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Abstract Reprints 1. A meta-analysis of infant diet
and insulin-dependent diabetes mellitus: do biases play a role?
We evaluated the relation between early infant diet and insulin-dependent diabetes risk with a meta-analysis of 17 case-control studies. A summary of all studies indicated a moderate effect for exposure to breast-milk substitutes [odds ratio (OR) = 1.38; 95% confidence interval (CI) = 1.18-1.61] and cow's milk-based substitutes (OR = 1.61; 95% CI = 1.31-1.98) before 3 months of age. Fourteen studies relied on retrospectively collected infant diet data based on long-term maternal recall, which may be biased or inaccurate; three studies used existing infant diet records to assess exposure, thus lessening the possibility of recall bias or inaccurate data. The studies using existing records demonstrated little association compared with the studies relying on long-term recall. Studies in which the controls had a participation rate that was more than 20% lower than that of the cases showed a stronger diabetogenic effect of never being breast-fed (OR = 1.58) than studies whose cases and controls had similar participation rates (OR = 1.06). Thus, differences in the participation rates of cases and controls may have biased the results of these studies. This meta-analysis indicates that the weak association between infant diet and risk of diabetes mellitus may have methodologic explanations. 2. Seasonality in the clinical
onset of insulin-dependent diabetes mellitus in Finnish children
Seasonal patterns in the incidence of insulin-dependent diabetes based on 2,062 cases diagnosed at age 14 years or under in Finland are described for the years 1987-1992. Seasonal patterns were estimated presenting the data as short Fourier series up to three harmonics together with a possible linear trend. This method allows an arbitrary shape for the seasonal effect. Likelihood ratio tests and Akaike's information criterion were used to determine the number of harmonics necessary to model the seasonal pattern and to test differences among age- and sex-specific subgroups in the population. Seasonal patterns in incidence were compared between sexes and between the three 5-year age groups with each controlling for the other's effect. A significant seasonal pattern in the incidence of insulin-dependent diabetes was found for the sexes combined and for two age groups (0-9 and 10-14 years). A statistically significant seasonal pattern could be confirmed for males, but not for females. During a calendar year, one cycle with a decreased incidence of insulin-dependent diabetes in June was found among younger boys. Among older boys, there were two distinct cycles with a decreased incidence, the first in June and the second during November-December. The most visible seasonal pattern was a lower number of cases diagnosed in June, while during the rest of the year the incidence remained relatively stable and high. The average annual incidence was 35.6 per 100,000 persons without any upward peaks. Some factors related to Westernization or industrialization increase risk of colon cancer. It is believed widely that this increase in risk is related to the direct effects of dietary fat and fiber in the colonic lumen. However, the fat and fiber hypotheses, at least as originally formulated, do not explain adequately many emerging findings from recent epidemiologic studies. An alternative hypothesis, that hyperinsulinemia promotes colon carcinogenesis, is presented here. Insulin is an important growth factor of colonic epithelial cells and is a mitogen of tumor cell growth in vitro. Epidemiologic evidence supporting the insulin/colon-cancer hypothesis is largely indirect and based on the similarity of factors which produce elevated insulin levels with those related to colon cancer risk. Specifically, obesity, particularly central obesity, physical inactivity, and possibly a low dietary polyunsaturated fat to saturated fat ratio, are major determinants of insulin resistance and hyperinsulinemia, and appear related to colon cancer risk. Moreover, a diet high in refined carbohydrates and low in water-soluble fiber, which is associated with an increased risk of colon cancer, causes rapid intestinal absorption of glucose into the blood leading to postprandial hyperinsulinemia. The combination of insulin resistance and high glycemic load produces particularly high insulin levels. Thus, hyperinsulinemia may explain why obesity, physical inactivity, and a diet low in fruits and vegetables and high in red meat and extensively processed foods, all common in the West, increase colon cancer risk. We studied the trends from 1969 to the mid-1980s in the incidence and mortality of acute myocardial infarction and stroke in Swedish women residing in the Uppsala Health Care Region. We used data from the Inpatient Care and Causes of Death registers to obtain total first event incidence and mortality rates. In our population, there were 20,182 acute myocardial infarctions and 30,462 stroke events, and 17,359 and 21,336 deaths, respectively. We found an average overall annual increase of 1.3% in the age-standardized incidence of acute myocardial infarction during the 1970s, followed by decreasing rates during the early 1980s. Mortality was virtually unchanged. Notably, among women 45-49 years of age, we observed a rising trend during the whole period, whereas in the oldest age groups, the increase slowed and reversed in the latter years. Both the incidence and mortality for stroke declined steadily: the age-standardized incidence fell by an average of 2.1% per year for all stroke and 7.8% for intracerebral hemorrhage. The falling rate of stroke was best explained by birth cohort effects, with a 30% reduction in women born in 1920 and later as compared with those born in 1890. We conclude that important changes in Swedish women's cardiovascular health have taken place and that increasing cigarette smoking and hypertensive treatment are major determinants. 5. Cancer risk following
a community-based programme to prevent cardiovascular diseases
Background. The North Karelia project, a community-based programme for prevention of cardiovascular diseases in North Karelia in 1972-1977, was successful in reducing some major cardiovascular risk factors. It was studied whether changes in the incidence of smoking- or diet-related cancers in North Karelia were different from those in a reference area without a programme. Methods. Poisson age-period-cohort-county regression models were fitted to each cancer-sex combination. Specially designed variables were added to the best models to detect any post-programme changes in the incidence trend in North Karelia. Results. After having been consistently higher, the incidence of lung cancer among males in North Karelia decreased below that of the reference county during 1987-1991. The programme-related risk ratio in 1987-1991 indicated a significant 20% beneficial effect. The trend in stomach cancer among males was more favourable in the reference county than in North Karelia. Conclusion. The quicker reduction in smoking may have caused the more favourable trend of lung cancer among North Karelian males than males in the reference county. 6. Employment and coronary risk
in women at midlife: a longitudinal analysis This study investigated the relation between employment and cholesterol in 541 women aged 42-50 years who resided in Allegheny County, Pennsylvania, in 1985-1988. Employment, health-related variables, and cholesterol were assessed at baseline and 3 years later. At baseline, employed and nonemployed women did not differ in cholesterol or health behaviors. However, women employed at baseline had a significant decrease in total high density lipoprotein cholesterol (1.9 mg/dl) and high density lipoprotein2 cholesterol subfraction (3.2 mg/dl) at follow-up. Those who were employed at both assessments had the lowest high density lipoprotein cholesterol at follow-up. These effects could not be accounted for by sociodemographics or employment quality variables. Post hoc analyses were conducted to examine health behaviors as a potential mechanism to account for the association between employment status and cholesterol. Over the study period, those who were employed at baseline were less likely to increase exercise and more likely to gain weight than those who were not employed at baseline. With menopause-related changes in metabolism, this can result in detrimental effects for cholesterol levels and coronary health. The results highlight the importance of longitudinal assessment in the study of employment and health. 7. Physical exercise and reduced risk of nonfatal myocardial infarction Gerald T O'Connor, Charles H Hennekens, Walter C Willett, Samuel Z Goldhaber, Ralph S Paffenbarger Jr, Jan L Breslow, I-Min Lee, Julie E Buring Am J Epidemiol 1995;142(11):1147-56 While the inverse association between physical activity and coronary heart disease risk is well documented, questions remain regarding the intensity of exercise, the potential for confounding by other risk factors for coronary heart disease, and the role of blood lipids and apolipoproteins. The authors examined these issues in the Boston Area Health Study, a case-control study of 340 patients (266 men, 74 women) who survived a first myocardial infarction between January 1, 1982, and December 31, 1983, and 340 controls matched on sex, age, and residence. The relative risk of myocardial infarction for those in the highest quartile of physical activity, compared with the lowest, was 0.50 (95 percent confidence interval (CI) 0.31-0.80) for men and 1.00 (95 percent CI 0.41-2.43) for women. When subjects were categorized by level of energy expenditure on moderate to vigorous sports alone, men in the most active category had 0.39 (95 percent CI 0.23-0.69) times the risk of those in the least active category, and women, 0.43 (95 percent CI 0.15-1.26) times the risk. Adjustment for body mass index, smoking, alcohol intake, diet, personal and family medical history, and personality type did not substantially change results nor did further adjustment for blood lipids. This was not surprising as total energy expenditure was uncorrelated with blood lipids or apolipoproteins. Moderate to vigorous sporting activity, however, appeared to be directly related to high density lipoprotein (HDL) cholesterol (p = 0.06), especially the HDL2 subfraction (p = 0.10). In these data, findings suggest that physical activity is inversely related to myocardial infarction risk, independently of other risk factors for coronary heart disease. 8. Influence of systolic and diastolic
blood pressure on stroke risk: a prospective observational study The purpose of this study was to estimate the influence of systolic (SBP) and diastolic blood pressure (DBP)on stroke risk. The Copenhagen City Heart Study is a prospective survey of 19,698 women and men who were invited to two cardiovascular examinations at 5-year intervals. Blood pressure was measured in participants once at each examination, together with other variables. Initial cases of stroke and transient ischemic attack were recorded from hospital records and death certificates from 1976 through 1988. When entered separately in the Cox regression model, both SBP and DBP had significant effects on stroke risk. In the lower 60% of the blood pressure distribution in the population, the relative risk of stroke was nearly constant, followed by a gradual increase in the upper 40% of blood pressure distribution. However, when SBP and DBP were entered simultaneously in the model, the effect of DBP vanished, while the pattern of the association between SBP and stroke risk remained unchanged. Persons on antihypertensive treatment had higher risk for stroke than non-treated persons with the same blood pressure, relative risk = 1.6 (95% confidence interval (CI) 1.2-2.2). The relative risk for the highest SBP levels, shared by nearly 3% of the population, was 4.0 (95% CI 2.2-7.3). The attributable risk of SBP in the upper 40% of SBP distribution, i.e., above the mean for each age and sex group, was 22%. Our results indicate that: 1) the association between blood pressure and stroke risk was not log-linear, and 2) SBP was a stronger stroke predictor than DBP. 9. Maternal asthma and idiopathic
preterm labor Previous studies suggest that women with asthma are at increased risk of preterm birth. Moreover, drugs (especially b-agonists) used to treat asthma are also used to treat preterm labor. The authors carried out a case-control study of 555 women from three hospital centers with idiopathic preterm labor (<37 weeks), including two overlapping (i.e., non-mutually exclusive) subsamples: cases with early idiopathic preterm labor (<34 weeks) and cases with idiopathic recurrent preterm labor (<37 weeks plus a previous history of preterm delivery or second-trimester miscarriage). Controls were matched to cases according to race and smoking history prior to and during pregnancy. All subjects responded in person to questions about atopic, respiratory, obstetric, and sociodemographic histories. Subjects in the early and recurrent preterm labor subsamples were also asked to undergo spirometric testing with methacholine challenge 6-12 weeks after delivery. Cases were significantly more likely to report histories of asthma symptoms and physician-diagnosed asthma (matched odds ratios of 2-3) than controls, particularly those cases with recurrent preterm labor. No significant associations were observed, however, with methacholine responsiveness. These results could not be explained by residual confounding by smoking or other variables, nor by selective recall of asthma symptoms and histories by cases. Women with asthma are at increased risk of idiopathic preterm labor. The fact that no such association was seen with methacholine responsiveness suggests that nonatopic, noncholinergic mechanisms may link bronchial and uterine smooth muscle lability. 10. Low blood lead levels in Northern
Ontario-what now? Objective: To assess the extent of childhood lead exposure and provide guidance for public health efforts to reduce exposure in Northern communities in Ontario. Design: Population-based cross-sectional survey. Setting: Northern Ontario, September-October 1992. Participants: 395 children aged 1 to 6 living in Moosonee or Moose Factory (68% of all children in target group). Outcome measures: Blood lead levels. Results: The geometric mean lead level was 3.10 mg/dL (range, 0 to 18.9 mg/dL); 4% of children had a lead level >10 mg/dL, and none had levels over 20 mg/dL. Two-year-olds and boys had the highest lead levels. Conclusions: Blood lead levels in this survey are low but unexpectedly close to inner city Toronto children in both non-point-source and point-source neighhourhoods. Population-level rather than individual interventions are required to further reduce exposure. Lead shot is among the important sources of insidious environmental lead exposure in this population and may be very important for some children involved in hunting activities. Results suggest the development of safer alternatives for lead shot. 11. Childhood and adolescent leukaemia in a North American population Peter Peizhong Wang, Carol S Haines Int J Epidemiol 1995;24(6):1100-9 Objective. This was to describe and analyse incidence and survival data on childhood leukaemias. Sample. Incident leukaemia cases aged 0-19 from the cancer registry holdings of the province of Saskatchewan for the 60-year period 1932-1991 are the subject of this descriptive report. Methods. Age-adjusted, age-specific, histologic-type specific, sex-specific, and cohort-specific incidence trends were reviewed. Univariate and multivariate survival analyses explored the effects of time period, age at diagnosis, gender, and histologic type. Results. Acute lymphocytic leukaemia (ALL) occurred more commonly in males and before the age of five; the 1982-1991 age-adjusted incidence is 3.1/100 000. Increasing incidence has been consistently noted, but has attenuated since 1971. The relative risk of developing ALL in the first 9 years of life, using children born from 1944 to 1948 as baseline, increased with each successive 5-year birth cohort until 1969-1973; since then the risk has been stable. Other histologic types were rare; over 60 years there were only 85 cases that could be grouped as acute non-lymphocytic leukaemias (ANLL); the 1982-1991 age-adjusted ANLL incidence is 0.6/100 000. A dramatic improvement in survival was seen over the last six decades, primarily for ALL. In ALL, children under five have better survival than older children and adolescents; the reverse is true for ANLL. Conclusions. ALL and ANLL are distinctive diseases clinically and the epidemiological findings are likewise distinctive. Our current ALL patterns are consonant with a number of other published reports. However, our small numbers of ANLL limit inferences. 12. Cohort study of Air Canada
pilots: mortality, cancer incidence, and leukemia risk Despite the special working environment and exposures of airline pilots, data on risk of death and cancer incidence in this occupational group are limited. The authors investigated a cohort of 2,740 Air Canada pilots who contributed 62,449 person-years of observation. All male pilots employed for at least 1 year on and since January 1, 1950, were studied. The cutoff date for outcome information was December 31, 1992. Standardized mortality ratio (SMR) and standardized incidence ratio (SIR) were used to compare mortality rates and cancer incidence rates of the cohort with the respective Canadian population rates. Ninety percent confidence intervals of the SMR and SIR were calculated. Statistically significant decreased mortality was observed for all causes (SMR = 0.63, 90% confidence interval (CI) 0.56-0.70), for all cancers (SMR = 0.61, 90% CI 0.48-0.76), and for all noncancer diseases (SMR = 0.53, 90% CI 0.45-0.62). Mortality from aircraft accidents was significantly raised (SMR = 26.57, 90% CI 19.3-35.9). Significantly decreased cancer incidence was observed for all cancers (SIR = 0.71, 90% CI 0.61-0.82), rectal cancer (SIR = 0.42, 90% CI 0.14-0.96), lung cancer (SIR = 0.28, 90% CI 0.16-0.46), and bladder cancer (SIR = 0.36, 90% CI 0.12-0.82). Prostate cancer (SIR = 1.87, 90% CI 1.38-2.49) and acute myeloid leukemia (SIR = 4.72, 90% CI 2.05-9.31) were significantly increased. The preferred relative risk model for radiation-induced nonchronic lymphoid leukemia (Beir V report) was applied to the cohort by using published estimates of in-flight radiation exposures. The estimated relative risk ranged from 1.001 to 1.06 and did not differ significantly from the observed SIR (SIR = 1.88, 90% CI 0.8-3.53). However, the incidence rate of acute myeloid leukemia was significantly increased. Monitoring of in-flight radiation exposure and long-term follow-up of civil aviation crew members is needed to further assess cancer incidence and leukemia risk in this special occupational group. 13. The 1993 General Social Survey
I: alcohol use in Canada Rates and correlates of alcohol use are reported from the 1993 General Social Survey, a household telephone survey of 10,385 Canadians carried out by Statistics Canada. Continuing a recent trend, alcohol use has declined. The portrait of the Canadian who is most likely to drink and drink heavily is that of a young adult male who is not married, relatively well-off, and rarely or never attends religious services. In a multivariate analysis of the combined impact of sociodemographic factors on drinking and drinking levels, it was found that the frequency of religious attendance and age were the strongest predictors of current drinking. Gender was the strongest predictor of volume of alcohol consumption, while religious attendance, age, marital status and employment status were also significant predictors. 14. The 1993 General Social Survey
II: alcohol problems in Canada Rates and correlates of problems associated with the use of alcohol are reported from the 1993 General Social Survey. Approximately 1 in 11 drinkers (9.2%) reported that drinking has had an adverse effect on his or her social life, physical health, happiness, home life or marriage, work or finances in the past year. The most commonly reported problems concerned physical health (5.1%), and financial position (4.7%). Approximately one in eight drinkers (12.9%) had driven a car within an hour after consuming two or more drinks in the previous year. Furthermore, more than two of every five respondents reported that they had experienced some problem due to other people's drinking. In a multivariate analysis, age, marital status, gender, religious attendance and employment status were the strongest predictors of problem drinking. The number of heavy drinking occasions is a stronger predictor of drinking problems than is overall level of consumption. 15.
Costs associated with gunshot wounds in Canada in 1991
Objective: To estimate the costs (in 1993 dollars) associated with gunshot wounds in Canada in 1991. Design: Cost analysis using separate estimates of gunshot incidence rates and costs per incident for victims who died, those who survived and were admitted to hospital and those who survived and were treated and released from emergency departments. Estimates were based on costs for medical care, mental health care, public services (i.e., police investigation), productivity losses, funeral expenses, and individual and family pain, suffering and lost quality of life. Setting: Canada. Outcome measures: Costs per case, costs by type of incident (e.g., assault, suicide or unintentional shooting) and costs per capita. Results: The total estimated cost associated with gunshot wounds was $6.6 billion. Of this, approximately $63 million was spent on medical and mental health care and $10 million on public services. Productivity losses exceeded $1.5 billion. The remaining cost represented the value attributed to pain, suffering and lost quality of life. Suicides and attempted suicides accounted for the bulk of the costs ($4.7 billion); homicides and assaults were the next most costly ($1.1 billion). The cost per survivor admitted to hospital was approximately $300,000; this amount included just over $29,000 for medical and mental health care. Conclusion: Costs associated with gunshot wounds were $235 per capita in Canada in 1991, as compared with $595 in the United States in 1992. The differences in these costs may be due to differences in gun availability in the two countries. This suggests that increased gun control may reduce Canada's costs, especially those related to suicide. 16. The effects of a 4-year program
promoting bicycle helmet use among children in Quebec Objectives. This study assessed the effectiveness of a 4-year program of bicycle helmet promotion that targeted elementary school children in one region of Quebec. The program revolved primarily around persuasive communication and community organization, combining standard educational activities and activities to facilitate helmet acquisition and use. Methods. Helmet use was compared between more than 8000 young cyclists in municipalities exposed or not exposed to the program. Factors influencing helmet use were controlled through the use of multivariate analyses. Results. Helmet use increased from 1.3% before program implementation to 33% in 1993. The program was clearly effective in most cycling circumstances and for various groups of children. However, the benefits of the program were unequally distributed; the program was one third as effective in poorer municipalities as in "average-rich" ones. Conclusions. This community-based program that combined various types of activities appeared to be effective. New intervention models are needed to ensure an equitable distribution of benefits.
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