Surveillance & Risk Assessment, Centre for Chronic Disease Prevention and Control, Population and Public Health Branch, Health Canada, Tunney's Pasture AL0601C1, Ottawa, Ontario K1A 0L2, Canada. Yang_Mao@hc-sc.gc.ca
This study assessed the influence of active and passive smoking on the risk of stomach cancer by subsite. Mailed questionnaires were used to obtain information on 1171 newly diagnosed histologically confirmed stomach cancer cases and 2207 population controls between 1994 and 1997 in eight Canadian provinces. Data were collected on socio-economic status, lifestyle and passive smoking status. Odds ratios (OR) and 95% confidence intervals (95% CI) were derived by logistic regression. Compared with those who had never smoked, there was strongly increased risk for ex- and current smokers among subjects with cardial stomach cancer. For men with cardial cancer, the adjusted ORs were 1.9 (95% CI 1.2-3.0) and 2.6 (95% CI 1.6-4.3) for ex-smokers and current smokers, respectively, with a similar pattern among women. Among men, the adjusted ORs were lower for subsites of stomach cancer other than cardia. These findings suggest that active and passive smoking may play an important role in the development of cardial stomach cancer.
Alcohol, tobacco and coffee consumption and the risk of pancreatic cancer: results from the Canadian Enhanced Surveillance System case-control project. Canadian Cancer Registries Epidemiology Research Group.
The relationship between alcohol, tobacco and coffee consumption and pancreatic cancer was investigated using population-based case-control data obtained from eight Canadian provinces. Our findings are based on analyses performed on 583 histologically confirmed pancreatic cancer cases and 4813 controls. Questionnaire data were obtained directly from 76% of the cases. Male subjects with 35 or more cigarette pack-years had an increased risk of developing pancreatic cancer relative to never smokers (OR= 1.46, 95% CI 1.00-2.14). Similarly, women reporting at least 23 cigarette pack-years of smoking had an odds ratio of 1.84 (95% CI 1.25-2.69). For the most part, consumption of total alcohol, wine, liquor and beer was not associated with pancreatic cancer. Coffee drinking was not related to pancreatic cancer. More work is needed to clarify the role of these and other potentially modifiable risk factors as a means to reduce the incidence of this disease for which treatment results remain disappointing.
To examine the pattern of testicular cancer incidence by age, time period and birth cohort since 1969 in Canada.
In addition to analyses of the secular trends by age group and birth cohort separately, an age-period-cohort model and the submodels with standard Poisson assumptions were fitted to the data.
The overall age-adjusted incidence of testicular cancer increased in Canada, from 2.8 per 100,000 males in 1969-71 to 4.2 in 1991-93. The younger age groups showed much higher absolute incidence rates in the recent period compared with those in the early period. Age-period-cohort modelling of data restricted to males aged 20-84 years suggested that the observed increase in testicular cancer could be largely attributed to a birth cohort effect. A steady increase in risk was observed among men born since 1945; those born between 1959 and 1968 were 2.0 (95% CI, 1.5-2.6) times as likely to develop testicular cancer as those born between 1904 and 1913.
The risk of testicular cancer has increased over time and changing exposure to environmental factors early in life may be responsible for this.
A cohort study of the mortality experience (1971-1987) of male Canadian prairie farmers has been conducted. This involved linking the records of 156,242 male Alberta, Saskatchewan and Manitoba farmers identified on the 1971 Census of Agriculture and the corresponding Census of Population to mortality records. Exposure indices for individual farm operators were derived from 1971 Census of Agriculture records. Cancer histologies for brain cancer cases were obtained from the Canadian National Cancer Incidence Database and from Provincial Cancer Registries. A statistically significant association was noted between risk of dying of glioblastomas and increasing fuel/oil expenditures (test for trend p = 0.03, top quartile relative risk = 2.11, 95% confidence interval = 0.89-5.01). No significant association was found between brain cancer and either education or mother tongue. However, low income was associated with a significantly reduced risk of brain cancer mortality.
A number of studies have observed increased cancer incidence rates among individuals who have received renal transplants. Generally, however, these studies have been limited by relatively small sample sizes, short follow-up intervals or focused on only one cancer site. We conducted a nationwide population-based study of 11,155 patients who underwent kidney transplantation between 1981 and 1998. Incident cancers were identified up to December 31, 1999, through record linkage to the Canadian Cancer Registry. Patterns of cancer incidence in the cohort were compared to the Canadian general population using standardized incidence ratios (SIRs). We examined variations in risk according time since transplantation, year of transplantation and age at transplantation. In our patient population, we observed a total of 778 incident cancers versus 313.2 expected (SIR = 2.5, 95% CI = 2.3-2.7). Site-specific SIRs were highest for cancer of the lip (SIR = 31.3, 95% CI = 23.5-40.8), non-Hodgkin's lymphoma (NHL) (SIR = 8.8, 95% CI = 7.4-10.5), and kidney cancer (SIR = 7.3, 95% CI = 5.7-9.2). SIRs for NHL and cancer of the lip and kidney were highest and among transplant patients. This study confirms previous findings of increased risks of posttransplant cancer. Our findings underscore the need for increased vigilance among kidney transplant recipients for cancers at sites where there are no population-based screening programs in place.
A cohort study of the mortality experience (1950-1984) of 1,772 Newfoundland underground fluorspar miners occupationally exposed to high levels of radon daughters (mean dose = 382.8 working levels months) has been conducted. Observed numbers of cancers of the lung, salivary gland, and buccal cavity and pharynx were significantly elevated among these miners. A highly significant relation was noted between radon daughter exposure and risk of dying of lung cancer; the small numbers of salivary gland (n = 2) and buccal cavity and pharynx (n = 6) cancers precluded meaningful analysis of dose response. Attributable and relative risk coefficients for lung cancer were estimated as 6.3 deaths per working level month per million person-years and 0.9% per working level month, respectively. Relative risk coefficients were highest for those first exposed before age 20 years. Cigarette smokers had relative and attributable risk coefficients comparable to those of nonsmokers. Relative risks fell sharply with age, whereas attributable risks were lowest in the youngest and oldest age groups. The results suggest that efforts to raise existing occupational exposure standards may be inappropriate.
Large declines have occurred in cardiovascular disease mortality in both sexes in Canada during the past two decades. However, there are many countries with substantially lower rates at the present time. Ischemic heart disease mortality accounts for about 60% of cardiovascular disease mortality. Cardiovascular disease rates have declined progressively since the mid-1960s in males 35 to 64 and 65 or more years of age, as well as in females in the latter age group. In younger females, 35 to 64 years of age, a slowly progressive reduction in rates started as early as 1930. Trends for stroke mortality also reveal similar long term reductions in rates since 1930 in both sexes. Relative risks for smoking, hypertension, elevated serum cholesterol and diabetes were analyzed. Almost one-third of the cardiovascular deaths in males were attributable to smoking. Population attributable risks for the four risk factors together were 53% for both sexes. Attention is drawn to the increased risks for persons in lower socioeconomic groups and those with low standards of education and the importance of recognition of these factors in intervention programs.
Recently published evidence indicates that involuntary smoking causes an increased risk of lung cancer among nonsmokers. Information was compiled on the proportion of people who had never smoked among victims of lung cancer, the risk of lung cancer for nonsmokers married to smokers and the prevalence of such exposure. On the basis of these data we estimate that 50 to 60 of the deaths from lung cancer in Canada in 1985 among people who had never smoked were caused by spousal smoking; about 90% occurred in women. The total number of deaths from lung cancer attributable to exposure to tobacco smoke from spouses and other sources (mainly the workplace) was derived by applying estimated age- and sex-specific rates of death from lung cancer attributable to such exposure to the population of Canadians who have never smoked; about 330 deaths from lung cancer annually are attributable to such exposure.
The effects of residential exposure to environmental tobacco smoke were studied in a sample of 6,529 Canadian children under 15 years of age. Univariate analysis indicated an elevated risk of bronchitis among children whose mothers were single, or under age 25, or whose income or educational level was low. Multivariate analysis indicated that the relative risk of bronchitis among children whose mothers were current smokers relative to those whose mothers never smoked was 3.0 (95% CI:1.6,5.2). Significant dose-response relationships between risk of bronchitis and amount smoked as well as duration of exposure were observed. Using the composite exposure score of all smokers in the household as the source of exposure, the risk of bronchitis decreased slightly but remained significantly elevated. Examination of the risk conferred by the mother's smoking relative to the total household exposure showed that most of the elevation in risk was associated with the mother's smoking contribution. Asthma was also studied, but failed to show a statistically significant association with smoking.