Recent trends in incidence of cerebral hemorrhage and infarction in Japan. A report based on death rate, autopsy case and prospective study on cerebrovasuclar disease

Stroke in a defined elderly population, 1967-1985. A less lethal and disabling but no less common disease

BACKGROUND AND PURPOSE

Decline in stroke mortality in recent decades has been well documented in the United States and other countries. This study, based on a well-defined population with comprehensive medical records available for research purposes, seeks to explain decline in stroke mortality among older persons between 1967 and 1985. The study specifically explores the competing explanatory mechanisms of decreased incidence of stroke versus decreased case-fatality rate.

METHODS

We conducted a retrospective analysis of three successive period cohorts (1967 through 1971, 1974 through 1978, and 1981 through 1985) of persons > or = 65 years of age enrolled in a large group model HMO in a metropolitan community. All new hospitalized and a sample of nonhospitalized strokes were ascertained, and samples of first-ever strokes were studied. Incidence, case-fatality rates, survival times, and comorbidities were compared across cohorts.

RESULTS

There was no significant change in stroke incidence over time; however, 1-month case fatality declined dramatically from 33% in 1967 through 1971 to 18% in 1981 through 1985 (P < .01); median survival increased from 213 to 1092 days. Indices of reduced severity included declines in coma from 27% to 12% (P < .01) and in wheelchair- or bed-bound status from 40% to 30% (P = .067). Cases with and without CT scan in 1981 to 1985, when this procedure became widely available in the health plan, were similar in severity, thereby reducing the possibility of ascertainment bias.

CONCLUSIONS

In this well-defined older population, stroke has become a less lethal and disabling though no less common disease. This finding fails to support the "compression of morbidity" hypothesis while supporting a model of delayed progression for stroke in this age group.

Coronary and cerebrovascular atherosclerosis: two aspects of the same disease or two different pathologies?

Cerebrovascular and coronary disease are characterized by some common aspects. Indeed the same risk factors relate to coronary heart disease and to cerebrovascular disease. However, there may be differences in the pathogenesis of atherosclerotic lesions in coronary and cerebral arteries. In fact some populations are characterized by a high incidence of ischaemic stroke and a low incidence of myocardial infarction, while in other populations there is an opposite trend. These differences could be explained on the basis of: genetic risk factors; a different prevalence of risk factors; a different reactivity of the coronary and cerebral arteries to risk factors; anatomical differences concerning coronary and extracranial cerebral arteries with respect to intracranial cerebral arteries. Atherosclerosis is undoubtedly a systemic disorder and its genetic and environmental causal factors are only partly known. The variable incidence of cerebrovascular and coronary heart disease in the same population or in different populations as well as the different nature of atherosclerotic plaques are probably related to the different prevalence of the causal factors, even though these may not always be identified.

Relationship between longitudinal changes in blood pressure and stroke incidence

The relationship of changes in blood pressure with time to stroke incidence was examined on members of the Adult Health Study sample who have participated in biennial clinical examinations at the Radiation Effects Research Foundation since their inception in 1958. The regression coefficient of blood pressure regressed on time (the increase in blood pressure per cycle) was used as an index of the change in blood pressure with time. Cox's regression analysis, a technique which is suitable for follow-up studies was used. The data suggest that a single blood pressure measurement is not sufficient for predicting risk; the accumulated value or average over a period of time should be considered for this purpose. In addition to the actual blood pressure, the increase in blood pressure with time is a risk factor, particularly for cerebral hemorrhage. Cerebral hemorrhage was more strongly related to diastolic than to systolic blood pressure, while cerebral infarction appeared to be more strongly related to systolic than to diastolic blood pressure.

Cerebrovascular diseases in a fixed population of Hiroshima and Nagasaki, with special reference to relationship between type and risk factors

A study was made of the incidence of cerebrovascular disease, the chronological trends, and the relationship between the disease types and risk factors in 16,491 citizens of Hiroshima and Nagasaki. The subjects underwent medical examination at least once between 1958-74, and were free of cerebrovascular disease at the initial examination. During the 16-year period, 1.162 cases of cerebrovascular disease developed in the study population, with diagnosis definite in 621. By type, there were 108 cases of cerebral hemorrhage, 469 cases of cerebral infarction, 33 cases of subarachnoid hemorrhage, and 11 cases of other unclassifiable types. As a risk factor of cerebral hemorrhage, elevation of systolic and diastolic blood pressure was the most closely related to onset, and left ventricular hypertrophy on electrocardiogram (ECG), and proteinuria were also related. However, a tendency was seen for the risk to be higher when the levels of serum cholesterol were lower. In cerebral infarction, aging like systolic blood pressure, was a most important risk factor. Left ventricular hypertrophy on ECG, proteinuria, and diabetes could also be risk factors. However, the relation to blood pressure, especially diastolic blood pressure, was not so great as in the case of cerebral hemorrhage.

The decline of stroke

Stroke mortality in the United States has declined since 1900. The mortality rates from stroke in Rochester, Minnesota, have declined 76% since 1950, and the primary cause for the declines is a decrease in the incidence of new cases of cerebral infarction and cerebral hemorrhage. There are no data on the incidence of stroke prior to 1945 to confirm the US mortality trend. The decline in incidence was noted in women 10-15 years before it was seen in men. Hypertension is the most important risk factor for stroke. Hypertension surveys have shown an increasing effectiveness of antihypertensive medication in lowering blood pressure, and the effect was noted earlier in women. Available evidence is consistent with the idea that treatment of hypertension is the only significant contributor to the decline of stroke.

A prospective study of cerebrovascular disease in Japanese rural communities, Akabane and Asahi. Part 1: evaluation of risk factors in the occurrence of cerebral hemorrhage and thrombosis

An epidemiological study of cerebrovascular disease in Akabane and Asahi, Japan, was made. (These cities are located near Nagoy, Japan.) The study population included 4,737 men and women aged 40 to 79 at the time of entry into the study. There were 4,186 persons who were examined and, of these, 264 cases of cerebrovascular attacks were observed between 1964 and 1970. The incidence rate of stroke in those persons not responding to the survey was 15.9 times higher than in those persons examined according to person-year observation in Akabane. The risk factors for cerebral hemorrhage and thrombosis were evaluated by age-adjusted and sex-adjusted relative risks. The predisposing factors to cerebral hemorrhage appeared to be high blood pressure, high left R wave, ST depression, T abnormality, capillary fragility counts, previous medical history of stroke and albuminuria. For cerebral thrombosis, the predisposing factors appeared to be high blood pressure, ST depression and funduscopic sclerotic findings, and those factors assumed to be significant were glycosuria and smoking habits. Ocular funduscopic abnormality was the most prominent risk factor for cerebral thrombosis, while high blood pressure and ECG abnormalities were highly related to cerebral hemorrhage. It was suggested that those subjects with a relatively higher blood pressure may have a higher relative risk of cerebral hemorrhage than those with a lower (normal range) blood pressure. A previous or family history of stroke also appeared significantly related to cerebral hemorrhage.

Current status of the epidemiology of brain infarction associated with occlusive arterial disease

Although large gaps in our knowledge concerning the epidemiology of cerebrovascular disease are apparent, careful inspection of all existing data now makes it possible to see certain patterns emerging which suggest certain risk factors for stroke.

While the problem of differential diagnosis of the various categories of cerebrovascular disease presents a major obstacle to obtaining an undistorted picture of the epidemiological features of stroke from death certificate mortality data, the addition of evidence from prospective studies, including those in Framingham, Massachusetts, reveals that various types of arterial occlusion with cerebral infarction are by far the most prevalent type of stroke. Any specific origin of atherosclerosis remains obscure, as possible etiological candidates including dietary alterations in salt, fat and refined carbohydrate, sedentary living, excessive calories promoting obesity, the cigarette habit and even the mineral content of water in addition to marital status have all been incriminated. However uncertain the final answer is, certain precursors for atherosclerosis, such as hypertension, diabetes, and hyperlipidemia, are important. Of these, hypertension is clearly the most important contributor to stroke incidence. Certain combinations of items carry more risk than do the same items singly. For example, the risk of a brain infarction in diabetics with hypertension is probably about six times that of normal subjects. In persons under 50 at the time of measurement risk of cerebral infarction is possibly ten times higher in those with hypertension and elevated lipids than in those without either elevated. This compounding of risk has pathogenetic, preventive and public health implications. For purposes of stroke screening alone the most efficient and practical method would be to determine casual blood pressure, although it must be stated that as yet there is uncertainty concerning the change in the risk if such blood pressure is treated.

Nationwide cerebrovascular disease morbidity study

Previous studies have noted that the geographic differences in stroke mortality among areas of the United States were not due to artifacts of certification practices or accuracy of the diagnosis. A study of hospitalized stroke patients was completed in order to determine whether the mortality differences were due to a higher incidence or case fatality following a stroke in areas with high stroke death rates. Eight of the nine areas that participated in the Nationwide Mortality Study were included in this study. A total of 2,619 stroke cases were ascertained including 1,631 (62.3%) who were alive at the time of hospital discharge, 937 (35.8%) dead at discharge, 46 (1.7%) who were discharged alive but died outside of the hospital, and five (0.2%) who were dead at discharge and certified by the medical examiner.

The incidence of stroke was higher in the high stroke death rate areas especially for men. The ratio of the incidence of stroke in men as compared to women was higher in the younger age groups (45–54, 55–64) and in the high-incidence as compared to low-incidence areas.

The case-fatality percentage was lowest in Denver and highest in South Carolina. Presence of coma on admission was the principal determinant of subsequent mortality in all areas.

Finally, there was no consistent difference in the distribution of symptoms of stroke among the areas, and diagnostic procedures were performed more often in urban than rural areas. Approximately 80% of the stroke cases could be substantiated by either an autopsy verifying diagnosis, arteriography, hemorrhagic spinal fluid, hemiplegia or coma on admission. Several hypotheses to explain the differences have been suggested as well as the need for new information.