Body mass index and mortality in women: follow-up of the Canadian National Breast Screening Study cohort.

OBJECTIVE: The present study was conducted to examine the relationship between obesity and all-cause mortality in women. STUDY DESIGN AND SETTINGS: The subjects were women enrolled from 1980 to 1985 in a Canadian randomized trial, the National Breast Screening Study (NBSS) to evaluate the efficacy of mammographic screening. Mortality was ascertained by record linkage to the Canadian Mortality Data Base. Hazard ratios (HR) for the association between body mass index (BMI) and all-cause mortality were obtained from Cox proportional hazard regression models. RESULTS: During an average follow-up period of 16.5 years, 2566 deaths were identified among the 49 165 women, age 40-59 y at enrollment. The risk of all-cause death increased linearly above a BMI of 22 kg/m(2) and the trend was statistically significant. The HR (and 95% confidence intervals) in the various categories of BMI (kg/m(2)) were: BMI<18.5: 1.12 (0.99-1.25); BMI 18.5-21.9: 1.00 (reference); BMI 22-24.9: 1.15 (1.11-1.18); BMI 25.0-27.9: 1.28 (1.24-1.32); BMI 28.0 -29.9: 1.34 (1.29-1.39); BMI 30.0-34.9: 1.30 (1.25,1.35); and BMI > or =35.0: 1.40 (1.33-1.47). CONCLUSION: This study confirms the association of high BMI with increased all-cause mortality in women.

Hormone replacement therapy and endometrial cancer in Ontario, Canada.

Estrogen therapy reduces the risk of osteoporosis and cardiovascular diseases but is associated with an increased risk of endometrial cancer. We have assessed the impact of a regimen of estrogen with progestogen on risk of endometrial cancer for women 48 years and older. We conducted a case-control study in Ontario, Canada, from 1994 to 1998 by interviewing registry-based cases (n = 512) and population controls (n = 513) to obtain information on use of hormones and dietary habits. Compared to non-users, the use of opposed hormone therapy in sequential regimen for more than three years showed a borderline increase in risk (OR = 1.49, 95% CI 0.93-2. 40), but this increase was much less than among women on unopposed estrogen (OR = 4.12, 95% CI 2.21-7.71). Stronger associations were observed when duration of sequential hormone use was examined as a continuous variable (OR per three years of use = 1.21, 95% CI 1.03-1. 42). The effect of opposed hormone therapy on endometrial cancer risk appears to vary both by usage patterns and by patient characteristics of body weight and history of diabetes.

A cohort study of nutritional factors and endometrial cancer.

To evaluate the role of nutritional factors in the etiology of endometrial cancer, we performed a case-cohort analysis using data from women enrolled in the National Breast Screening Study in Canada from 1980 to 1985. For this analysis, a subcohort was constructed by selecting a 10% random sample from the 56,837 women in the dietary cohort. Cases were the 221 women diagnosed with incident adenocarcinoma of the endometrium during follow-up to December 31, 1993 and ascertained by record linkage to the Canadian Cancer Database. Information on usual diet at enrollment and other epidemiological variables was collected by means of self-administered questionnaires. Hazard ratios were obtained from proportional hazards regression models, with estimation of robust standard errors. We found a strong association of endometrial cancer with body mass index > 25 kg/m2 (hazard ratio 2.72, 95% CI: 2.06-3.50). Endometrial cancer risk was not associated significantly with intakes of total energy, carbohydrates, proteins, total fat and major fatty acids, total dietary fiber and various types of fibers, vitamin C, E and A, folic acid, beta-carotene, lutein, or cryptoxanthin. Some decrease in risk was noted with relatively high intakes of saturated fat, animal fat or lycopene. The associations observed in the study were independent of total energy intake and most non-dietary risk factors. The study suggests that dietary intakes of energy and most major nutrients are not related to the risk of endometrial cancer among Canadian women.

Alcohol and breast cancer mortality in a cohort study.

Available epidemiological evidence indicates that alcohol intake is associated with a higher risk of developing breast cancer. Plausible biological pathways include its effect on levels of estrogens, cell membrane integrity and cell-to-cell communication, inhibition of DNA repair, and congener effect. The present study evaluated the impact of alcohol on mortality from breast cancer, an area with relatively few studies in the literature. The subjects were participants in a Canadian prospective cohort study, the National Breast Screening Study (NBSS). Women were enrolled in the cohort from 1980 to 1985 to evaluate the efficacy of mammographic screening. Information on usual diet and alcohol intake at enrolment and other epidemiological variables was collected by means of a mailed, self-administered questionnaire. Mortality from breast cancer during follow- up to 31 December, 1993 was ascertained by record linkage to the Canadian Mortality Data Base maintained by Statistics Canada. During the follow-up period of 1980-1993 (average 10.3 years), 223 deaths from breast cancer were identified for this analysis. The hazard ratios for the risk of death from breast cancer increased with intakes of total alcohol of 10-20 g/day (1.039, 1.009-1.071) and > 20 g/day ( 1.063, 1.029-1.098). This increase was contributed largely by the intake of wine, a 15% increase in risk at intakes higher than 10 g/day of alcohol from wine. Alcohol from spirits was associated with a small decrease in risk of death (hazard ratio at 10g/day, 0.945, 0.915-0.976). The effect of alcohol from beer was not significant in the two categories studied. Although our results were statistically significant, the magnitude of the change in risk was small.

Plant foods, antioxidants, and prostate cancer risk: findings from case-control studies in Canada.

Epidemiological data on most cancer sites suggest that consumption of plant foods, which contain high levels of antioxidants, might slow or prevent the appearance of cancer. We used data from three case-control studies to test this hypothesis. The total study population consisted of 617 incident cases of prostate cancer and 636 population controls from Ontario, Quebec, and British Columbia. Dietary information was collected by an in-person interview with a detailed quantitative dietary history. Unconditional logistic regression analyses were performed to estimate odds ratios (ORs) and 95% confidence intervals (CIs). A decreasing, statistically significant association was found with increasing intakes of green vegetables (OR = 0.54, 95% CI = 0.40-0.71 for 4th quartile), tomatoes (OR = 0.64, 95% CI = 0.45-0.91), beans/lentils/nuts (OR = 0.69, 95% CI = 0.53-0.91), and cruciferous vegetables (OR = 0.69, 95% CI = 0.52-0.91 for 3rd quartile). Higher intakes of fruit were associated with higher ORs (OR = 1.51, 95% CI = 1.14-2.01 for 4th quartile), an effect that was seen for total fruit and citrus fruit, as well as for all other noncitrus fruits. Among the grains, refined-grain bread intake was associated with a decrease in risk (OR = 0.65 for 4th quartile), whereas whole-grain breakfast cereals were associated with a higher risk for prostate cancer. Of all the antioxidant nutrients studied, the ORs were higher with higher intakes of cryptoxanthin (OR = 1.44, 95% CI = 1.09-1.89 for 4th quartile). Exposure to certain dietary components of plant origin, which are potentially modifiable, indicates the theoretical scope for reducing the risk from prostate cancer. Future experimental studies or trials are warranted for further understanding.

Agreement of self-reported use of menopausal hormone replacement therapy with physician reports.

There have been relatively few epidemiological studies to verify the information obtained from study participants on the use of menopausal hormone replacement therapy. We conducted this study as part of a case-control study of diet, hormone use, and endometrial cancer in Toronto, Ontario, Canada, 1994-1998. We compared records from 653 subjects, 30-79 years of age, with reports from their physicians on ever/never use of hormone replacement therapy and duration, type, and dose of hormone replacement therapy. A total of 88% of the interview records were in agreement with physician reports for ever/never use of hormone replacement therapy. The overall kappa value for ever/never use agreement was 0.76 (range = 0.71-0.81), and the intraclass correlation coefficient was 0.64 (range = 0.57-0.70) for duration of hormone replacement therapy use, indicating good agreement; similar correlations were seen among cases and controls for overall use, as well as estrogen- or progestogen-alone use. Concordance for brand codes was observed for about 43% of the subjects. This study suggests that information obtained by interview in case-control studies provides a reasonable measure of ever use of hormone replacement therapy and duration of use. Interviews, however, do not represent a reliable source of information on brands and dosage of hormone replacement therapy preparations.

Alcohol and other beverage use and prostate cancer risk among Canadian men.

There are very few large scale studies that have examined the association of prostate cancer with alcohol and other beverages. This relationship was examined in a case-control study conducted in 3 geographical areas of Canada [Metropolitan Toronto (Ontario), Montreal (Quebec), and Vancouver (British Columbia)] with 617 incident cases and 637 population controls. Complete history of beverage intake was assessed by a personal interview with reference to a 1-year period prior to diagnosis or interview. In age- and energy-adjusted models for all centers combined, the odds ratio (OR) for the highest quintile of total alcohol intake was 0.89. For alcoholic beverages separately, it was 0.68 for the highest tertile of beer, 1.12 for wine and 0.86 for liquor. The decreasing trend was significant for beer intake. The results were only significant for British Columbia out of all the 3 centers studied. Whereas coffee and cola intake was not associated with prostate cancer, a decrease in risk was observed with tea intake of more than 500 g per day (OR 0.70). Our results do not support a positive association between total alcohol, coffee and prostate cancer.

A cohort study of alcohol consumption and risk of breast cancer.

The association between alcohol consumption and breast cancer risk was examined in 519 newly incident, histologically confirmed cases of breast cancer diagnosed between 1982 and 1987 within a cohort of 56,837 women enrolled in the Canadian National Breast Screening Study. These women had completed a self-administered food frequency questionnaire including alcohol consumption at enrollment into the study prior to their breast cancer diagnosis. For the total cohort, only a weak association between total alcohol consumption and breast cancer risk is observed, the adjusted relative risk for those drinking 30 or more g/day being 1.22 (95% confidence interval (CI) 0.78-1.90) compared with nondrinkers. There is some evidence for a positive association in women who were premenopausal at the time of enrollment for whom there was a monotonic increase in risk with increasing alcohol intake. Compared with nondrinkers, the adjusted relative risk for alcohol consumption of between 0 and < 10 g of alcohol daily was 1.11 (95% CI 0.71-1.71), between 10 and < 20 g was 1.37 (95% CI 0.79-2.36), between 20 and < 30 g was 1.51 (95% CI 0.80-2.86), and > or = 30 g was 1.86 (95% CI 0.96-3.66; p (trend) = 0.07). These findings contrasted with the results for postmenopausal women where there appeared to be no evidence of any relation. The association in premenopausal women is generally reasonably consistent with that of other studies that have found positive associations with alcohol intake.

Evaluation of a self-administered dietary questionnaire for use in a cohort study.

A self-administered diet questionnaire designed for use in a cohort study has been assessed in comparison with a detailed quantitative diet history previously used in and validated for case-control studies. One hundred fifty-eight women aged 40 to 59 were asked to complete the self-administered questionnaire and 123 returned it by mail. Of these women, 50 were interviewed at home using the detailed diet history. Estimates of intake of major nutrients other than fat and fatty acids are comparable from the two methods although in general, estimated intake from the self-administered questionnaire was higher than the diet history. The difference in intake of fat and fatty acids was largely but not completely accounted for by differences in amounts of added fat recorded. It is concluded that when applied to large numbers of women in a cohort study, the self-administered questionnaire is feasible to administer and will be sufficiently accurate in estimating nutrient intake as compared to estimates from a detailed, interview-type diet history.

Bladder cancer: smoking, beverages and artificial sweeteners.

A matched patient-control study of bladder cancer examined the relationship of the disease to occupation, smoking and intake of tea, coffee, cola, alcohol and artificial sweeteners.There was no association of disease with occupation for these patients. Heavy smoking gave relative risks of 6.37 and 4.36 for men and women respectively; there was evidence of a dose-response relationship. Tea and coffee intake did not increase the risk of disease nor did prolonged use of artificial sweeteners. Alcohol and cola intake increased the relative risk of bladder cancer among male smokers. There is some suggestion that smoking interacts with both alcohol and cola intake in the production of bladder cancer.