Trends in childhood injury mortality in Canada, 1979-2002.

OBJECTIVE: To examine national trends in mortality rates for injuries among Canadian children younger than 15 years in 1979-2002. METHODS: Data on injury deaths were obtained from the Canadian Vital Statistics system at Statistics Canada. Injuries were classified using the codes for external cause of injury and poisoning (E-codes) by intent and by mechanism. Mortality rates were age adjusted to the 1990 world standard population. Negative binomial regression was used to estimate the secular trends. RESULTS: Annual mortality rates for total and unintentional injuries declined substantially (from 23.8 and 21.7 in 1979 to 7.2 and 5.8 in 2002, respectively), whereas suicide deaths among children aged 10-14 showed an increasing trend. All Canadian provinces and territories showed a decreasing trend in mortality rates of total injuries. Motor vehicle related injuries were the most common cause of injury deaths (accounted for an average of 36.4% of total injury deaths), followed by suffocation (14.3%), drowning (13.5%), and burning (11.1%); however, suffocation was the leading cause for infants. The number of potential years of life lost due to injury before age 75 decreased from 89 343 in 1979 to 27 948 in 2002 for children aged 0-14 years. CONCLUSIONS: During the period 1979-2002, there were dramatic decreases in childhood mortality for total injuries and unintentional injuries as well as various degrees of reduction for all causes of injury except suffocation in children aged 10-14 years and drowning in infants. The reason for the reduction in injury mortality might be multifactoral.

Survival patterns for the top four cancers in Canada: the effects of age, region and period.

This study examined the variations in survival rates (1989-1991) and the trends (1969-1991), by sex, age and province, for patients diagnosed with breast, colorectal, lung or prostate cancer in Canada and compared the Canadian rates with those of nine American SEER registries. Five-year age-standardized relative survival rates (ASRs) were calculated, and the trends were estimated from variance-weighted linear regression of the ASRs for five periods of diagnosis (1969-1973, 1974-1978, 1979-1983, 1984-1988 and 1989-1991). In 1989-1991, the ASR varied among provinces for each cancer except female colorectal cancer. The lowest survival rates were observed in the youngest patients (15-44) for breast and prostate cancers, and in the oldest patients (75-99) of both sexes for lung and colorectal cancers. Over the five periods, a major trend toward improved survival was observed for breast, prostate and colorectal cancers (P<0.008), whereas no changes were seen for lung cancer. The ASRs in the western region were higher than in the Atlantic region over time (P<0.02) for each cancer. From the third period onward, the ASRs for Canadian patients with lung cancer were similar to those for the US patients and lower than for Canadian patients with breast, prostate or colorectal cancer. The observed increases in ASR for breast and prostate cancer are likely due to the increased use of screenings and the improved treatment modalities.

Survival of women with breast cancer in Ottawa, Canada: variation with age, stage, histology, grade and treatment.

This study examined the 5-year survival of 2192 breast cancer women diagnosed between 1994 and 1997 in Ottawa, Canada, by age, TNM stage, histology, grade and treatment, including assessment of the independent value of variables in defining prognosis. Our results showed that age, stage, treatment and grade significantly influenced outcome regardless of the confounding factors considered, with histology failing to achieve significant independent prognostic information. The survival rates were highest at ages 50-69 years for stage I and at ages 40-49 years for stages II-IV. The rates were lowest at ages or=70 years for stages III-IV. The differences in survival between grade 1 and grade 3 were 9% in stage I and 20% in stage II. The treatment leading to the best survival was surgery plus radiation for stages I-II and surgery combined with chemotherapy for stages III-IV. Lobular carcinoma had a better prognosis than ductal carcinoma; this can be explained by more grade 1 and less grade 3 cases in lobular carcinoma. The worse prognosis for young patients than other ages can be explained by their higher proportion of poorly differentiated cancers. Stage I patients aged 50-69 years having the best survival is likely due to the earlier diagnosis achieved through screening.

Increasing thyroid cancer incidence in Canada, 1970-1996: time trends and age-period-cohort effects.

We examined time trends in thyroid cancer incidence in Canada by age, time period and birth cohort between 1970 and 1996. Age-specific incidence rates by time period and birth cohort were calculated and age-period-cohort modelling used to estimate effects underlying the observed trends. Overall age-adjusted incidence rates of thyroid cancer doubled, from 3.3 and 1.1 per 100 000 in 1970-72 to 6.8 and 2.2 per 100 000 in 1994-96, among females and males respectively. Almost all the increase between 1970-72 and 1994-96 was due to papillary carcinoma of the thyroid. Age, birth cohort and period effects significantly improved the fit of the model for females, while age and birth cohort effects were significant determinants of the incidence among males. There were significant differences in the patterns/curvature for age, period and birth cohort effects between women and men. Our results suggest that the increases in thyroid cancer incidence in Canada may be associated with more intensive diagnostic activities and change in radiation exposure in childhood and adolescence. Temporal changes in reproductive factors among young women may explain some of the gender differences observed.

Socioeconomic status and lung cancer risk in Canada.

BACKGROUND: Several epidemiological studies have found that lung cancer is inversely related to socioeconomic status (SES) and suggest it as a possible risk factor for lung cancer. This study examines SES and lung cancer risk in Canada. METHODS: Mailed questionnaires with telephone follow-up were used to obtain data on 3280 newly diagnosed, histologically confirmed lung cancer cases and 5073 population controls, between 1994 and 1997, in eight Canadian provinces. Measurement included information on SES, smoking habits, alcohol use, diet, residential and occupational histories and both residential and occupational exposure to environmental tobacco smoke (ETS). Odds ratios (OR) and 95% CI were derived from unconditional logistic regression analysis. RESULTS: Compared with high income adequacy, an increased risk was found among low income males and females, with adjusted OR of 1.7 (95% CI : 1.3-2.2) and 1.5 (95% CI : 1.1-2.0), respectively. Compared with < or = 8 years of education, the adjusted OR were 0.6 (95% CI : 0.5-0.7) and 0.6 (95% CI : 0.5-0.8) for > or = 14 years education among males and females, respectively. Lung cancer risk was significantly increased for males of some social classes. The population attributable risk for income adequacy, education and social class was 24%, 25% and 21% among males, respectively, and 14% and 19% for income adequacy and education among females, respectively, in this Canadian population. CONCLUSIONS: A statistically significant association between income adequacy, education social class and lung cancer risk was found.

Non-Hodgkin's lymphoma and occupational exposure to chemicals in Canada. Canadian Cancer Registries Epidemiology Research Group.

BACKGROUND: The incidence of non-Hodgkin's lymphoma (NHL) has been increasing in Canada. This study assessed the effect of occupational exposure to specific chemicals on the risk of NHL. PATIENTS AND METHODS: Mailed questionnaires were used to obtain data on 1469 newly diagnosed, histologically confirmed NHL cases and 5073 population controls between 1994 and 1997 in eight Canadian provinces. Data was collected on socioeconomic status, life-style, diet, occupation, and years of exposure to any of 17 chemicals. Odds ratios (OR) and 95% confidence intervals (95% CI) were derived by logistic regression. RESULTS: The study found an increased risk of NHL among males exposed to benzidine, mineral, cutting, or lubricating oil, pesticides, and herbicides. Compared with non-exposure to each specific chemical, the adjusted ORs were 1.9 (95% CI: 1.1-3.4) for benzidine, 1.3 (95% CI: 1.0-1.5) for mineral, cutting, or lubricating oil, 1.3 (95% CI: 1.0-1.6) for herbicides, and 1.3 (95% CI: 1.0-1.6) for pesticides. Excess risk of NHL among females was associated with exposure to pesticides and wood dust. ORs increased with increasing exposure in years to benzidine and herbicides for males and with increasing exposure years to wood dust for females. These trends were statistically significant (P < 0.05). CONCLUSIONS: The findings in this study suggest that occupational exposure to specific chemicals plays an important role in the development of NHL in Canada.

Is occupation a risk factor for thyroid cancer? Canadian Cancer Registries Epidemiology Research Group.

A Canadian case-control study explored the etiology of thyroid cancer, including occupational exposure. Analysis of job history from 1272 thyroid cancer patients and 2666 controls revealed statistically significant risks among the following occupations: Wood Processing, Pulp and Papermaking (odds ratio [OR] = 2.54, 95% confidence interval [CI] = 1.11-5.83); Sales and Service (OR = 1.26, 95% CI = 1.05-1.52); and Clerical (OR = 0.81, 95% CI = 0.67-0.97). ORs were adjusted for age, sex, province, cigarette smoking, education, self-reported exposure to radiation at work, and duration of employment. Exposure to ionizing radiation or electromagnetic fields at work (inferred from job histories) did not affect risk, nor did socioeconomic status, measured by education, income, or occupational prestige. Possible explanations for the results and further investigations are discussed.

Parental cigarette smoking, hard liquor consumption and the risk of childhood brain tumors--a case-control study in northeast China.

In this study we examine the effect of parents' lifestyles on the risk of childhood brain tumors. Parents of 82 children newly diagnosed with primary malignant brain tumors and 246 individually matched hospital controls were interviewed in the hospital wards between September 1991 and December 1996. Data were collected on socioeconomic status, parental lifestyle prior to and during the pregnancy, and family history. Odds ratios and 95% confidence intervals were derived through conditional logistic regression. The risk of childhood brain tumors was associated with paternal use of hard liquor prior to the pregnancy: the odds ratios were 3.72 (95% CI = 1.91-7.26) for < or = 15 years of hard liquor consumption and 4.06 (95% CI = 1.09-15.21) for > or = 16 years of hard liquor consumption compared with never consuming hard liquor (test for trend p = 0.0001); the odds ratios increased with increasing lifetime hard liquor consumption. There is little evidence to support an association between childhood brain tumors and parents' smoking prior to or during pregnancy.

Ovarian cancer histology-specific incidence trends in Canada 1969-1993: age-period-cohort analyses.

This study examined histology-specific incidence trends of ovarian cancer in Canada, 1969-1993. The impact of age, period and cohort effects on these trends were studied by means of age-period-cohort analysis. Age-standardized incidence rates of serous, endometrioid, clear cell and germ cell tumours increased significantly and the rates of sex cord-stromal and other classified epithelial ovarian tumours decreased considerably. The rates of mucinous and NOS/unclassified tumours remained unchanged. Cohort effect has a major impact on incidence trends of serous, endometrioid, germ cell, sex cord-stromal and other classified epithelial ovarian tumours but no meaningful impact on trends of mucinous, clear cell, or NOS/unclassified ovarian tumours. Various cohort patterns by histology subtypes were observed: the risk of developing serious tumours increased markedly among birth cohorts of 1895-1930, stabilized thereafter and decreased among young cohorts of 1950-1960; the risk of germ cell tumours increased significantly among young cohorts of 1965-1980; and the risk of sex cord-stromal tumours dropped constantly among cohorts 1910-1950. Various period patterns by histology subtypes observed in this study suggested changes in histology classification criteria over the period. Further studies need to consider the various etiologies and the classification criteria changes according to histology subtypes.

Regionalized delivery and variable utilization of coronary artery bypass grafting in Ontario from 1981 to 1991.

OBJECTIVE: To analyse the geographic variation in the rates of coronary artery bypass grafting (CABG) between 1981 and 1991. DESIGN: Retrospective study of discharge abstracts (from the provincial hospital discharge database) for odd fiscal years. SETTING: Ontario. PARTICIPANTS: All Ontario residents undergoing CABG between 1981 and 1991. OUTCOME MEASURES: Age- and sex-standardized median, maximum and minimum (plus 25th and 75th percentile) rates of CABG per 100,000 population aged 20 years and over, as well as interregional variation. RESULTS: The median rate of CABG rose from 46.2 to 72.7 per 100,000 adults between 1981 and 1991. The minimum rate varied from 1.9 to 12.4 per 100,000 and the maximum rate from 110.4 to 172.1 per 100,000 during the study period. Variations in the area-specific rates were significant in all years (p < 0.0001, based on the likelihood ratio chi 2 test after adjustment for age and sex). None of the four summary statistical measures showed any obvious diminution between 1981 and 1989, nor was there a change in the utilization pattern during the waiting-list crisis years of 1987 and 1989. However, the summary measures did reach their lowest level in 1991. The relative consistency of local practice patterns was tested by means of ranking area-specific rates and comparing the rankings for different years. Correlation coefficients varied from 0.50 to 0.82 (p < 0.0001); the correlation coefficient for 1991 on 1981 was 0.61 (p < 0.0001). CONCLUSIONS: Consistent and marked variations in the use of CABG existed across the counties of Ontario from 1981 to 1991. Despite a major expansion in provincial caseload capacity and planned regionalization of CABG as a surgical service, incremental resources were apparently not allocated in a manner that reduced interregional discrepancies.

Alterations in fatty acid metabolism in adriamycin cardiomyopathy.

Myocardial fatty acid metabolism may be impaired in adriamycin cardiomyopathy. In order to determine the extent of fatty acid metabolism alterations, we measured steady state [14C]palmitate oxidation and the incorporation of [14C]palmitate into the neutral lipid pool in a rat model of adriamycin cardiomyopathy. Isolated hearts from control rats and rats treated with adriamycin were perfused with 1.2 mmol/l of [14C]palmitate for 30 min to achieve steady state oxidation measured as [14C]O2 production; then perfused with 1.2 nmol/l of unlabelled palmitate. Hearts were killed early (0-5 min) or late (10-30 min) after the [14C]palmitate perfusion, to determine incorporation into the neutral lipid pool, and neutral lipid utilization. In the control group steady state oxidation was reached in 10 min ([14C]O2 production = 580 +/- 61 nmol/min/g dry wt) of perfusion. In the adriamycin treated group, mean CO2 production was significantly reduced at 10 min (329 +/- 44 nmol/min/g dry wt, P < 0.01 v control). At 30 min, [14C]O2 production in the treated group was not significantly different than controls (521 +/- 65 nmol/min/g dry wt v 617 +/- 36 nmol/min/g dry wt, P = N.S.). The incorporation of [14C]palmitate into the neutral lipid pool measured in the early subgroup was significantly reduced for adriamycin treated hearts v controls (7.2 +/- 0.6 v 12.0 +/- 1.4 mumol/g dry wt respectively, P < 0.01). In the control group 14C labelled neutral lipid reduced with time to 8.4 +/- 1.1 mumol/g dry wt (P < 0.05) in the late group. The adriamycin group demonstrated no significant change between early and late measurements. In conclusion, in adriamycin cardiomyopathy: (1) there is significant delay in achieving steady state palmitate oxidation, although the steady state rate is near normal; (2) palmitate incorporation into the neutral lipid pool is reduced; (3) neutral lipid pool utilization may also be reduced. These data suggest impaired uptake of palmitate into the cell in adriamycin cardiomyopathy, with a relatively maintained capacity for oxidative metabolism.

Trends in coronary artery bypass grafting in Ontario from 1981 to 1989.

OBJECTIVES: To determine the trends in overall and age-specific rates of coronary artery bypass grafting (CABG) in Ontario from 1981 to 1989 and to assess whether relative resource scarcity, as manifested in waiting lists, resulted in obvious age-related or sex-related changes in utilization. DESIGN: Computerized compilation of hospital discharge abstracts from the Hospital Medical Records Institute. All separations for every other year from Apr. 1, 1981, to Mar. 31, 1990, were included. Procedures rather than patients were the unit of analysis (repeat procedures were double-counted if associated with separate hospital admissions). SETTING: Ontario acute care hospitals offering CABG. PATIENTS: People aged 20 years and over who underwent one or more CABG procedures. RESULTS: The overall rate of CABG increased by 31% in the study period, plateauing only between 1983 and 1985. By 1989-90 the rate was 66.03 per 100,000. The highest annual increase in the rate was among people aged 65 to 74 years, at 17.61 procedures per 100,000, as compared with 4.64 per 100,000 among people 75 years and over. In 1989-90 those aged 65 and over represented 37% of the total caseload. The overall male:female ratio did not change significantly throughout the study period. CONCLUSIONS: Since the CABG utilization rate continues to increase in Ontario, recent waiting lists must be due to a disproportionate growth in demand. There was no convincing evidence of age-related or sex-related discrimination in allocating this limited resource. Supply-demand mismatch was driven above all by the continued increase in CABG use among elderly people.

Coronary artery bypass grafting in Canada: What is its rate of use? Which rate is right?

We reviewed recent reports from administrative databases and clinical registries addressing the utilization of coronary artery bypass grafting (CABG) in Canada. The Canadian CABG rate per 100,000 people increased from 31.1 to 43.2 between 1981-82 and 1986-87. Between 1981 and 1986 the rate in the United States increased from 69.9 to 95.3 per 100,000, consistently about two times the Canadian rate. Provincial data have shown particular growth in utilization among elderly people. However, in the United States the 1985 CABG rate was twice as high as the aggregated age-specific rates for Ontario and Manitoba among people 65 to 74 years of age and four times higher among those 75 years or more. Limited registry data suggest that the Canadian CABG case mix is similar to the case mix in major US centres and that, utilization growth notwithstanding, the procedure is largely applied to patients who should, in theory, benefit (i.e., those with severe angina, impaired left ventricular function and left main-stem or triple-vessel disease). However, chart audits and registry evaluations using explicit criteria are needed to compare the use of CABG in Canada and the United States. In addition, Canadian data show moderate regional and municipal variations, the 1986-87 rates per 100,000 population in major census metropolitan areas varying from 19.5 to 46.9. Areas with consistently low rates raise particular concerns about impaired access to CABG. Reasons for variations should therefore be a research priority.

False-positive coding for acute myocardial infarction on hospital discharge records: chart audit results from a tertiary centre.

Hospital medical records staff enter diagnostic codes on charts using the International Classification of Diseases (Clinically Modified), Ninth Revision (ICD-9-CM). In a downtown Toronto tertiary hospital, 209 consecutive charts coded for acute myocardial infarction as the primary diagnosis in 1987-88 were reviewed. Criteria for documentation of acute myocardial infarction included symptomatic, electrocardiographic and enzymatic elements. Forty-three (21%) false-positives, ie, charts coded acute myocardial infarction where criteria were not fulfilled, were found (95% confidence interval 15 to 26%). Physician diagnosis of acute myocardial infarction appeared on the face sheet of 30 of the false-positive cases. Common reasons for false-positive face sheet entries and chart coding were acute myocardial infarction within the previous eight weeks with transfer or readmission for coronary angiography and other procedures; and presumed acute myocardial infarction on admission subsequently unproven or disproved. The false-positive proportion was similar to a Canadian study drawing on charts from hospitals of various sizes in 1977, lower than in recent reports from various American tertiary teaching hospitals (P less than 0.0001), and higher than in five Boston area community hospitals (P = 0.0005) where procedure-related transfers or readmissions of previous acute myocardial infarction patients were less likely. This audit lends credence to arguments that changes are needed in ICD-9-CM codes for acute myocardial infarction and in the assignation of reasons for hospitalization.

Effects of residential exposure to environmental tobacco smoke on Canadian children.

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.

Coronary thrombolysis--clinical guidelines and public policy: results of an Ontario practitioner survey.

The Ontario Medical Association (OMA) guidelines for intravenous thrombolysis in acute myocardial infarction were released in March 1988 and contributed to a government decision against special per-case funding to assist hospitals using tissue-type plasminogen activator (tPA). In October 1988, 1512 cardiologists, internists and physician-administrators who were OMA members were mailed a questionnaire seeking their views on the OMA guidelines and related issues. Of the 419 questionnaires (28%) that were returned, 392 contained usable responses. Among the respondents 268 (68%) had used thrombolytic drugs in the preceding 12 months; the mean number of cases was 10.6 (standard deviation 12.9). A strong or a mild preference for tPA over streptokinase was registered by 64% of the respondents; 28% had no preference. However, the self-reported ratio of actual streptokinase:tPA use was about 3:1, and 73% indicated that the government's funding policy had limited the availability of tPA in their hospital. The respondents were almost equally divided as to whether the policy should be changed. The guidelines were deemed helpful by 85% of the noncardiologists, as opposed to 52% of the cardiologists (p less than 0.005). OMA involvement in developing and circulating such guidelines was supported by 74% of the respondents and opposed by 18%; opposition was more likely to come from those who found the guidelines unhelpful (p less than 0.001). Support for involvement by the College of Physicians and Surgeons of Ontario was much weaker (supported by 32%, opposed by 62%). Overwhelming opposition to government involvement was evident.

Mortality rates among patients with end-stage renal disease in Canada, 1981-86.

We assessed the mortality rates by age, sex, race, blood type, primary diagnosis, treatment and transplantation history of 8432 patients in Canada for whom end-stage renal disease (ESRD) was diagnosed between 1981 and 1986. Significant differences in the probability of dying were found between those with and without diabetes mellitus, between those who had received a renal transplant and those who had not, between white and nonwhite patients and between various age groups. The mortality rates of the ESRD patients were at least three times higher than those of the general Canadian population. Primary diagnosis and treatment were significantly associated with the risk of dying among the ESRD patients. For those who had received a transplant, the length of time spent waiting for a transplant was positively associated with the risk of death from ESRD. Patients who had received peritoneal dialysis before transplantation had a higher risk of death than those who had received either hemodialysis (risk ratio 1.3) or transplantation (risk ratio 3.2) as the first treatment. No significant differences were found in the cause of death between those who had received peritoneal dialysis and those who had received hemodialysis. Almost half of the deaths among women without diabetes who had received a transplant were due to infection.