| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(Stroke. 2004;35:1047.)
© 2004 American Heart Association, Inc.
Original Contributions |
From National Centre of Work and Rehabilitation, Department of Health and Society, Linköping University, Linköping, Sweden.
Correspondence to Jennie Medin, National Centre of Work and Rehabilitation, Department of Health and Society, Linköping University, 581 83 Linköping, Sweden. E-mail jennie.medin{at}ihs.liu.se
| Abstract |
|---|
|
|
|---|
Methods All first-ever stroke patients aged 30 to 65 years in the Swedish Hospital Discharge Register between 1989 and 2000 were included.
Results The age-standardized, 3-year average incidence increased by 19%, from 98.9 to 118.0 per 100 000 among men, and by 33%, from 48.4 to 64.4 among women, between 1989 and 1991 and 1998 and 2000. The largest increase was seen among those younger than 60 years. On a county level, the change in age-standardized stroke incidence varied from small decreases (3%) to large increases (82%).
Conclusion Stroke incidence increased in Sweden for both men and women between 1989 and 2000. The increase was larger among women. This calls for action when it comes to studying risk factors and planning for prevention and health promotion and indicates the need for gender-specific studies.
Key Words: incidence stroke epidemiology
| Introduction |
|---|
|
|
|---|
The aim of this study was to estimate the trend in Sweden between 1989 and 2000 for first-ever stroke incidence among persons aged 30 to 65 years using routinely collected health statistics.
| Subjects and Methods |
|---|
|
|
|---|
The SHDR is maintained by the National Swedish Board of Health and Welfare and covers all public inpatient care from 1987 onward. Both patient-specific and administrative data are available.
A comparison of SHDR data and data from the Swedish Cause of Death Register (CDR) for the period 1987 to 1996 showed correspondence for 92% of the discharges.10 In the SHDR, the principal diagnosis or personal identification number were missing in <2% of cases.10 The coverage of the SHDR was reported to be at least 98% for somatic short-term care in an evaluation using statistics on hospital stays from the Federation of County Councils (FCC) in Sweden.10
The NSR is a Swedish register for quality assessment of acute stroke events that was established in 1994. Although reporting is not compulsory, almost all hospitals in Sweden that treat acute stroke patients participated in 1997. In this study, first-ever events from the NSR are presented only for the county of Östergötland.
Stroke was defined according to the WHO criteria as rapidly developing signs of focal or global disturbance of cerebral function lasting >24 hours (unless interrupted by surgery or death), with no apparent nonvascular cause.4 All strokes were classified according to the international classification of diseases ninth (ICD-9) and tenth revisions (ICD-10).
Patients were classified as having stroke cases if their discharge diagnosis was intracerebral hemorrhage (ICH: ICD-9-431; ICD-10-161), cerebral infarction (CI: ICD-9-434; ICD-10-163), or undetermined pathological type (UND: ICD-9-436; ICD-10-164). Transient ischemic attack (TIA: ICD-9-435; ICD-10-G45) and subarachnoid hemorrhage (SAH: ICD-9-430; ICD-10-160) were excluded.
Use of personal identification numbers made it possible to exclude patients in the register with stroke diagnoses on >1 occasion from 1987 onward. In such instances, the first occurrence involving a stroke diagnosis was counted.
Annual case-fatality ratios were defined as the proportion of stroke events that were fatal within 28 days of onset of first-ever stroke. Information on date of death was collected from the CDR.
| Statistical Methods |
|---|
|
|
|---|
To reduce fluctuations in yearly stroke incidence figure, over-time comparisons of stroke incidence were based on 3-year average incidence rates (eg, 1989 to 1991 through 1998 to 2000). Confidence intervals (95% CI) were calculated using a Poisson distribution.14
Because discharge with a stroke diagnosis is the basis for case ascertainment in this study, using the term "stroke incidence" may be somewhat misleading, because the procedure captures the discharge of "old" strokes rather than the occurrence of new strokes. However, because most stroke cases are discharged rather rapidly or die soon after their stroke,15 it is our view that the discharge data serve as a reasonable approximation of "real" incidence data.
| Results |
|---|
|
|
|---|
|
The age-standardized, 3-year average incidence rate for those aged 30 to 65 years increased by 19%, from 98.9 to 118.0 per 100 000 for men, and by 33%, from 48.4 to 64.4 per 100 000 for women, between 1989 to 1991 and 1998 to 2000 (Table 1).
|
The distribution of different subtypes of stroke was similar among men and women and, as seen in Figure 2, CI accounted for the majority of cases. The proportion of reported CI increased from 60% in 1989 to 75% in 2000. The percentage of reported ICH was stable and the proportion of reported UND decreased between 1989 and 2000, from 21% in 1989 to 7% in 2000.
|
The case fatality for all strokes decreased between 1989 to 1991 and 1998 to 2000 among men (from 21% to 12%) and women (from 19% to 14%).
In those aged 30 to 65 years, the age-standardized stroke incidence increased in all 21 counties between 1989 to 1991 and 1998 to 2000 for men, and in all but 2 counties for women. The age-standardized stroke incidence among men ranged from an increase of 3% to 62%, and from a 3% decrease to an increase of 82% among women.
In Table 2 we compare SHDR data with data on stroke trends for the age group 25 to 79 years from studies conducted in Sweden between 1985 and 2000. The stroke incidence estimated from SHDR data are lower than the incidence presented in the WHO MONICA studies4,6 and in the study conducted in Örebro, by Appelros.16
|
| Discussion |
|---|
|
|
|---|
Several factors may contribute to the increase in stroke in Sweden. These include an increase in well-documented lifestyle-associated risk factors such as obesity, sedentary lifestyle, smoking, and heavy drinking.2024 Migraine and oral contraceptive use are 2 other risk factors among young women.25 The prevalences of overweight and heavy alcohol consumption (among people younger than age 65 years) have increased in Sweden in recent decades.26 Although the prevalence of smoking has decreased since the 1960s in men and since the 1970s in women, the generations of women studied here experienced the highest smoking prevalence rates in Sweden.27
The data from the SHDR were available on a county level, thereby allowing comparison with regional Swedish studies (Table 2). Rather large differences in estimated incidence were seen. Among the reasons for the differences observed are geographical coverage discrepancies. The SHDR covers the county of Västra Götaland, whereas the WHO MONICA study was confined to the city of Gothenburg, which is situated in this county.4 Similarly, whole-county SHDR data were compared with city-specific data for Örebro16 and Lund-Orup.7 The county-specific data of the SHDR therefore cover wider and more rural areas. Other reasons are differences in time period (Table 2), inclusion of recurrent strokes,4,6 and inclusion of diagnoses other than CI, ICH, and UND (eg, subarachnoid hemorrhage).4,7,8,16 Finally, many of the regional studies with procedures for excluding cases not belonging to the region undergoing study probably make more precise estimations of the underlying population than in the present study, which relies on official population statistics.11
Compared with the NSR, the SHDR the incidence figures are higher for men and women (Table 2). According to Appelros,28 the NSR appears to miss >30% of the strokes, because lack of beds in the special stroke units implies treatment on general wards, where there is less awareness about reporting strokes to the NSR.
| Methodological Aspects |
|---|
|
|
|---|
Regarding stroke sequelae, we included patients, according to their unique personal identification number, the first time they appeared in the register. Nevertheless, we still do not know if they had their first-ever stroke before 1987. However, because the studied population is young, and because stroke is a rare disease in younger persons, recurrent strokes are thus uncommon.
Misclassification
Lindblad et al31 validated inpatient discharge diagnoses from 3 hospitals in 1 Swedish county and the diagnosis of stroke was confirmed in 94% of first-ever strokes. However, Stegmayr30 compared data from 1985 to 1989 obtained in the WHO MONICA northern Sweden study with inpatient data from the SHDR. Among those discharged alive, 32% of stroke diagnoses were false-positives and 6% of nonstroke diagnoses were false-negatives. The most common reasons for false-positive stroke diagnoses were that stroke sequelae, TIA, or patients with diffuse symptoms had been coded as acute stroke.
Other validation studies in the Nordic countries report a high validity for the diagnosis of acute stroke in their national hospital discharge registers.32,33 A Finnish study reported that during the period 1985 to 1993, there was an agreement on diagnosis in 90%.33 A Norwegian study conducted between 1994 and 1996 showed that 4.6% of the discharge diagnoses were classified as nonstroke diagnoses after validation.32 This study32 also contended that hospital discharge data may overestimate stroke incidence if the diagnoses are not restricted to ICD-9 codes 430, 431, 434, and 436, which are the same diagnoses that are studied here. According to Leppälä33 and Ellekjaer,32 hospital discharge diagnoses are valuable sources of information when it comes to epidemiological studies, health planning, and research.
As was seen in Figure 2, the classification of stroke as UND has decreased in favor of specific stroke diagnoses. The increased use of computerized tomography (CT) since the 1980s probably reduced the high false-positive rate,8,31 especially in younger age groups in which, according to Johansson,7 it is easier to diagnose stroke, because symptoms are not complicated by comorbidity such as dementia and osteoarthrosis. The trend for TIAs observed between 1985 and 1994 in a French register was stable over time, and the observed increase in incidence of ischemic stroke in that register appeared to be disease-specific.34 Furthermore, an increase in incident stroke cases caused by improvements in diagnostic techniques alone is likely to affect men and women similarly within the same county. In this study, the incidence trend in several counties was rather different among men and women, with a much larger increase for women in most counties.
Given the high false-positive rate in relation to the false-negative rate, improved classification is not likely to have caused a spurious increase in stroke incidence.
The increased use of CT may have increased the detection of less severe strokes.8,31 Case fatality (28-day mortality) is a marker of disease severity. Denmark, Sweden, and Finland have low case-fatality rates.35 The decrease in case fatality observed in this study is in line with other Swedish studies.8 The increase that is reported in the SHDR therefore may be partly because of an increase in detection of less severe strokes. Indeed, previous studies show that in the western world, stroke has become a disease of less severity.36,37
| Conclusions |
|---|
|
|
|---|
Received September 2, 2003; revision received January 29, 2004; accepted January 30, 2004.
| References |
|---|
|
|
|---|
2. Murray CJL, Lopez AD. Alternative projections of mortality and disability by cause 19902020: Global Burden of Disease Study. Lancet. 1997; 349: 14981504.[CrossRef][Medline] [Order article via Infotrieve]
3. County Council of Östergötland. The medical program for stroke. Linköping: County Council of Östergötland. 1997. In Swedish.
4. Thorvaldsen P, Kuulasmaa K, Rajakangas A-M, Rastenyte D, Sarti C, Wilhelmsen L. Stroke trends in the WHO MONICA project. Stroke. 1997; 28: 500506.
5. Stegmayr B, Asplund K, Wester P. Trends in incidence, case-fatality rate, and severity of stroke in northern Sweden, 19851991. Stroke. 1994; 25: 17381745.[Abstract]
6. Stegmayr B, Vinogradova T, Malyutina S, Peltonen M, Nikitin Y, Asplund K. Widening gap of stroke between east and west. Eight-year trends in occurrence and risk factors in Russia and Sweden. Stroke. 2000; 31: 28.
7. Johansson B, Norrving B, Lindgren A. Increased stroke incidence in Lund-Orup, Sweden, between 1983 to 1985 and 1993 to 1995. Stroke. 2000; 31: 481486.
8. Pessah-Rasmussen H, Engstrom G, Jerntorp I, Janzon L. Increasing Stroke incidence and decreasing case fatality, 19891998: a study from the stroke register in Malmo, Sweden. Stroke. 2003; 34: 913918.
9. Terent A. Increasing incidence of stroke among Swedish women. Stroke. 1988; 19: 598603.
10. Spetz C-L. Statistics-Health and Diseases. In-patient diseases in Sweden 19871996. Stockholm, Sweden: The National Board of Health and Welfare Centre for Epidemiology; 1999.
11. Statistika centralbyrån. [Statistics Sweden.] Available at: http://www.scb.se. Accessed December 12, 2003.
12. Waterhouse J, Muir C, Correo P, Powell J. Cancer incidence in five continents. Lyon, France: International agency for research on cancer; 1976.
13. Appelros P. Stroke severity and outcome. In search of predictors using a population-based strategy. Neurotec Department, Karolinska Institutet, Stockholm and the Departments of Neurology and Geriatrics, Örebro University Hospital, Örebro, Sweden; 2002.
14. Fisher LD, Belle GV. Biostatistics: A methodology for the health sciences. New York, New York: John Wiley & Sons, Inc; 1993.
15. Glader E-L. Hospital care and patient follow-up based on Riks-Stroke, the National Quality Register for stroke care. Umeå: Umeå University, Sweden; 2003.
16. Appelros P, Nydevik I, Seiger Å, Terént A. High incidence rates of stroke in Örebro, Sweden: further support for regional incidence differences within Scandinavia. Cerebrovasc Dis. 2002; 14: 161168.[Medline] [Order article via Infotrieve]
17. Hulter-Åsberg K, Parow A. Event, incidence, and fatality rates of cerebrovascular diseases in Enköping-Håbo, Sweden, 19861988. Scand J Soc Med. 1991; 19: 134139.[Medline] [Order article via Infotrieve]
18. Jorgensen H, Plesner A, Hubbe P, Larsen K. Marked increase of stroke incidence in men between 1972 and 1990 in Frederiksberg, Denmark. Stroke. 1992; 23: 17011704.
19. Ellekjær H, Holmen J, Indredavik B, Terent A. Epidemiology of stroke in Innherred, Norway, 1994 to 1996: incidence and 30-day case-fatality rate. Stroke. 1997; 28: 21802184.
20. Bonita R, Duncan J, Truelsen T, Jackson RT, Beaglehole R. Passive smoking as well as active smoking increases the risk of acute stroke. Tob Control. 1999; 8: 156160.
21. Goldstein LB, Adams R, Becker K, Furberg CD, Gorelick PB, Hademenos G, Hill M, Howard G, Howard VJ, Jacobs B, Levine SR, Mosca L, Sacco RL, Sherman DG, Wolf PA, del Zoppo GJ. Primary prevention of ischemic stroke: a statement for healthcare professionals from the stroke council of the American Heart Association. Stroke. 2001; 32: 280299.
22. Haapaniemi H, Hillbom M, Juvela S. Lifestyle-associated risk factors for acute brain infarction among persons of working age. Stroke. 1997; 28: 2630.
23. Kuller LH. Epidemiology and prevention of stroke, now and in the future. Epidemiol Rev. 2000; 22: 1417.
24. Rexrode KM, Hennekens CH, Willett WC, Colditz GA, Stampfer MJ, Rich-Edwards JW, Speizer FE, Manson JE. A prospective study of body mass index, weight change, and risk of stroke in women. JAMA. 1997; 277: 15391545.
25. Bousser MG. Stroke in women: the 1997 Paul Dudley White International Lecture. Circulation. 1999; 99: 463467.
26. Boström G. Chapter 6. Habits of life and public health. Scand J Public Health. 2001; 58: 133166.
27. Nordlund A. Smoking and cancer among Swedish women. The Tema Institute, Department of Health and Society. Linköping University. 1997.
28. Appelros P, Högerås N, Terént, A. Case ascertainment in stroke studies: the risk of selection bias. Acta Neurol Scand. 2002; 107: 145149.
29. Sudlow CL, Warlow CP. Comparing stroke incidence worldwide. What makes studies comparable? Stroke. 1996; 27: 550558.
30. Stegmayr B, Asplund K. Measuring stroke in the population: quality of routine statistics in comparison with a population-based stroke registry. Neuroepidemiology. 1992; 11: 204213.[Medline] [Order article via Infotrieve]
31. Lindblad U, Råstam L, Ranstam J, Peterson M. Validity of register data on acute myocardial infarction and acute stroke: the Skaraborg Hypertension Project. Scand J Soc Med. 1993; 21: 39.[Medline] [Order article via Infotrieve]
32. Ellekjær H, Holmen J, Krüger Ø, Terent A. Identification of incident stroke in Norway: hospital discharge data compared with a population-based stroke register. Stroke. 1999; 30: 5660.
33. Leppälä J, Virtamo J, Heinonen O. Validation of stroke diagnosis in the National Hospital Discharge Register and the Register of Causes of Death in Finland. Eur J Epidemiol. 1999; 15: 155160.[CrossRef][Medline] [Order article via Infotrieve]
34. Lemesle M, Milan C, Faivre J, Moreau T, Giroud M, Dumas R. Incidence trends of ischemic stroke and transient ischemic attacks in a well-defined French population from1985 through 1994. Stroke. 1999; 30: 371377.
35. Thorvaldsen P, Asplund K, Kuulasmaa K, Rajakangas A-M, Schroll M. Stroke incidence, case fatality, and mortality in the WHO MONICA project. Stroke. 1995; 26: 361367.
36. Peltonen M, Stegmayr B, Asplund K. Time trends in long-term survival after stroke: the Northern Sweden Multinational Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA) Study, 19851994. Stroke. 1998; 29: 13581365.
37. Stegmayr B, Asplund K. Exploring the declining case fatality in acute stroke: population-based observations in the northern Sweden MONICA Project. J Intern Med. 1996; 240: 143149.[CrossRef][Medline] [Order article via Infotrieve]
This article has been cited by other articles:
![]() |
J. D. Lewsey, P. S. Jhund, M. Gillies, J. W.T. Chalmers, A. Redpath, L. Kelso, A. Briggs, M. Walters, P. Langhorne, S. Capewell, et al. Age- and Sex-Specific Trends in Fatal Incidence and Hospitalized Incidence of Stroke in Scotland, 1986 to 2005 Circ Cardiovasc Qual Outcomes, September 1, 2009; 2(5): 475 - 483. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. Harmsen, L. Wilhelmsen, and A. Jacobsson Stroke Incidence and Mortality Rates 1987 to 2006 Related to Secular Trends of Cardiovascular Risk Factors in Gothenburg, Sweden Stroke, August 1, 2009; 40(8): 2691 - 2697. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. D. Lewsey, M. Gillies, P. S. Jhund, J. W.T. Chalmers, A. Redpath, A. Briggs, M. Walters, P. Langhorne, S. Capewell, J. J.V. McMurray, et al. Sex Differences in Incidence, Mortality, and Survival in Individuals With Stroke in Scotland, 1986 to 2005 Stroke, April 1, 2009; 40(4): 1038 - 1043. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. E. Petrea, A. S. Beiser, S. Seshadri, M. Kelly-Hayes, C. S. Kase, and P. A. Wolf Gender Differences in Stroke Incidence and Poststroke Disability in the Framingham Heart Study Stroke, April 1, 2009; 40(4): 1032 - 1037. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. J. Goldacre, M. Duncan, M. Griffith, and P. M. Rothwell Mortality Rates for Stroke in England From 1979 to 2004: Trends, Diagnostic Precision, and Artifacts Stroke, August 1, 2008; 39(8): 2197 - 2203. [Abstract] [Full Text] [PDF] |
||||
![]() |
Md. S. Islam, C. S. Anderson, G. J. Hankey, K. Hardie, K. Carter, R. Broadhurst, and K. Jamrozik Trends in Incidence and Outcome of Stroke in Perth, Western Australia During 1989 to 2001: The Perth Community Stroke Study Stroke, March 1, 2008; 39(3): 776 - 782. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Towfighi, J. L. Saver, R. Engelhardt, and B. Ovbiagele A midlife stroke surge among women in the United States Neurology, November 13, 2007; 69(20): 1898 - 1904. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. Sundquist, X. Li, and K. Hemminki Familial Risk of Ischemic and Hemorrhagic Stroke: A Large-Scale Study of the Swedish Population Stroke, July 1, 2006; 37(7): 1668 - 1673. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Li, G. Engstrom, B. Hedblad, G. Berglund, and L. Janzon Blood Pressure Control and Risk of Stroke: A Population-Based Prospective Cohort Study Stroke, April 1, 2005; 36(4): 725 - 730. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. Pajunen, R. Paakkonen, H. Hamalainen, I. Keskimaki, T. Laatikainen, M. Niemi, H. Rintanen, and V. Salomaa Trends in Fatal and Nonfatal Strokes Among Persons Aged 35 to >=85 Years During 1991-2002 in Finland Stroke, February 1, 2005; 36(2): 244 - 248. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Stroke Home | Subscriptions | Archives | Feedback | Authors | Help | AHA Journals Home | Search Copyright © 2004 American Heart Association, Inc. All rights reserved. Unauthorized use prohibited. |