Incidence and epidemiologic features of cerebrovascular disease (stroke) in Manitoba, Canada. Study of population 20-64 years of age

Oral contraception and risk of a cerebral thromboembolic attack: results of a case-control study

OBJECTIVE

To assess the risk of cerebral thromboembolism in women using low dose oral contraceptives.

DESIGN

A retrospective case-control study.

SETTING

All Danish medical, neurological, neurosurgical, and gynaecological departments.

SUBJECTS

All 794 women in Denmark aged 15-44 who had suffered a cerebral thromboembolic attack during 1985-9 and 1588 age matched randomly selected controls.

RESULTS

Of 692/1584 case/control questionnaires sent out, 590/1396 (85.3%/88.1%) were returned. Among the cases, 15 refused to participate, 69 had a revised or unreliable diagnosis, 40 had had thromboembolic disease previously, 13 were pregnant, and 152 had a disease predisposing to a cerebral thromboembolic attack. Of the 323 cases without a known predisposition, 320 reported use or non-use of oral contraception. Among the 1396 controls, eight refused to participate, were mentally retarded, or lived abroad; 18 returned an uncompleted questionnaire; 17 had had thromboembolic disease previously; 31 were pregnant; and 130 had a disease predisposing to a cerebral thromboembolic attack. Thus 1198 non-predisposed controls were available, among whom 1197 reported use or non-use of oral contraception. Among the 320 cases, 116 (36.3%) were oral contraceptive users at the time of the cerebral thromboembolic attack. By comparison there were 191 users (16.0%) among the 1197 controls, giving a crude odds ratio of 3.0. After multivariate analysis, including confounder control for age, smoking, years of schooling, and trend in use of different types of oral contraceptives during 1985-90, pills containing 50 micrograms oestrogen were associated with an odds ratio for cerebral thromboembolic attack of 2.9 (95% confidence interval 1.6 to 5.4), those containing 30-40 micrograms oestrogen an odds ratio of 1.8 (1.1 to 2.9), those containing progestogen only an odds ratio of 0.9 (0.4 to 2.4). The odds ratio did not change with increasing age or with duration of oral contraceptive use. A 50% increased risk of a cerebral thromboembolic attacks among cigarette smokers (after confounder control) was independent of oral contraception status and age.

CONCLUSION

Low dose oral contraceptives are associated with an increased risk of cerebral thromboembolic attack. Combined or sequential pills containing 30-40 micrograms oestrogen are associated with a one third reduced risk compared with preparations containing 50 micrograms oestrogen. Progestogen only pills did not increase the risk of a cerebral thromboembolic attack.

A collaborative study of stroke incidence in Japan: 1975-1979

A Japan Collaborative Study of Stroke covering 20 regional and occupational population groups was conducted with the support of the Ministry of Health and Welfare. In this study 17,423 males and 16,856 females, aged 40 to 69, were followed up prospectively from 1975 to 1979. The average annual incidence of all types of stroke was 3.94 for men and 2.52 for women per 1,000 population. The incidence of cerebral hemorrhage for men and women stood at 1.26 and 0.59 and that of cerebral infarction at 1.87 and 1.10 respectively. The difference in incidence between the sexes was large particularly in the age range of 40-49. The incidence of all types of stroke, cerebral hemorrhage and cerebral infarction increased with age. The incidence of all strokes in Japan during the period 1975-1979 appears to have decreased in comparison with that in 1960-1969, but tended to be still higher than that in Western countries.

Relative role of factors associated with cerebral infarction and cerebral hemorrhage. A matched pair case-control study

Comprehensive ascertainment of all possible new cases of stroke appearing between January 1, 1970 and June 30, 1971, and admitted to three major hospitals in Winnipeg, Manitoba, has been achieved by reviewing the Manitoba Health Services Commission claim reports. The medical records of these cases were reviewed, pertinent data were abstracted, and rigid criteria for diagnosis were followed. Also, data were obtained from death certificates, autopsy reports and long-term hospital records. A total of 606 ascertained cases (410 infarction, 137 hemorrhage, and 59 undetermined type) were matched for age, sex, residence and year of admission with 606 controls from admissions for other than cardiovascular and cerebrovascular disorders. The data were analyzed for elucidating the possible risk factors for infarction (INF) and hemorrhage (HGE). The findings suggested that hypertension was the main risk factor in hemorrhage, whereas in infarction, along with hypertension, other factors such as diabetes, heart enlargement in chest x-ray, ECG abnormalities, and smoking were suggested as risk factors. There was an association also between infarction, on one hand, and the history of receiving anticoagulants, diuretics, and medications for the heart, and the occurrence of myocardial infarction, on the other hand. These features indicate that infarction and ischemic heart disease have similar risk factors. Hemoglobin and hematocrit were higher in infarction cases than in their controls only when measured at stroke admission. No difference was revealed when they were measured prior to stroke. Their association with infraction therefore may be secondary to other factors and of no significance for its risk.