Stroke severity and outcome : in search of predictors using a population-based strategy

Abstract

This thesis, based on studies conducted in Örebro, the main municipality of Örebro County in Sweden, sought: 1) to determine the incidence rate and case fatality of first-ever stroke in a well-defined population; 2) to show the effects of selection bias on the frequency of different stroke characteristics; 3) to establish the incidence of neglect and anosognosia and their impact on disability; 4) to show the impact of pre-stroke risk factors on stroke severity and case fatality; and 5) to show the influence of stroke severity and other risk factor on one year mortality, on dependency after one year and on the risk of recurrent stroke.

All first-ever cases of stroke were registered during a 12-month period 1999-2000. The study population was 123,503. The WHO definition of stroke was used. Cases were searched inside as well as outside the hospital. Multiple overlapping sources and "hot pursuit" technique were used in the process of case ascertainment. Patients were investigated for the presence of neglect and anosognosia. The stroke severity was assessed, and the level of disability was established. Also, the following pre-stroke risk factors were noted: age, sex, living alone, hypertension, ischemic heart disease, heart failure, atrial fibrillation, diabetes, TIA, smoking, peripheral atherosclerosis, and dementia. The patients were followed for one year. Then survivors were examined at a follow-up visit, and once again their levels of impairment and disability were assessed.

Three hundred and eighty-eight cases of first-ever stroke were found, corresponding to a crude incidence rate of 314 (95% CI, 283 to 348) per 100,000 per year. Adjusted to the European population the corresponding rates were 254 (95% CI, 227 to 284) per 100,000 per year. The overall 28-day case-fatality rate was 19% (95% CI, 15 to 23). Eleven of the patients had subarachnoid haemorrhage, and were not subject to further investigations. When our results were compared to a national quality register 63% of the hospitalised patients were reported to the quality register. The case-fatality was lower in the national register. A larger proportion of the patients in the national register appeared to have been treated in a stroke unit and undergone rehabilitation, and computerised tomography seemed to have been done in a larger proportion. Twenty-three percent of testable first-ever stroke-patients suffered from unilateral neglect in the acute phase, while 17% showed signs of anosognosia. Both neglect and anosognosia showed independent influence on disability, anosognosia more so than neglect. Dementia, atrial fibrillation, and congestive heart failure were associated with more severe strokes, as well as with death within the first 28 days. Living alone was also associated with death within the first 28 days. Dementia, age, stroke severity, and atrial fibrillation were associated with death within a year. Dependency after a year was associated with age, stroke severity, and congestive heart failure. Stroke recurrence within a year was predicted by age, dementia, and ischaemic heart disease.

The incidence of first-ever stroke in Örebro was high, both from an international and a national perspective, and is comparable to that seen in other studies in northern and eastern Europe. Compared with other studies, the results support regional differences in stroke incidence within Scandinavia. The 28-day case-fatality is comparable to that seen in other Scandinavian studies. Outcome data get skewed when case ascertainment does not embrace all cases in a given area. A community-based stroke register is therefore the golden standard when measuring stroke incidence. It has not been shown previously that pre-stroke dementia is a risk factor for stroke severity, 28-day case-fatality, one-year mortality, and risk of having a recurrent stroke within a year. The studies confirm the results of previous research that certain heart diseases, especially atrial fibrillation and congestive heart failure, predispose for more severe strokes with a worse prognosis.