Autoimmune thyroiditis and exposure to iodine 131 in the Ukrainian cohort study of thyroid cancer and other thyroid diseases after the Chornobyl accident: results from the first screening cycle (1998-2000).

CONTEXT: Due to the Chornobyl accident, millions were exposed to radioactive isotopes of iodine and some received appreciable iodine 131 (131I) doses. A subsequent increase in thyroid cancer has been largely attributed to this exposure, but evidence concerning autoimmune thyroiditis (AIT) remains inconclusive. OBJECTIVE: The objective of the study was to quantify risk of AIT after 131I exposure. DESIGN/SETTING/PARTICIPANTS: Baseline data were collected from the first screening cycle (1998-2000) of a large cohort of radiation-exposed individuals (n = 12,240), residents of contaminated, iodine-deficient territories of Ukraine. Study individuals were under the age of 18 yr on April 26, 1986, and had thyroid radioactivity measurements made shortly after the accident. OUTCOMES: AIT was defined a priori based on various combinations of elevated antibodies to thyroid peroxidase (ATPO), TSH, and clinical findings; elevated ATPO were considered to be an indicator of thyroid autoimmunity. RESULTS: No significant association was found between 131I thyroid dose estimates and AIT, but prevalence of elevated ATPO demonstrated a modest, significant association with 131I that was well described by several concave models. This relationship was apparent in individuals with moderately elevated ATPO and euthyroid, thyroid disease-free individuals. CONCLUSIONS: Twelve to 14 yr after the Chornobyl accident, no radiation-related increase in prevalence of AIT was found in a large cohort study, the first in which 131I thyroid doses were estimated using individual radioactivity measurements. However, a dose-response relationship with ATPO prevalence raises the possibility that clinically important changes may occur over time. Thus, further follow-up and analysis of prospective data in this cohort are necessary.

Contacts with animals and humans as risk factors for adult brain tumours. An international case-control study.

While numerous studies have addressed the possible role of farming and related exposures as risk factors for brain tumours in adults, few of them have examined the potential effect of exposure to farm animals or pets. In an international multicentre case-control study, we investigated whether residence on a farm, contact with animals, or working in occupations with a high degree of potential contact with animals or humans were associated with brain tumours. Using a common questionnaire, 1177 cases of glioma, 330 with meningioma and 2478 controls from eight centres were interviewed about the exposures and, in particular, about their contacts with nine species of animals: dairy cattle, beef cattle, pigs, horses, sheep, goats, poultry, dogs and cats. Living or working on a farm was not a risk factor, for either glioma or meningioma. Except in some centres, there was no relationship between having contacts with farm animals or pets and the risk of brain tumour, for either type of tumour or either sex. In relation to seven industrial groups involving frequent human and/or animal contacts, no association was apparent for either glioma or meningioma. In relation to 25 occupational groups with potential frequent contact with humans and/or animals, for glioma there was a reduced risk for biological technicians (Odds Ratio (OR)/=0, P=0.01), and general farm workers (OR=0.66, 95% Confidence Interval (CI): 0.5-0.9). For meningioma, there was an increased risk for cooks (OR=2.0; CI: 1.2-3.4). With some exceptions, these results indicate no association between either the type of brain tumour and contacts with animals, or with occupations that include a high level of contact with animals or a high level of contact with humans.

Lactose and benign ovarian tumours in a case-control study.

We investigated the relation between benign ovarian tumours and lactose among 746 case women identified at seven New York metropolitan hospitals and 404 community controls, age and hospital frequency matched to the expected case distribution. No increase in risk was found for lactose (highest quartile versus lowest: adjusted odds ratio = 0.82 (95% CI 0.57-1.20) or for any other lactose foods.

Vegetables, fruits, legumes and prostate cancer: a multiethnic case-control study.

The evidence for a protective effect of vegetables, fruits, and legumes against prostate cancer is weak and inconsistent. We examined the relationship of these food groups and their constituent foods to prostate cancer risk in a multicenter case-control study of African-American, white, Japanese, and Chinese men. Cases (n = 1619) with histologically confirmed prostate cancer were identified through the population-based tumor registries of Hawaii, San Francisco, and Los Angeles in the United States and British Columbia and Ontario in Canada. Controls (n = 1618) were frequency-matched to cases on ethnicity, age, and region of residence of the case, in a ratio of approximately 1:1. Dietary and other information was collected by in-person home interview; a blood sample was obtained from control subjects for prostate-specific antigen determination. Odds ratios (OR) were estimated using logistic regression, adjusting for age, geographic location, education, calories, and when indicated, ethnicity. Intake of legumes (whether total legumes, soyfoods specifically, or other legumes) was inversely related to prostate cancer (OR for highest relative to lowest quintile for total legumes = 0.62; P for trend = 0.0002); results were similar when restricted to prostate-specific antigen-normal controls or to advanced cases. Intakes of yellow-orange and cruciferous vegetables were also inversely related to prostate cancer, especially for advanced cases, among whom the highest quintile OR for yellow-orange vegetables = 0.67 (P for trend = 0.01) and the highest quintile OR for cruciferous vegetables = 0.61 (P for trend = 0.006). Intake of tomatoes and of fruits was not related to risk. Findings were generally consistent across ethnic groups. These results suggest that legumes (not limited to soy products) and certain categories of vegetables may protect against prostate cancer.

Cancer mortality among males in relation to exposures assessed through a job-exposure matrix.

To identify potential associations between workplace exposures and cancer mortality risks, job titles collected from 1965 to 1971 for 58,678 men (a subset of a large representative sample of the Canadian workforce) were transformed into probable chemical exposures using a job-exposure matrix developed in Montreal. Mortality follow-up was determined through computerized record linkage with the National Mortality Database in Canada for 1965-1991. Cancer mortality risk was evaluated at two levels of exposure, any and substantial, using Poisson regression controlling for age, calendar period, and social class. Among the 58,678 men, 3,160 died of cancer. Using a liberal reporting criterion, relative risk (RR) >1.0, five or more exposed cancer deaths, p < or = 0.100, several potential associations were identified, including: lung cancer and any exposure to abrasives dust (RR = 2.84), prostate cancer and any exposure to calcium carbonate (RR = 2.46), and prostate cancer and substantial exposure to metallic dust (RR = 2.13).

Alcohol consumption and risk of breast cancer: a cohort study.

OBJECTIVES: To study the association between alcohol consumption and breast cancer risk. METHODS: A case-cohort analysis was undertaken within the cohort of 56,837 women who were enrolled in the Canadian National Breast Screening Study (NBSS) and who completed a self-administered dietary questionnaire. (The NBSS is a randomized controlled trial of screening for breast cancer in women aged 40-59 at recruitment.) The cohort was recruited between 1980 and 1985, and during follow-up to the end of 1993 a total of 1469 women in the dietary cohort were diagnosed with biopsy-confirmed incident breast cancer. For comparative purposes a subcohort consisting of a random sample of 5681 women was selected from the full dietary cohort. After exclusions for various reasons the analyses were based on 1336 cases and 5238 noncases. RESULTS: When compared to nondrinkers the adjusted incidence rate ratios (95% confidence intervals) for those consuming > 0 and < or = 10 g of alcohol/day, > 10 and < or = 20 g/day, > 20 and < or = 30 g/day, > 30 and < or = 40 g/day, > 40 and < or = 50 g/day, and > 50 g/day were 1.01 (0.84-1.22), 1.16 (0.91-1.47), 1.27 (0.91-1.78), 0.77 (0.51-1.16), 1.00 (0.57-1.75), and 1.70 (0.97-2.98), respectively; the associated p value for the test for trend was 0.351. Similar findings were obtained when analyses were conducted separately in the screened and control arms of the NBSS, in premenopausal and postmenopausal women, for screen-detected and interval-detected breast cancer, and by levels of other breast cancer risk factors. CONCLUSIONS: The results of this study suggest that alcohol consumption might be associated with increased risk of breast cancer at relatively high levels of intake.

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.

Premorbid diet in relation to survival from prostate cancer (Canada).

OBJECTIVES: To examine the associations between prediagnostic energy, fat, and vitamin A intake and survival from prostate cancer. METHODS: Two hundred and seven cases of prostate cancer from Toronto and 201 cases from Vancouver provided diet histories at diagnosis between 1989 and 1992 and were followed for survival from prostate cancer. After exclusions for various reasons, 263 cases (135 from Toronto, 128 from Vancouver) were analyzed in Cox proportional hazards models. RESULTS: Following adjustments for clinical stage, histologic grade, and other factors, significantly lower risks of dying from prostate cancer in the highest compared with the lowest tertiles of monounsaturated fat intakes were observed in each city and in the combined city analyses (combined cities: hazard ratio [HR] = 0.3; 95% confidence interval (CI) = 0.1-0.7). Survival from prostate cancer was significantly better for cases in the highest tertile of energy intake in Toronto (HR = 0.1; CI = 0.01-0.6) in contrast to that in Vancouver where these cases did relatively worse (HR = 2.6; CI = 0.6-10.7). Other nutrients were either not consistently or not significantly associated with prostate cancer survival in the two cities. CONCLUSIONS: This bi-center cohort study observed a consistent and significant inverse association between the premorbid intake of monounsaturated fat and risk of death from prostate cancer. The inconsistent results for energy intake between cities could potentially be attributed to non-respondent bias in Toronto.

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.

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.

Surveillance of potential associations between occupations and causes of death in Canada, 1965-91.

OBJECTIVE: To detect unsuspected associations between workplace situations and specific causes of death in Canada. METHODS: An occupational surveillance system was established consisting of a cohort of 457,224 men and 242,196 women employed between 1965 and 1971, constituting about 10% of the labour force in Canada at that time. Mortality between 1965 and 1991 has been determined by computerised record linkage with the Canadian mortality database. Through regression analysis, associations between 670 occupations and 70 specific causes of death were measured. RESULTS: There were almost 116,000 deaths among men and over 26,800 deaths among women. About 28,000 comparisons were made between occupations and specific causes of death. With various reporting criteria, several potential associations were highlighted, including: infectious disease mortality among barbers and hairdressers; laryngeal cancer among male metal fitters and assemblers; lung cancer among female waiters; breast cancer among female metal fitters and assemblers; brain cancer among female nursing assistants and male painters; and ischaemic heart disease among female inspectors and foremen and among male taxi drivers and chauffeurs. CONCLUSIONS: When excess risk of mortality is apparent, the intention of this occupational surveillance system is to spark further studies to gain aetiological knowledge.

Role of medical history in brain tumour development. Results from the international adult brain tumour study.

In an international population-based case-control study carried out in 8 centres in 6 countries, we investigated the role of specific medical conditions in the aetiology of brain tumours in adults. Recruited were 1,178 glioma and 331 meningioma cases and 2,493 age- and gender-matched population controls. Only medical conditions occurring at least 2 years before brain tumour diagnosis were considered. Relative risks (RRs) and 95% confidence intervals (CIs) were estimated using a conditional logistic regression model. Heterogeneity between centres was tested. No association between meningioma and previous medical conditions was observed. For glioma, there was an increased risk associated with epilepsy (RR = 6.55, 95% CI 3.40-12.63), but this was considerably weaker for epilepsy of more than 20 years duration. The risk remained elevated after adjustment for use of anti-epileptic drugs. There was a statistically significant inverse association between glioma and all allergic diseases combined (RR = 0.59, 95% CI 0.49-0.71); this was also observed for specific allergic conditions, namely, asthma and eczema. Subjects who reported a history of infectious diseases (e.g., colds, flu) showed a 30% reduction in risk (RR = 0.72, 95% CI 0.61-0.85). The decreased risks for glioma in subjects reporting a history of allergic conditions or infectious diseases may indicate an influence of immunological factors on the development of glioma. The association between glioma and epilepsy has to be interpreted cautiously and needs further investigation.

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.

An international case-control study of adult glioma and meningioma: the role of head trauma.

BACKGROUND: Increased brain tumour risk after head trauma suggested by case reports and clinical series has been previously studied epidemiologically with mixed results. An international multicentre case-control study investigated the role of head trauma from injury or sports participation in adult brain tumour risk. METHODS: In all, 1178 glioma and 330 meningioma cases were individually or frequency matched to 2236 controls. Only exposures that occurred at least 5 years before diagnosis and head injuries that received medical attention were considered. RESULTS: Risk for ever having experienced a head injury was highest for male meningiomas (odds ratio [OR] = 1.5, 95% confidence interval [CI] : 0.9-2.6) but was lower for 'serious' injuries, i.e. those causing loss of consciousness, loss of memory or hospitalization (OR = 1.2, 95% CI: 0.6-2.3). Among male meningiomas, latency of 15 to 24 years significantly increased risk (OR = 5.4, 95% CI: 1.7-16.6), and risk was elevated among those who participated in sports most correlated with head injury (OR = 1.9, 95% CI: 0.7-5.3). Odds ratios were lower for male gliomas (OR = 1.2, 95% CI : 0.9-1.5 for any injury; OR = 1.1, 95% CI: 0.7-1.6 for serious injuries) and in females in general. CONCLUSIONS: Evidence for elevated brain tumour risk after head trauma was strongest for meningiomas in men. Findings related to sports should be interpreted cautiously due to cultural variability in our data and our lack of complete data on physical exercise in general which appeared to be protective.