Kenneth C. Johnson

Risk factors for prostate cancer: results from the Canadian National Enhanced Cancer Surveillance System

Objectives: To evaluate the relationship between prostate cancer and several potential lifestyle risk factors.Methods: We analyzed 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 1623 histologically confirmed prostate cancer cases and 1623 male controls aged 50–74.Results: Cases were more likely to have a first-degree relative with a history of cancer, particularly prostate cancer (OR = 3.1, 95% CI = 1.8–5.4). Reduced risks of prostate cancer were observed among those of Indian descent (OR = 0.2, 95% CI = 0.1–0.5) or any Asian descent (OR = 0.3, 95% CI = 0.2–0.6) relative to those of western European descent. Total fat consumption, tomato and energy intake, were not associated with prostate cancer. The risk of prostate cancer was inversely related to the number of cigarettes smoked daily (p = 0.06) and cigarette pack-years (p < 0.01), while no association was observed between the total number of smoking years or the number of years since smoking cessation. Anthropometric measures and moderate and strenuous levels of leisure time physical activity were not strongly related to prostate cancer. In contrast, strenuous occupational activities at younger ages appeared protective.Conclusions: Our analyses are limited by the absence of data related to tumor severity and screening history. Further studies are needed to investigate the relationship between behavioral risk factors and prostate cancer screening practices.

Physical activity, anthropometric factors and risk of pancreatic cancer: Results from the Canadian enhanced cancer surveillance system

To explore the hypothesis that insulin resistance may be an etiologic factor in pancreatic cancer, we assessed the pancreatic cancer risk associated with anthropometric factors and physical activity, both of which are important determinants of insulin sensitivity in humans. Three hundred and twelve patients with histologically confirmed pancreatic cancer were compared to 2,919 controls in a population‐based, case‐control study in 7 of the 10 Canadian provinces. Participants were asked to report their exposure status for the period 2 years before interview. Men in the highest quartile of body mass index (BMI, ≥28.3 kg/m2) were at increased risk of pancreatic cancer [adjusted odds ratio (OR) = 1.90, 95% confidence interval (CI) 1.08–3.35]. In addition, men who reported a decrease in weight of at least 2.9% from their lifetime maximum were at reduced risk compared to those reporting a ≤2.9% loss (≥10.2% loss, OR = 0.51, 95% CI 0.30–0.86). BMI 2 years before interview was not associated with pancreatic cancer risk among women, though those reporting a ≥12.5% decrease in weight from their lifetime maximum had substantially lower risk compared to those in the baseline quartile (OR = 0.53, 95% CI 0.29–0.99). After adjustment for age, province of residence, dietary intake and anthropometric factors, men in the highest quartile of the composite moderate and strenuous physical activity index were at reduced risk of pancreatic cancer (OR = 0.53, 95% CI 0.31–0.90). Physical activity did not appear to be associated with pancreatic cancer among women, though a tendency for reduced risk with increasing levels of strenuous activity was suggested (p for trend = 0.06). Our findings support the hypothesis that insulin resistance is an etiologic factor in the development of pancreatic neoplasms among men and possibly women.

Lifetime residential and workplace exposure to environmental tobacco smoke and lung cancer in never‐smoking women, Canada 1994–97

Although the risk of lung cancer among never‐smokers living with a spouse who smokes has been extensively studied, the impact of lifetime residential and workplace environmental tobacco smoke has received less attention. As part of a large population‐based case‐control study of lung cancer, we collected lifetime residential and occupational passive smoking information from 71 women with lung cancer and 761 healthy control subjects, all of whom reported being lifetime nonsmokers. The adjusted odds ratio (OR) for lung cancer associated with residential passive exposure only was 1.21 (95% confidence interval [CI] 0.5–2.8). Although more years of and more intense residential passive smoke exposure tended to be associated with higher risk estimates, no clear dose‐response relationship was evident. The OR for women with passive exposure as a child and as an adult was 1.63 (95% CI 0.8–3.5) and for those only exposed as an adult 1.20 (95%CI 0.5–3.0). Exposure to environmental tobacco smoke only in the workplace was associated with an adjusted OR of 1.27 (95% CI 0.4–4.0). Risks associated with increasing occupational exposure year tertiles were 1.24, 1.71 and 1.71. Total smoker‐years of residential and occupational exposure combined resulted in a statistically significant trend (linear test for trend p = 0.05) with ORs for tertiles of exposure of 0.83, 1.54 and 1.82. Our results are consistent with the literature suggesting that long‐term, regular exposure to either residential or occupational environmental tobacco smoke is associated with increased lung cancer risk in never‐smoking women.

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/m2) 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/m2 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.

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-Hodgkins 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.

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.

Effects on Subject Response of Information Brochures and Small Cash Incentives in a Mail-Based Case-Control Study

PURPOSEnTo investigate the impact on subject response of an information brochure and cash incentives included with mailed questionnaires in case-control studies.nnnMETHODSnA randomized trial was carried out within a case-control study investigating cancer in the Province of Ontario. Brochures were included with half of the mailed questionnaires sent to 7487 cases and 2561 controls. Controls were also sent cash incentives of

Association of Obesity and Cancer Risk in Canada

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

5, or no money.nnnRESULTSnWith the brochure, response changed from 75.0% to 75.8% in cases, and from 70.3% to 71.1% in controls. Adjusting for differences in age, residence, sex, and cancer site/status, the change was 0.2% [95% confidence interval (CI) = -1.7-2.1] in cases, and 0.6% (95% CI = -3.1-4.3) in controls. The

Dietary Intake of Lycopene Is Associated with Reduced Pancreatic Cancer Risk

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