Prevalence of Stroke in the General Population
The Rotterdam Study
Background and Purpose We assessed the prevalence of self-reported and medically confirmed stroke and the degree to which the event had led to hospitalization.
Methods From all participants of the Rotterdam Study, a population-based cohort study of 7983 subjects aged 55 years and older living in a suburb of Ommoord in Rotterdam, information on stroke history was obtained by the question, “Did you ever suffer from a stroke, diagnosed by a physician?” Supplementary medical information was obtained from general practitioner or hospital discharge records.
Results Prevalence of self-reported stroke was 2.5% in men aged 55 to 64 years, 5.0% in men aged 65 to 74 years, 8.9% in men aged 75 to 84 years, and 11.6% in men aged 85 years or older. Corresponding figures for women were 1.6%, 3.3%, 6.7%, and 10.5%, respectively. Of the self-reported strokes, 67% could be confirmed by medical information. In 53% (95% confidence interval, 47% to 60%) of subjects with a confirmed stroke, the event had led to hospital admission. The proportion of hospitalized patients decreased with age.
Conclusions The present study provides valid age- and sex-specific estimates of prevalence of stroke. A substantial proportion of patients with stroke is not hospitalized.
Surveys on stroke prevalence among the general population may provide valuable information for planning of healthcare services. Few such studies, however, have been conducted in Europe, and those available were conducted at least one decade ago.1 2 We assessed the prevalence of self-reported stroke in a sample of the general Dutch population, compared self-reports with additional medical information, and determined the frequency of hospitalization.
Subjects and Methods
The Rotterdam Study is a single center cohort study of 7983 subjects aged 55 years or older living in the suburb of Ommoord in Rotterdam, Netherlands. The study includes residents of six homes for the elderly (897 participants) and is approved by the Medical Ethics Committee of Erasmus University.3 Written informed consent was obtained from all participants. Overall response was 78%.
A history of stroke was determined on the basis of the question, “Did you ever suffer from a stroke, diagnosed by a physician?” Signs and symptoms had to last more than 24 hours. The number of strokes that had led to a hospital admission and that had occurred without hospitalization was determined, and age at first and last stroke was obtained. Of the 352 subjects who responded with “yes,” the general practitioner (GP) was asked for supplementary medical information, including a detailed history, information on neuroimaging, and copies of hospital discharge records. Information from the GP was obtained for 285 subjects (81%).
Stroke diagnosis was based on all available medical information. In case of no hospitalization, mention of a “cerebrovascular accident” in the GP records was required to confirm the self-reported information. When possible, information on signs and symptoms was used in the final classification. In case of hospitalization, the diagnosis of a neurologist was used. In case of a transient ischemic attack (TIA), events were evaluated by one of the investigators, a neurologist (P.J.K.), and classified as definite/probable or no TIA. Accordingly, self-reported stroke was classified into (1) stroke diagnosed by the GP only; (2) stroke diagnosed clinically by a neurologist; (3) stroke for which no distinction between diagnosis by a GP or a neurologist could be made with the available information; (4) no stroke but diagnosed as a TIA by either the GP or a neurologist; and (5) no stroke or TIA.
To optimize prevalence data, medical records of those subjects in homes for the elderly who were mildly to moderately cognitively impaired (n=332) were systematically reviewed.4 Stroke was considered present when in the medical records a cerebrovascular event (excluding TIA) was mentioned. The information obtained by systematic review is included in the prevalence estimates presented as “stroke confirmed by medical records.”
Complete information was available for 7661 subjects. Results are presented by age and sex.
The study population consisted of 3034 men (mean age, 69.9 years [SD, 8.5]) and 4627 women (mean age, 71.8 years [SD, 9.8]). Table 1⇓ presents a comparison of self-reported stroke with medically confirmed stroke. Subjects in the “no stroke or TIA” group had a variety of diseases, including cardiac disease, cervical syndrome, collapse of unknown cause, dizziness symptoms, epilepsy, headache, multiple sclerosis, Parkinson's disease, and subdural hematoma.
In subjects with mild to moderate cognitive impairment living in homes for the elderly (n=332), we identified 57 subjects with a previous stroke who had given a negative answer to the screening question. The prevalence of self-reported stroke and that of stroke confirmed by medical records are presented in Table 2⇓.
Of men aged 45 to 64 years with a confirmed stroke, 72% (95% confidence interval [CI], 56% to 87%) had been hospitalized. Of men aged 65 to 74 years and 75 years or older, 75% (95% CI, 62% to 88%) and 49% (95% CI, 32% to 65%) had been hospitalized, respectively. For women these figures were 74% (95% CI, 59% to 88%), 53% (95% CI, 36% to 70%), and 24% (95% CI, 14% to 34%), respectively.
In several cross-sectional studies in which self-reported stroke was evaluated by neurological examination, 10%5 to 50%1 2 was found to be a true stroke. Fourteen percent of the self-reported strokes appeared to be TIAs.6 Our results are in agreement with these findings.
A limited number of population-based studies on the prevalence of stroke has been performed in industrialized countries.1 2 7 8 9 10 Comparison of age- and sex-specific prevalence estimates of stroke across studies is hampered by several factors, including differences in response, definition of stroke, determination of false-negative responses, extent of medical confirmation, study period, and difference in incidence of stroke. Despite these sources of variation, however, no large differences in age- and sex-specific stroke prevalence are observed (Figure⇓).
Frequency of hospitalization ranges from 96% in Finland2 and 81% in Copiah County, Mississippi,7 to 64%11 and 55%12 in Great Britain. For the Netherlands, rates from 49% to 72% have been reported, which agrees with our estimates.13 14 Our results, however, are based on nonfatal strokes only and may be different when fatal strokes are included. Longitudinal studies are needed to address that issue.
In conclusion, the present study provides valid age- and sex-specific estimates of prevalence of stroke. Substantial proportions of patients with stroke are not hospitalized.
The Rotterdam Study is supported in part by the NESTOR program for geriatric research (Ministry of Health and Ministry of Education), the Municipality of Rotterdam, the Netherlands Heart Foundation, the Netherlands Organization for Scientific Research (NWO), and the Rotterdam Medical Research Foundation (ROMERES). The contribution to the data collection of the general practitioners of the suburb of Ommoord, the field workers, ultrasound technicians, computer assistants, laboratory technicians, and the Rotterdam Study physicians are gratefully acknowledged.
- Received February 19, 1996.
- Revision received April 22, 1996.
- Accepted May 17, 1996.
- Copyright © 1996 by American Heart Association
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