The Tel Aviv Stroke Registry

Reports from various stroke registries have provided wide and extensive analyses of incidence, risk factors, new diagnostic procedures, and mortality.¹² There are recognized geographic variations in the incidence of and mortality from stroke, and these may provide a key to understanding of risk factors for cerebrovascular diseases. Moreover, the relative importance of different risk factors may vary among countries.

Israel has a heterogeneous population, of which a considerable proportion was born abroad. The people differ in their genetic background, as well as in their early environment, lifelong dietary patterns, and other habits. This country provides unusual opportunities for collecting information, since the medical facilities in Israel are of excellent quality and are equally accessible to all segments of the population, regardless of ethnic origin or socioeconomic status. However, only limited studies of stroke epidemiology in Israel are available.³⁴⁵

The Tel Aviv Stroke Registry (TASR) was established in 1988 as a prospective study using systematic computer coding of data from all patients admitted with stroke. Using the amassed data, we attempted to estimate the type and severity of stroke, define the profile of risk factors and outcomes, and detect potential differences in stroke profiles in different ethnic groups.

Subjects and Methods

Throughout the 6 years between May 1, 1988, and April 30, 1994, all stroke patients admitted to the Tel Aviv Medical Center (TAMC) were evaluated, examined, and registered by an experienced stroke team consisting of four dedicated and well-trained neurologists. The standard protocol included the demographic data, stroke description (eg, infarct, hemorrhage, transient ischemic attack), stroke distribution (eg, right or left hemisphere, brain stem, cerebellum, unknown), onset (eg, abrupt, gradual, stepwise, stuttering), presence or absence of headache, onset during sleep or wakefulness, and past medical history of vascular risk factors (eg, hypertension, ischemic heart disease, cardiac arrhythmias, congestive heart failure, peripheral vascular disease, diabetes mellitus, hyperlipidemia, smoking). Definitions of the various vascular risk factors are available from the authors.

The definitions of these risk factors are shown in Table 1. Strokes were divided into three degrees of severity based on activities of daily living: independence in these activities (mild), partial dependence (moderate), and complete dependence (severe). The severity was defined within 24 hours after admission. The patients with subarachnoid hemorrhage were excluded because of the different pathophysiology involved. Interrater agreement for the different items of evaluation was very good, with a high Kendall coefficient of concordance.⁶

The patients were divided into three groups based on country of birth (Europe/America, Asia/Africa, and Israel), and a fourth group was composed of individuals whose birthplace was unknown. Mortality was defined as death occurring before discharge from the hospital (in-hospital mortality). Patients with a suspected diagnosis of stroke underwent a standard protocol of investigations: brain CT in most of the patients, electrocardiography, electroencephalography, and routine blood and urine tests.

The stroke unit also has an active Doppler laboratory with a duplex device and transcranial Doppler operated by well-trained and experienced technicians. Digital subtraction angiography is performed in selected patients.

The patients' current medications were recorded, including antithrombotic drugs. Aspirin failure was defined as recurrence of stroke in patients taking aspirin.

Results

A total of 3600 consecutive patients with stroke were admitted to the TAMC during the study period. All patients were prospectively coded, and the findings were entered into a computerized data bank.

There were 2094 males (58.2%), and the mean±SD age was 73.2±10.7 years. The age distribution of these patients in relation to the population at risk in different age groups is shown in Table 1. The difference in age distribution between the TASR patients and the Tel Aviv population at large was significant (P<.01).

CT was performed in 77.3% of the patients, providing a differential diagnosis of hemorrhagic versus ischemic stroke. Cerebral infarctions were diagnosed in 2915 patients (81.0%) and primary intracerebral hemorrhages in 288 (8.0%). Transient ischemic attacks occurred in 397 patients (11.0%).

In terms of various vascular territories, in 1423 patients (39.5%) the stroke occurred in the right hemisphere and in 1608 (44.7%) in the left hemisphere; in 453 (12.6%) the stroke occurred in the vertebrobasilar region, and in 116 (3.2%) the site was unknown. The difference between right and left hemispheres was statistically significant (P<.001; z=−3.29, binomial distribution). In terms of stroke severity, it was mild in 46%, moderate in 17%, and severe in 37%.

The distribution of patients in terms of sex and ethnic origin was similar to that of the Tel Aviv population (Table 2).

The frequencies of the various risk factors in the ethnic groups are summarized in Table 3. A past medical history of hypertension was the most prominent factor, recorded in 52.2% (1879) of the patients, followed by diabetes mellitus (25.2%, 908). Ischemic heart disease was present in 29.7% (1069) of the stroke patients: 14.3% (514) of them had atrial fibrillation and 8.3% (299) had congestive heart failure. There were 613 (17.0%) patients with a history of cigarette smoking, and 8.5% (305) had hyperlipidemia.

Patients from Europe and America more frequently had ischemic heart disease and atrial fibrillation, whereas diabetes mellitus and smoking were more prevalent in the other groups (Table 3). Table 4 shows data taken from the literature⁷⁸ regarding the odds ratio of risk factors for stroke patients compared with control groups. Of the 3600 stroke patients, 861 (24.0%) were admitted with recurrent strokes (most of them were recurrent ischemic brain events) and 159 (18.5%) had more than one recurrent stroke. Ninety-two of the 861 patients (10.7%) died.

Table 5 shows the mortality rates and severity in the TASR. As a whole, with use of the linear trend test, there was no trend toward a decrease in mortality over the years.

Discussion

Epidemiological aspects of stroke have been studied in many countries by means of stroke registries,^{789101112131415161718} some of which were prospective and population-based^{913141617181920} while others were hospital-based.^7101112 Although the Tel Aviv Stroke Registry is a hospital-based registry, it has provided an unusual opportunity to evaluate all the segments of the Israeli population in terms of ethnic groups and origin. A much earlier multicenter study performed with the collaboration of the World Health Organization²¹ showed that the incidence rates for all types of stroke in Israel are similar to those in several European countries, but they are significantly less than those in Japan and Finland. The reasons for the discrepancy between Israel and other countries can only be speculated on; they apparently include genetic factors, stress, diet, lack of alcoholism, and the nature of the medical services providing treatment of risk factors such as hypertension.

As in previous reports from Israel⁴²⁰²² and other countries,⁸¹⁰¹³ we found that the proportion of males was greater (58.2%), which is in contradiction to the findings of Faulkes et al.¹¹ Headaches associated with the onset of risk were reported in 12.8% of our patients, whereas other registries recorded incidences of 9%⁷ and 23%.¹⁰ The differences could be due to different methods of data collection and varying definitions of headaches.

With stroke being a disorder associated with aging, the difference in age distribution between TASR patients and the general Tel Aviv population, as expected, was significant (P<.001), and the comparative age of the patients with stroke was significantly higher as well.

We noted the significant difference of laterality of the hemispheric stroke: in the left hemisphere it occurred more frequently than stroke in the right hemisphere.

We found the frequencies of the common risk factors for stroke in Israel to be similar to those of the other developed countries,²³²⁴ with significantly higher prevalence of hypertension (52%; Table 3). These results correspond with those of previous studies by other authors.^{45101625262728} Earlier comparisons of stroke and risk factor frequencies in each ethnic group with their frequencies in the same ethnic groups in the general population were impossible because of lack of data.²⁹³⁰ The distribution of the three main Israeli ethnic groups—European/American (Ashkenazi), Asian/African (Sephardic), and native Israeli populations—was registered in the TASR (Table 2). Our analysis of risk factors for stroke among the ethnic groups showed a significant trend toward a high frequency of ischemic heart disease and atrial fibrillation in the European/American group (P<.001), with diabetes mellitus and smoking being more prevalent in the other groups (P<.001). It was suggested that Ashkenazi Jews have a higher frequency of coronary atherosclerosis and therefore are predisposed to have a stroke.

Over the 6 years of the present study, a trend emerged showing a decline of stroke mortality among our stroke patients, a feature that was seen in other analyses of stroke deaths over the last two decades.¹⁶¹⁷¹⁸ This parallels the worldwide decline in cardiovascular diseases mortality. Mortality from coronary heart disease underwent a striking decline in Jews,²⁷ with the trend beginning even before the initiation of programs for the control of high blood pressure, hyperlipidemia, and cessation of smoking habits.^{16171820252631323334}

The TASR serves as a data bank, a concept that proved efficacious in providing a method for establishing a valuable clinical research data resource. The TASR has been a source for a series of clinical studies, including dealing with dementia after first-ever stroke,³⁵ failure of aspirin treatment after stroke,³⁶ electroencephalography as a predictor of dementia after first ischemic stroke,³⁷ and others. Thus, the TASR is a source of information for analysis of different aspects of stroke. It provides an opportunity for valuable understanding of the etiology and pathophysiology of different subtypes of stroke, in addition to facilitating the detection of mortality trends and determination of their causes.

Reprint requests to Dr N.M. Bornstein, Department of Neurology, Tel Aviv Medical Center, 6 Weizmann St, Tel Aviv, 64239, Israel.