measured using dual-energy X-ray absorptiometry. Quantitative computed tomography was used to evaluate spine trabecular, integral, and cortical vBMD measures in a subgroup (n = 1,489). Logistic regression was performed to examine associations of BMD measures with CVD and PAD. The prevalence of CVD (defined by coronary heart disease, PAD, cerebrovascular disease, or congestive heart failure) was 29.8%. Among participants without CVD, 10% had subclinical PAD (defined as ankle-arm index <0.9). Spine vBMD measures were inversely associated with CVD in men (odds ratio of integral [OR(integral)] = 1.34, 95% confidence interval [CI] 1.10-1.63; OR(trabecular )= 1.25, 95% CI 1.02-1.53; OR(cortical )= 1.36, 95% CI 1.11-1.65). In women, for each standard deviation decrease in integral vBMD, cortical vBMD, or trochanter aBMD, the odds of CVD were significantly increased by 28%, 27%, and 22%, respectively. Total hip aBMD was associated with subclinical PAD in men (OR = 1.39, 95% CI 1.03-1.84) but not in women. All associations were independent of age and shared risk factors between BMD and CVD and were not influenced by inflammatory cytokines (interleukin-6 and tumor necrosis factors-alpha). In conclusion, our results provide further evidence for an inverse association between BMD and CVD in men and women. Future research should investigate common pathophysiological links for osteoporosis and CVD.

Chlorination disinfection by-products in drinking water and the risk of adult leukemia in Canada

The authors conducted a population-based case-control study of 1,068 incident leukemia cases and 5,039 controls aged 20-74 years during 1994-1997 to examine the association between exposure to drinking water chlorination disinfection by-products and adult leukemia risk in Canada. Residence and drinking water source histories and data from municipal water supplies were used to estimate individual chlorination disinfection by-product exposure according to water source, chlorination status, and chlorination disinfection by-product levels during the 40-year period before the interview. The analysis included 686 cases and 3,420 controls for whom water quality information was available for at least 30 of these years. Increased risk of chronic myeloid leukemia was associated with increasing years of exposure to different chlorination disinfection by-product indexes, with an adjusted odds ratio of 1.72 (95% confidence interval: 1.01, 3.08) for the highest exposure duration to total trihalomethanes of more than 40 microg/liter. In contrast, the risk of the other studied leukemia subtypes was found to decrease with increasing years of exposure to chlorination disinfection by-products. A protective effect was noted for chronic lymphoid leukemia (odds ratio = 0.60, 95 percent confidence interval: 0.41, 0.87) associated with the highest exposure duration to total trihalomethanes of more than 40 microg/liter. More studies with long-term exposure measures and large enough to evaluate leukemia subtypes are needed to further understanding of the issue.

Cross-sectional correlates of fasting hyperinsulinaemia in post-menopausal women of different ethnic origin

AIMS

In a large ethnically diverse nationwide sample of post-menopausal women we explored the relationship between fasting insulin levels, ethnicity, and a wide range of anthropometric, socio-economic, and lifestyle factors.

METHODS

Subjects were post-menopausal women aged 50-79 years without diagnosed diabetes mellitus comprising a subsample (n = 3500) of the Women's Health Initiative (WHI) Clinical Trial and Observational Study. In a cross-sectional survey at baseline, we analysed the association between ethnicity and fasting insulin using analysis of covariance procedures and identified independent correlates of hyperinsulinaemia, defined by the 75th percentile cut point for each ethnic group.

RESULTS

Fasting insulin levels were higher among African-American and Hispanic women than among non-Hispanic White or Asian women. These differences persisted after adjustment for age, educational attainment, total and central body obesity, adult weight change, family history of diabetes, smoking status, alcohol consumption, use of menopausal hormone therapy and physical activity. Higher levels of body mass index, waist-hip ratio, adult weight gain, and lower levels of total and moderate or strenuous recreational activity were independent correlates of fasting hyperinsulinaemia. Habitual walking was also inversely associated with fasting insulin.

CONCLUSIONS

In this cross-sectional analysis, fasting insulin levels were higher among African-American and Hispanic post-menopausal women as compared with non-Hispanic White and Asian women. In addition, obesity, adult weight gain, and low levels of moderate or strenuous physical activity were independently associated with hyperinsulinaemia.

Lifestyle factors and the risk of adult leukemia in Canada

OBJECTIVES

To evaluate the impact of active smoking, obesity, and dietary intakes on the risk of adult leukemia.

METHODS

We analysed data obtained from a population-based case-control study conducted in eight Canadian provinces. Risk estimates were generated by applying multivariate logistic regression methods to 1068 incident histologically confirmed leukemia cases and 5039 controls aged 20-74.

RESULTS

We found a statistically significant increased risk for acute myeloid leukemia (AML) associated with active smoking, with a clear dose-response relationship and an adjusted odds ratio (OR) of 1.5 (95% confidence interval [CI]=1.1-2.0) for heavy smokers reporting more than 20 pack-years of cigarette smoking. We also observed positive associations with the highest body mass index (BMI) for AML, chronic myeloid leukemia, and chronic lymphoid leukemia with a significant dose-response relationship. No association with leukemia was observed for the intake of fruits and vegetables, and the effect of active smoking on adult leukemia risk was not modified by fruits and/or vegetables consumption or obesity. However, the positive risk for AML associated with active smoking disappeared among subjects with high BMI (> or =30 kg/m2).

CONCLUSIONS

Our study contributes to the accumulating evidence linking AML and active smoking, and provides some evidence that obesity increases the risk of most of the adult leukemia subtypes.

Accumulating evidence on passive and active smoking and breast cancer risk

The aim of the study was to examine the risk of breast cancer associated with passive and active smoking and to explore risk heterogeneity among studies. Nineteen of 20 located published studies of passive smoking and breast cancer risk among women met basic quality criteria. Pooled relative risk estimates for breast cancer were calculated for 1) life-long non-smokers with regular passive exposure to tobacco smoke and 2) women who smoked. They were compared to women categorized as never regularly exposed to tobacco smoke. The pooled risk estimate for breast cancer associated with passive smoking among life-long non-smokers was 1.27 (95% confidence interval (CI), 1.11-1.45). In the subset of 5 studies (all case-control studies) with more complete exposure assessment (quantitative long-term information on the 3 major sources of passive smoke exposure: childhood, adult residential and occupational), the pooled risk estimate for exposed non-smokers was 1.90 (95%CI, 1.53-2.37). For the 14 studies with less complete passive exposure measures the risk was 1.08 (95%CI, 0.99-1.19) overall, 1.16 for 7 case-control and 1.06 for 7 cohort studies, although dose-response results in 3 of 4 Asian cohort studies suggested increased risk. The overall premenopausal breast cancer risk associated with passive smoking among life-long non-smokers was 1.68 (95%CI 1.33-2.12), and 2.19 (95% CI 1.68-2.84) for the 5 of 14 studies with more complete exposure assessment. For women who had smoked the breast cancer risk estimate was 1.46 (95%CI 1.15-1.85) when compared to women with neither active nor regular passive smoke exposure; 2.08 (95% CI 1.44-3.01) for more complete and 1.15 (95% CI 0.92-1.43) for less complete passive exposure assessment. Studies with thorough passive smoking exposure assessment implicate passive and active smoking as risk factors for premenopausal breast cancer. Cohort studies with thorough passive smoking assessment would be helpful and studies exploring biological mechanisms are needed to explain the unexpected similarity of the passive and active risks.

Environmental Tobacco Smoke and Risk of Adult Leukemia

BACKGROUND

The role of environmental tobacco smoke (ETS) in the causation of lung and breast cancer has been repeatedly evaluated over recent years. In contrast, its impact on the risk of adult leukemia has received little attention.

METHODS

We used the lifetime residential and occupational ETS exposure histories from a population-based sample of 1068 incident and histologically confirmed adult leukemia cases and 5039 population controls age 20 to 74 years to evaluate the relationship between ETS exposure and adult leukemia risk among nonsmokers in Canada. The duration of exposure and smoker-years index were used as indices of ETS exposure. We restricted our analysis to the 266 case and 1326 control subjects who reported being lifetime nonsmokers and provided residential ETS exposure history for at least 75% of their lifetime.

RESULTS

No association was found for most leukemia subtypes, and in particular for acute myeloid leukemia. In contrast, the risk for chronic lymphocytic leukemia was clearly associated with ETS exposure, with an adjusted odds ratio of 2.3 (95% confidence interval = 1.2-4.5) for more than 83 smoker-years of residential exposure and 2.4 (1.3-4.3) for more than 72 smoker-years of occupational exposure. There was a dose-response relationship for chronic lymphocytic leukemia with both indices of exposure. Risk was not higher with recent exposure, using time-window-exposure analyses.

CONCLUSIONS

Regular long-term ETS exposure may be a risk factor for chronic lymphocytic leukemia.

Specific fatty acid intake and the risk of pancreatic cancer in Canada

The possible association of specific fatty acid (FA) intake and pancreatic cancer risk was investigated in a population-based case–control study of 462 histologically confirmed cases and 4721 frequency-matched controls in eight Canadian provinces between 1994 and 1997. Dietary intake was assessed by means of a self-administered food frequency questionnaire. Unconditional logistic regression was used to assess associations between dietary FAs and pancreatic cancer risk. After adjustment for age, province, body mass index, smoking, educational attainment, fat and total energy intake, statistically significant inverse associations were observed between pancreatic cancer risk and palmitate (odds ratios (ORs)=0.73; 95% confidence intervals (CIs) 0.56–0.96; P-trend=0.02), stearate (OR=0.70; 95% CI 0.51–0.94; P-trend=0.04), oleate (OR=0.75; 95% CI 0.55–1.02; P-trend=0.04), saturated FAs (OR=0.67; 95% CI 0.50–0.91; P-trend=0.01), and monounsaturated FAs (OR=0.72; 95% CI 0.53–0.98; P-trend=0.02), when comparing the highest quartile of intake to the lowest. Significant interactions were detected between body mass index and both saturated and monounsaturated FAs, with a markedly reduced risk associated with intake of stearate (OR=0.36; 95% CI 0.18–0.70; P-trend=0.001), oleate (OR=0.36; 95% CI 0.19–0.72; P-trend=0.002), saturated FAs (OR=0.35; 95% CI 0.18–0.67; P-trend=0.002), and monounsaturated FAs (OR=0.32; 95% CI 0.16–0.63; P-trend<0.0001) among subjects who are obese. The results suggest that substituting polyunsaturated FAs with saturated or monounsaturated FAs may reduce pancreatic cancer risk, independently of total energy intake, particularly among obese subjects.

Chlorination disinfection by-products and pancreatic cancer risk

Chlorination disinfection by-products (CDBPs) are produced during the treatment of water with chlorine to remove bacterial contamination. CDBPs have been associated with an increased risk of bladder cancer. There is also some evidence that they may increase the risk of pancreatic cancer. We report results from a population-based case-control study of 486 incident cases of pancreatic cancer and 3,596 age- and sex-matched controls. Exposure to chlorination by-products was estimated by linking lifetime residential histories to two different databases containing information on CDBP levels in municipal water supplies. Logistic regression analysis found no evidence of increased pancreatic cancer risk at higher CDBP concentrations (all odds ratios < 1.3). Null findings were also obtained assuming a latency period for pancreatic cancer induction of 3, 8, or 13 years.

Dietary intake of lycopene is associated with reduced pancreatic cancer risk

Although fruits and vegetables have been implicated in the etiology of pancreatic cancer, the role of phytochemicals in these food groups has received little attention to date. In this study, we investigated the possible association between dietary carotenoids and pancreatic cancer risk. A case-control study of 462 histologically confirmed pancreatic cancer cases and 4721 population-based controls in 8 Canadian provinces took place between 1994 and 1997. Dietary intake was assessed by a self-administered FFQ. Unconditional logistic regression was used to assess associations between specific and total carotenoid intakes and the risk of pancreatic cancer. All tests of statistical significance were 2-sided. After adjustment for age, province, BMI, smoking, educational attainment, dietary folate, and total energy intake, lycopene, provided mainly by tomatoes, was associated with a 31% reduction in pancreatic cancer risk among men [odds ratio (OR) = 0.69; 95% CI: 0.46-0.96; P = 0.026 for trend] when comparing the highest and lowest quartiles of intake. Both beta-carotene (OR = 0.57; 95% CI: 0.32-0.99; P = 0.016 for trend) and total carotenoids (OR = 0.58; 95% CI: 0.34-1.00; P = 0.02 for trend) were associated with a significantly reduced risk among those who never smoked. The results of this study suggest that a diet rich in tomatoes and tomato-based products with high lycopene content may help reduce pancreatic cancer risk.

Dietary patterns and risk of pancreatic cancer

To investigate associations between broad dietary patterns and pancreatic cancer risk, we conducted a case-control study of 585 histologically confirmed pancreatic cancer cases and 4,779 population-based controls in 8 Canadian provinces between 1994 and 1997. Dietary intake was assessed using a FFQ. Major dietary patterns were identified by factor analysis. Unconditional logistic regression was used to describe associations between dietary pattern scores and risk of pancreatic cancer. Three dietary patterns were identified: Western, characterized by high intake of processed meats, sweets and desserts, refined grains and potatoes; fruits and vegetables, characterized by high intake of fresh fruits and cruciferous vegetables; drinker, characterized by high consumption of liquor, wine and beer. After adjustment for age, BMI, smoking, physical activity, province, educational attainment and total energy intake, the fruits and vegetables pattern was associated with a 49% reduction in pancreatic risk among men (OR = 0.51, 95% CI 0.29-0.90, p = 0.004) when comparing the highest and lowest quartiles of dietary pattern scores. No significant relationship was observed with the Western and drinker patterns. Although the response rate for eligible, recruited subjects was relatively low, our results suggest that the fruits and vegetables dietary pattern reduces pancreatic cancer risk among men.

A case?control study of occupational risk factors for bladder cancer in Canada

OBJECTIVE

To investigate occupational risk factors for bladder cancer in seven Canadian provinces.

METHODS

We analysed a population-based case-control dataset of 887 individuals with incident, histologically confirmed bladder cancer between 1994 and 1997. Controls (2847) frequency matched for age and gender were surveyed in 1996. Questionnaires were returned by about 60% of subjects. Odds ratios (ORs) for occupations and self-reported exposures were adjusted for province, age, race, smoking, and several dietary factors, using unconditional logistic regression.

RESULTS

Statistically significant increased risks were observed among men employed as hairdressers (OR = 3.42; 1.09-10.8), primary metal workers (OR = 2.40; 1.29-4.50), miners (OR = 1.94; 1.18-3.17), and automechanics (OR = 1.69; 1.02-2.82). Primary metal workers and automechanics showed evidence of an employment duration-response trend. Modest elevated risks that were not significant were also observed for male government inspectors, printers, firefighters, general labourers, and welders. A duration-response trend was evident for government inspectors and general labourers. For females, significant elevations were observed among lumber processors (OR = 8.78; 1.28-60.1), general labourers (OR = 2.18; 1.05-4.52), nurses (OR = 1.54; 1.03-2.31), and general clerks (OR = 1.48; 1.01-2.17). The latter showed a positive duration-response trend.

CONCLUSIONS

This study found a statistically significant excess risk of bladder cancer, with a duration-response trend, among male primary metal workers and automechanics, and female office workers engaged in general clerical duties.

A Case-Control Study of Diet and the Risk of Ovarian Cancer

Epidemiologic studies have suggested that some dietary factors may play a role in the etiology of ovarian cancer, but the findings have been inconsistent. We assessed the association of ovarian cancer with dietary factors in a population-based case-control study in Canada. Diet information was collected on 442 incident cases of ovarian cancer diagnosed in 1994 to 1997 and 2,135 population controls via a self-administered questionnaire. Compared with women in the lowest quartile of cholesterol intake, those in the second, third, and fourth quartiles had a multivariate adjusted odds ratio [OR; 95% confidence interval (95% CI)] of 1.12 (0.81–1.56), 1.20 (0.85–1.68), and 1.42 (1.03–1.97), respectively (P for trend = 0.031). Higher egg consumption was also associated with a nonsignificant increase in ovarian cancer risk. The ORs (95% CIs) for ovarian cancer were 0.77 (0.60–1.04) and 0.76 (0.56–0.99) among women in the highest quartile of total vegetable and cruciferous vegetable intake as compared with women in the lowest quartile. Women who took supplements of vitamin E, β-carotene, and B-complex vitamins for ≥10 years had ORs (95% CIs) of 0.49 (0.30–0.81), 0.31 (0.11–0.91), and 0.61 (0.36–1.05), respectively. However, we did not observe an association of ovarian cancer risk with dietary fat intake, including saturated, monounsaturated, and polyunsaturated fatty acids, protein, carbohydrate, dietary fiber, fruit, dairy products, meat products, fish, chicken, grain products, nut products, baked desserts, margarine, butter, mayonnaise, and supplement of multiple vitamins, vitamin A, vitamin C, calcium, iron, zinc, and selenium. Our findings suggested that ovarian cancer risk was positively associated with higher consumption of dietary cholesterol and eggs and inversely associated with higher intake of total vegetables and cruciferous vegetables and supplementation of vitamin E, β-carotene, and B-complex vitamins.

A case-control study of diet and the risk of ovarian cancer

Epidemiologic studies have suggested that some dietary factors may play a role in the etiology of ovarian cancer, but the findings have been inconsistent. We assessed the association of ovarian cancer with dietary factors in a population-based case-control study in Canada. Diet information was collected on 442 incident cases of ovarian cancer diagnosed in 1994 to 1997 and 2,135 population controls via a self-administered questionnaire. Compared with women in the lowest quartile of cholesterol intake, those in the second, third, and fourth quartiles had a multivariate adjusted odds ratio [OR; 95% confidence interval (95% CI)] of 1.12 (0.81-1.56), 1.20 (0.85-1.68), and 1.42 (1.03-1.97), respectively (P for trend = 0.031). Higher egg consumption was also associated with a nonsignificant increase in ovarian cancer risk. The ORs (95% CIs) for ovarian cancer were 0.77 (0.60-1.04) and 0.76 (0.56-0.99) among women in the highest quartile of total vegetable and cruciferous vegetable intake as compared with women in the lowest quartile. Women who took supplements of vitamin E, beta-carotene, and B-complex vitamins for > or =10 years had ORs (95% CIs) of 0.49 (0.30-0.81), 0.31 (0.11-0.91), and 0.61 (0.36-1.05), respectively. However, we did not observe an association of ovarian cancer risk with dietary fat intake, including saturated, monounsaturated, and polyunsaturated fatty acids, protein, carbohydrate, dietary fiber, fruit, dairy products, meat products, fish, chicken, grain products, nut products, baked desserts, margarine, butter, mayonnaise, and supplement of multiple vitamins, vitamin A, vitamin C, calcium, iron, zinc, and selenium. Our findings suggested that ovarian cancer risk was positively associated with higher consumption of dietary cholesterol and eggs and inversely associated with higher intake of total vegetables and cruciferous vegetables and supplementation of vitamin E, beta-carotene, and B-complex vitamins.

Association of cigarette smoking with the risk of ovarian cancer

Cigarette smoking may be associated with ovarian cancer risk. This association may differ by histological type. The authors conducted a population-based case-control study in Canada of 442 incident cases of ovarian cancer and 2,135 controls 20-76 years of age during 1994-1997 to examine this association, overall and by histological type. Compared to women who never smoked, those who smoked had higher odds (odds ratio [OR] = 1.22; 95% confidence interval [CI] = 0.98-1.53) of having ovarian cancer, and the OR was larger for ex-smokers (1.30; 95% CI = 1.01-1.67) than for current smokers (1.10; 95% CI = 0.81-1.49). The association with cigarette smoking was stronger for mucinous tumors (OR = 1.77; 95% CI = 1.06-2.96) than for nonmucinous tumors (OR = 1.13; 95% CI = 0.89-1.44). In addition, the odds of smokers having mucinous tumors increased with years of smoking (OR = 1.36, 1.88, 1.19, 4.89 for <20, 21-30, 31-40 and >40 years, respectively; p for trend = 0.002), number of cigarettes smoked per day (OR = 1.55, 1.89, 2.28 for <10, 11-20 and >20 cigarettes/day, respectively; p for trend = 0.014) and smoking pack-years (OR = 1.13, 2.65, 1.77 and 2.39 for <10, 11-20, 21-30 and >30 pack-years, respectively; p for trend = 0.004). Our data suggest that cigarette smoking is associated with an increased risk of ovarian cancer, especially for mucinous types.

Dietary Fish Intake and Risk of Leukaemia, Multiple Myeloma, and Non-Hodgkin Lymphoma

This study aimed to determine whether fish intake was protective against leukemia, multiple myeloma, and non-Hodgkin lymphoma (NHL), and if our previous finding of a protective effect of fish-related occupations on the risk of these diseases was due to dietary intake of fish. We used data from a population-based case-control study undertaken in Canada in 1994–1998. Dietary information was available for 919 leukemia cases, 287 myeloma cases, 1418 NHL cases, and 4202 controls. The risk of each of the three cancers was determined using multiple logistic regression analysis according to quartiles of weekly fresh fish intake, percentage of total energy intake from fresh fish, and percentage of total fat intake from fresh fish. After adjusting for age, sex, smoking, BMI, and proxy status, people who consumed greater proportions of their total energy intake from fresh fish had a significantly lower risk of each of the three types of cancer, and there was a significant dose-response for risk of leukemia and NHL. Those in the highest quartile for percentage of fat intake from fish were at lowest risk: leukemia odds ratio (OR) 0.72, 95% confidence interval (CI) 0.58–0.89; multiple myeloma OR 0.64, 95% CI 0.45–0.90; NHL OR 0.71, 95% CI 0.60–0.85; and all LH cancers combined OR 0.70, 95% CI 0.61–0.81. The protective effect previously observed for working with fish on the risk of leukemia and lymphoma was independent of fish intake. These findings suggest that a diet high in fish may be protective against lymphohematopoietic cancers and confirm the reduced risk among fish workers.

Dietary fish intake and risk of leukaemia, multiple myeloma, and non-Hodgkin lymphoma

This study aimed to determine whether fish intake was protective against leukemia, multiple myeloma, and non-Hodgkin lymphoma (NHL), and if our previous finding of a protective effect of fish-related occupations on the risk of these diseases was due to dietary intake of fish. We used data from a population-based case-control study undertaken in Canada in 1994-1998. Dietary information was available for 919 leukemia cases, 287 myeloma cases, 1418 NHL cases, and 4202 controls. The risk of each of the three cancers was determined using multiple logistic regression analysis according to quartiles of weekly fresh fish intake, percentage of total energy intake from fresh fish, and percentage of total fat intake from fresh fish. After adjusting for age, sex, smoking, BMI, and proxy status, people who consumed greater proportions of their total energy intake from fresh fish had a significantly lower risk of each of the three types of cancer, and there was a significant dose-response for risk of leukemia and NHL. Those in the highest quartile for percentage of fat intake from fish were at lowest risk: leukemia odds ratio (OR) 0.72, 95% confidence interval (CI) 0.58-0.89; multiple myeloma OR 0.64, 95% CI 0.45-0.90; NHL OR 0.71, 95% CI 0.60-0.85; and all LH cancers combined OR 0.70, 95% CI 0.61-0.81. The protective effect previously observed for working with fish on the risk of leukemia and lymphoma was independent of fish intake. These findings suggest that a diet high in fish may be protective against lymphohematopoietic cancers and confirm the reduced risk among fish workers.

Environmental tobacco smoke and the risk of pancreatic cancer: findings from a Canadian population-based case-control study

BACKGROUND

Despite the fact that tobacco is a well-recognized risk factor for pancreatic cancer, no study has yet reported on the association between environmental tobacco smoke (ETS) and this malignancy. We investigated the relationship between pancreatic cancer and childhood and adult exposure to ETS using a case-control study design.

METHODS

Our study population consisted of 583 pancreatic cancer cases and 4,813 population-based controls that were identified within 8 Canadian provinces between 1994 and 1997. Mail-out questionnaires were used to collect risk factor information and a lifetime residential and occupational history of exposure to ETS.

RESULTS

Among never smokers, those who were exposed to ETS both as a child and as an adult had an odds ratio of 1.21 (95% CI=0.60-2.44) relative to those with no exposure. For active smoking, when the referent group consisted of never smokers who had not been regularly exposed to ETS, the risk increases were more pronounced with an increased number of years of smoking, cigarette pack-years, years since quit smoking, and average number of cigarettes smoked daily.

CONCLUSIONS

Overall, our results are suggestive of a weak association between pancreatic cancer and ETS. Perhaps more importantly, they suggest that ETS smoking exposures may confound the risk of pancreatic cancer associated with active smoking measures commonly used in epidemiologic studies.

Residential proximity to industrial plants and non-Hodgkin lymphoma

BACKGROUND

A U.S. analysis suggested a relation between self-reported residential proximity to industrial plants and non-Hodgkin lymphoma (NHL) risk.

METHODS

Using lifetime residential histories collected from a population-based sample of 1499 Canadians with newly diagnosed, histologically confirmed NHL and 5039 population controls, we evaluated the association of residential proximity to 7 types of major heavy industry with NHL risk.

RESULTS

Overall, having lived within 0.8 km or within 3.2 km of an industrial plant was not associated with increased NHL risk. For the follicular subtype of NHL, an odds ratio (OR) of 1.48 (95% confidence interval [CI] = 1.10-1.99) was observed for women who had lived within 3.2 km (83 cases/689 controls). ORs for NHL were elevated for proximity within 3.2 km of copper smelters (OR = 5.1; CI = 1.5-17.7; 7 cases, 4 controls) and within 0.8 km of sulfite pulp mills (OR = 3.7; CI = 1.5-9.4; 9 cases, 10 controls).

CONCLUSIONS

We have identified possible associations between NHL and proximity to industrial plants, which could be the result of chance or other factors associated with proximity. Studies are needed to confirm these associations and to determine whether residential proximity can result in meaningful exposure.

Association of obesity and cancer risk in Canada

The authors conducted a population-based, case-control study of 21,022 incident cases of 19 types of cancer and 5,039 controls aged 20-76 years during 1994-1997 to examine the association between obesity and the risks of various cancers. Compared with people with a body mass index of less than 25 kg/m(2), obese (body mass index of > or = 30 kg/m(2)) men and women had an increased risk of overall cancer (multivariable adjusted odds ratio = 1.34, 95% confidence interval (CI): 1.22, 1.48), non-Hodgkin's lymphoma (odds ratio = 1.46, 95% CI: 1.24, 1.72), leukemia (odds ratio = 1.61, 95% CI: 1.32, 1.96), multiple myeloma (odds ratio = 2.06, 95% CI: 1.46, 2.89), and cancers of the kidney (odds ratio = 2.74, 95% CI: 2.30, 3.25), colon (odds ratio = 1.93, 95% CI: 1.61, 2.31), rectum (odds ratio = 1.65, 95% CI: 1.36, 2.00), pancreas (odds ratio = 1.51, 95% CI: 1.19, 1.92), breast (in postmenopausal women) (odds ratio = 1.66, 95% CI: 1.33, 2.06), ovary (odds ratio = 1.95, 95% CI: 1.44, 2.64), and prostate (odds ratio = 1.27, 95% CI: 1.09, 1.47). Overall, excess body mass accounted for 7.7% of all cancers in Canada-9.7% in men and 5.9% in women. This study provides further evidence that obesity increases the risk of overall cancer, non-Hodgkin's lymphoma, leukemia, multiple myeloma, and cancers of the kidney, colon, rectum, breast (in postmenopausal women), pancreas, ovary, and prostate.

Dietary risk factors for testicular carcinoma

Although testicular cancer is a relatively rare lesion, accounting for only 1.1% of all malignant neoplasms in males in Canada, it is the most common cancer among Canadian men 20-45 years of age. Knowledge of the causes of testicular cancer risk in general, and more specifically, its association with diet, remain limited. Data from 601 cases of testicular cancer and 744 population-based controls collected in 8 of the 10 Canadian provinces between 1994-97 were used to explore the relationship between diet and testicular cancer risk. We systematically examined 17 food groups, 15 nutrients and 4 individual foods based on data collected through a 69-item food-frequency questionnaire. Our results suggest that high dairy product intake, in particular high intake of cheese (odds ratio [OR] = 1.87; 95% confidence interval [CI] 1.22-2.86; p-trend < 0.001), is associated with an elevated risk of testicular cancer in Canadian males.

Physical activity and the risk of lung cancer in Canada

A population-based case-control study of 2,128 cases with histologically confirmed incident lung cancer and 3,106 population controls aged 20-76 years was conducted to assess the impact of recreational physical activity on lung cancer risk in Canada in 1994-1997. The multivariable-adjusted odds ratios and 95% confidence intervals for the second, third, and fourth quartiles versus the lowest quartile of total recreational physical activity were, respectively, 0.82 (95% confidence interval: 0.68, 0.98), 0.76 (95% confidence interval: 0.63, 0.92), and 0.73 (95% confidence interval: 0.60, 0.89) (p for trend=0.0008). The risk reduction was observed for both men and women and was attributed to both moderate and vigorous activities. A greater risk reduction was found for squamous cell carcinoma in women, small cell carcinoma in men, and other types/unspecified histologic subtypes in both genders. The physical-activity-associated risk reduction was more profound among smokers and those with low and medium body mass indexes. This study provides additional evidence that recreational physical activity reduces lung cancer risk. More studies are needed to confirm the differences between histologic subtypes and between genders and to address the underlying biologic mechanisms.

Physical inactivity, energy intake, obesity and the risk of rectal cancer in Canada

We conducted a population-based case-control study of 1,447 incident rectal cancer cases and 3,106 population controls aged 20-76 years to assess the effect of recreational physical activity, energy intake and obesity on rectal cancer risk in 7 of 10 Canadian provinces in 1994-97. After adjustment for the effect of various potential confounding factors, total recreational physical activity in the highest quartile was associated with an odds ratio (OR) for rectal cancer risk of 0.88 (95% confidence interval [CI] = 0.64-1.20) in women and 1.15 (95% CI = 0.88-1.49) in men. Women and men in the highest quartile of caloric intake (> = 56,741 and > = 63,143 kJ/week) had ORs of 1.50 (95% CI = 1.00-2.25) and 1.61 (95% CI = 1.13-2.28), respectively. Total dietary fat intake was not associated with a risk of rectal cancer after adjustment for caloric intake. Obesity (BMI > = 30 kg/m(2)) was associated with an OR of 1.44 (95% CI = 1.06-1.95) for women and 1.78 (95% CI = 1.36-2.34) for men. Men and women with lifetime maximum body mass index (BMI) > = 30 kg/m(2) had respective ORs of 1.70 (95% CI = 1.30-2.23) and 1.26 (95% CI = 0.96-1.66). The greatest increase in rectal cancer risk was observed in men and women with simultaneous high energy intake, high BMI and low physical activity. Our study provides evidence that physical inactivity, high energy intake and obesity are associated with the risk of rectal cancer, and there is a probable synergic effect among the 3 risk factors.

Alcohol, tobacco and breast cancer--collaborative reanalysis of individual data from 53 epidemiological studies, including 58,515 women with breast cancer and 95,067 women without the disease

Alcohol and tobacco consumption are closely correlated and published results on their association with breast cancer have not always allowed adequately for confounding between these exposures. Over 80% of the relevant information worldwide on alcohol and tobacco consumption and breast cancer were collated, checked and analysed centrally. Analyses included 58,515 women with invasive breast cancer and 95,067 controls from 53 studies. Relative risks of breast cancer were estimated, after stratifying by study, age, parity and, where appropriate, women's age when their first child was born and consumption of alcohol and tobacco. The average consumption of alcohol reported by controls from developed countries was 6.0 g per day, i.e. about half a unit/drink of alcohol per day, and was greater in ever-smokers than never-smokers, (8.4 g per day and 5.0 g per day, respectively). Compared with women who reported drinking no alcohol, the relative risk of breast cancer was 1.32 (1.19-1.45, P<0.00001) for an intake of 35-44 g per day alcohol, and 1.46 (1.33-1.61, P<0.00001) for >/=45 g per day alcohol. The relative risk of breast cancer increased by 7.1% (95% CI 5.5-8.7%; P<0.00001) for each additional 10 g per day intake of alcohol, i.e. for each extra unit or drink of alcohol consumed on a daily basis. This increase was the same in ever-smokers and never-smokers (7.1% per 10 g per day, P<0.00001, in each group). By contrast, the relationship between smoking and breast cancer was substantially confounded by the effect of alcohol. When analyses were restricted to 22 255 women with breast cancer and 40 832 controls who reported drinking no alcohol, smoking was not associated with breast cancer (compared to never-smokers, relative risk for ever-smokers=1.03, 95% CI 0.98-1.07, and for current smokers=0.99, 0.92-1.05). The results for alcohol and for tobacco did not vary substantially across studies, study designs, or according to 15 personal characteristics of the women; nor were the findings materially confounded by any of these factors. If the observed relationship for alcohol is causal, these results suggest that about 4% of the breast cancers in developed countries are attributable to alcohol. In developing countries, where alcohol consumption among controls averaged only 0.4 g per day, alcohol would have a negligible effect on the incidence of breast cancer. In conclusion, smoking has little or no independent effect on the risk of developing breast cancer; the effect of alcohol on breast cancer needs to be interpreted in the context of its beneficial effects, in moderation, on cardiovascular disease and its harmful effects on cirrhosis and cancers of the mouth, larynx, oesophagus and liver.

Health Opportunities with Physical Exercise (HOPE): social contextual interventions to reduce sedentary behavior in urban settings

Physical activity interventions targeting social and physical environments of the urban poor hold promise in improving health outcomes in underserved communities. This study randomly assigned overweight, sedentary, economically disadvantaged adults to one of three intervention conditions at The Hope and Healing Center, a large inner-city health facility providing numerous options for exercise. Within the tenets of Social Action Theory, the Health Opportunities with Physical Exercise (HOPE) trial will test the efficacy of two behavior change models, social support and patient-provider interaction, to increase physical activity. In addition to a standard care condition, in which patients have open access to Hope and Healing physical activity programming, patients were assigned to one of two behavior change interventions. Those assigned to patient-peer receive face-to-face, systematic and scheduled encouragement from study-trained 'peer' interventionists at the facility. Patients assigned to patient-provider receive face-to-face, systematic and scheduled encouragement provided by study-trained 'provider' interventionists also at the facility. The primary outcomes of change in exercise behavior will be documented by self-reported physical activity and confirmed by fitness testing at baseline, 6, 12 and 24 months during the 1 year of active intervention and 1 year of relapse prevention follow-up. Intervention conditions will be compared on psychosocial mediators including motivational appraisals, ratings of social support, rapport, problem solving and self-efficacy for overcoming barriers to increased physical activity. Novel aspects of this intervention include: (1) delivery of socially based physical activity interventions to an economically disadvantaged urban population, (2) reduction of environmental barriers to be physically active and (3) emphasis on social interactions influencing health habit change. Results of this study have the potential to identify mechanisms of behavior change that could be adopted by physical activity interventions aimed at reducing sedentary behavior and health disparities in high-risk, underserved populations.

Animal-related occupations and the risk of leukemia, myeloma, and non-Hodgkin's lymphoma in Canada

OBJECTIVE

There is some evidence to suggest that workers in animal-related occupations are at increased risk of developing lymphohematopoietic cancers. This study aimed to examine the risk of leukemia, non-Hodgkin's lymphoma (NHL), and multiple myeloma associated with occupational exposure to animals.

METHODS

We used data from a multi-site, population-based case-control study using mailed questionnaires which had taken place in eight of ten Canadian provinces, during 1994-1998. There were 1023 leukemia cases, 1577 NHL cases, and 324 multiple myeloma cases (all histologically confirmed) and 4688 population-based controls. Animal-related occupations were identified from a lifetime occupational history. Subjects in animal-related jobs were compared with others using logistic regression for the risk of leukemia, NHL, and multiple myeloma.

RESULTS

Compared to subjects without occupational exposure to animals, occupational exposure to beef cattle increased the risks of leukemia (odds ratio (OR) 2.0, 95% confidence interval (CI) 1.2-3.3) and NHL (OR 1.8, 95% CI 1.1-2.9). No other animal exposure was consistently associated with risk of lymphohematopoietic cancer. An unexpected protective association was observed between work as a fisherman and leukemia (OR 0.4, 95% CI 0.2-0.8) and NHL (OR 0.6, 95% CI 0.4-0.9).

CONCLUSIONS

This population-based case-control study found that those individuals working in occupations associated with beef cattle are at increased risk for developing leukemia and lymphoma while those working in occupations requiring the handling of fish are at decreased risk of leukemia and lymphoma.

Risk factors for male breast cancer in Canada, 1994-1998

Relatively little attention has been paid to the aetiology of male breast cancer and the current understanding of female breast cancer, primarily related to reproductive events, cannot be readily transferred to understanding the cancer in males. However, since male breast cancer occurs in the absence of factors related to childbearing and menstruation, its aetiology may provide special insights into the causes of breast cancer in women. We examined lifestyle risk factors for male breast cancer as part of a Canadian, multi-site, population-based, case-control study. Eighty-one newly diagnosed, histologically confirmed cases and 1905 male controls aged 42-74 were analysed using unconditional logistic regression. Increased risks were found for men with a mother or sister with breast cancer (adjusted odds ratio (OR) 3.65, 95% confidence interval (95% CI) 1.62-8.19). Higher physical activity levels (moderate, and strenuous recreational plus occupational) were associated with a decreased risk of male breast cancer (highest quartile, adjusted OR 0.48, 95% CI 0.26-0.91). Similarly, higher risks were associated with higher weight 2 years before interview (2.19, 95% CI 1.08-4.43), maximum weight (OR 2.66) and higher body mass index (OR 1.60). Higher vegetable consumption and coffee consumption were associated with decreased risk, whereas higher beta-carotene, vitamin E and calcium supplementation were associated with statistically significant increased risk. The small number of cases and multiple comparisons preclude strong conclusions, but our study is consistent with studies suggesting obesity and family history increase risk, and physical activity decreases risk of breast cancer.

Brain cancer and occupational exposure to magnetic fields among men: results from a Canadian population-based case-control study

BACKGROUND

The relationship between occupational exposure to magnetic fields and brain cancer in men was investigated using population-based case-control data collected in eight Canadian provinces. Emphasis was placed on examining the variations in risk across different histological types.

METHODS

A list of occupations was compiled for 543 cases and 543 controls that were individually matched by age. Occupations were categorized according to their average magnetic field exposure through blinded expert review (<0.3, 0.3-<0.6, and > or = 0.6 microT). In total, 133 cases (14%) and 123 controls (12%) were estimated to have at least one occupation whereby magnetic field exposures exceeded 0.3 microT. Odds ratios (OR) were generated using conditional logistic regression, and were adjusted for suspected occupational risk factors for brain cancer.

RESULTS

A non-significantly increased risk of brain cancer was observed among men who had ever held a job with an average magnetic field exposure >0.6 microT relative to those with exposures <0.3 microT (OR = 1.33, 95% CI : 0.75-2.36). A more pronounced risk was observed among men diagnosed with glioblastoma multiforme (OR = 5.36, 95% CI : 1.16-24.78). Moreover, a cumulative time weighted index score of magnetic field exposure was significantly related to glioblastoma multiforme (P = 0.02). In contrast, magnetic field exposures were not associated with astrocytoma or other brain cancers.

CONCLUSIONS

Our findings support the hypothesis that occupational magnetic field exposure increases the risk of glioblastoma multiforme.