Research Acute case-fatality rates of stroke and acute myocardial infarction in a Japanese population: Takashima stroke and AMI registry, 1989–2005 Nahid Rumana1,2, Yoshikuni Kita1,3*, Tanvir Chowdhury Turin1,4, Yasuyuki Nakamura5, Naoyuki Takashima1, Masaharu Ichikawa6, Hideki Sugihara6, Yutaka Morita5,7, Kunihiko Hirose6,8, Kenzou Kawakami7,9, Akira Okayama10, Katsuyuki Miura1, and Hirotsugu Ueshima1 Background Few comprehensive stroke and acute myocardial infarction registries of long duration exist in Japan to illustrate trends in acute case-fatality of stroke and acute myocardial infarction with greater precision. We examined 17-year casefatality rates of stroke and acute myocardial infarction using an entire community-monitoring registration system to investigate trends in these rates over time in a Japanese population. Methods Data were obtained from the Takashima Stroke and AMI Registry covering a stable population of approximately 55 000 residents of Takashima County in central Japan. We divided the total observation period of 17 years into four periods, 1989–1992, 1993–1996, 1997–2000, and 2001–2005. We calculated gender, age-specific and age-adjusted acute case-fatality rates (%) of stroke and acute myocardial infarction across these four periods. Results During the study period of 1989–2005, there were 341 fatal cases within 28 days of onset among 2239 first-ever stroke events and 163 fatal cases among 433 first-ever acute myocardial infarction events. The age-adjusted acute casefatality rate of stroke was 14·9% in men and 15·7% in women. The age-adjusted acute case-fatality rate of acute myocardial infarction was 34·3% in men and 43·3% in women. The age-adjusted acute case-fatality rates of stroke and acute Correspondence: Yoshikuni Kita*, Science of Nursing, Tsuruga Nursing University, 78-2-1 Kizaki, Tsuruga-city, Fukui, Japan. E-mail: [email protected] 1 Department of Health Science, Shiga University of Medical Science, Shiga, Japan 2 Sleep Center, Foothills Medical Center, Calgary, Alberta, Canada 3 Tsuruga Nursing University, Tsuruga-city, Fukui, Japan 4 Department of Community Health Sciences, University of Calgary, Calgary, AL, Canada 5 Department of Cardiovascular Epidemiology, Kyoto Women’s University, Kyoto, Japan 6 Takashima General Hospital, Shiga, Japan 7 Makino Hospital, Takashima, Japan 8 Otsu Red Cross Hospital, Shiga, Japan 9 Shiga Medical Center for Adults, Shiga, Japan 10 The First Institute for Health Promotion and Health Care, Tokyo, Japan Received: 18 September 2013; Accepted: 4 March 2014; Published online 20 May 2014 Conflict of interest: None declared. Funding: Grants from The Research on Cardiovascular Disease (3A-1, 6A-5, 7A-2) and The Comprehensive Research on Cardiovascular and Life Style Related Diseases (H18-CVD-Ippan-029) of the Ministry of Health and Welfare, from the Grants-in-Aid Scientific Research (C-213670361, B-17390186, B-20390184, 17015018) of Ministry of Education, Culture, Sports, Science and Technology, and Japan Society of Promotion of Science (P-20.08124) Japan. Nahid Rumana was supported by the fellowship and Research Grants-In-Aid (P-21.09139) from the Japan Society for the Promotion of Science. DOI: 10.1111/ijs.12288 © 2014 World Stroke Organization
myocardial infarction showed insignificant differences across the four time periods. The average annual change in the acute case-fatality rate of stroke (−0·2%; 95% CI: −2·4–2·1) and acute myocardial infarction (2·7%; 95% CI: −0·7–6·1) did not change significantly across the study years. Conclusions The acute case-fatality rates of stroke and acute myocardial infarction have remained stable from 1989 to 2005 in a rural and semi-urban Japanese population. Key words: acute myocardial infarction, case-fatality, epidemiology, Japan, stroke, trend
Introduction Cardiovascular disease mortality has declined in many industrialized countries since the early 1970s (1,2). Similar trends for cardiovascular disease have also been observed in Japan (3–5). Although the stroke mortality rate started to decline steeply in Japan during the 1960s and 1970s (3), an even greater decline in stroke incidence has been observed during the last couple of decades (6). Despite decades of declining mortality from stroke, stroke was the third most common cause of death in 2000, when it accounted for 13·8% of total deaths (7). Even though the incidence and mortality of coronary heart disease (CHD) in Japan are reported to be among the lowest of all the industrialized countries (8–10), recent reports have suggested an increasing trend of acute myocardial infarction (AMI) in the Japanese population (11–13). However, there are only a few reports on contemporary trends in the acute case-fatality rates of stroke or AMI in Japan (14,15). A measurement of community trends in the incidence and case-fatality rate is necessary to determine whether a reduction in mortality is due to fewer events or improved survival after an event. A comprehensive disease registry is appropriate to monitor and track the incidence and case-fatality rates of diseases like AMI and stroke over time to estimate the trends in the burden of those diseases. Although the World Health Organization (WHO) launched an initiative in 1984 to monitor temporal trends in CHD and stroke, Japan was not part of that study (16). Very few cardiovascular disease registries covering an entire community exist in Japan to define trends in case-fatality rates of stroke or AMI over a prolonged time period. In accordance with the WHOMonitoring Trends and Determinants in Cardiovascular Disease (WHO-MONICA) (17–19), we have monitored stroke and AMI events in Takashima County, Shiga prefecture in Japan for a number of years, compiling information from disease registration covering the entire population of the county. The purpose of this study was to define the trends in case-fatality rates of stroke and AMI using a population-based disease registry that provides the most up-to-date information in a Japanese population. Vol 9, October 2014, 69–75
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Research Methodology Takashima stroke and AMI registry The Takashima Stroke and AMI Registry are an integrated part of the Takashima Cardio-cerebrovascular Disease Registration System, which was established in 1988 in Takashima County, Shiga, Japan (20–23). The objective of this registry is to measure trends in the incidence and case-fatality rates of stroke and AMI, and to compare these trends both inside and outside of Japan (17,18). Catchment population characteristics Takashima County is a predominantly farming community with inhabitants mainly classified culturally into a single subgroup with similar standards of living. The population of the area remained stable over the 17-year study period. It is a farming community with inhabitants mainly classified culturally into the same subgroup with similar standards of living. The population was 55 451 (men 49·3% and women 50·7%) in the year 2000 (24). With an aging populace, 22·3% of the Takashima population is ≥65 years, which is higher than the proportion of 17·4% in all of Japan (24). Case identification and registration process The methods used to identify and register cases, diagnostic criteria, and items of registration and data quality control are described in detail elsewhere (20–23). The stroke and AMI diagnostic criteria employed in this study were established by the Monitoring System for Cardiovascular Disease commissioned by the Japanese Ministry of Health and Welfare (17,18). These criteria are in accordance with the WHO-MONICA Project. The registered patients included all residents of Takashima County, who were hospitalized with stroke or AMI in the county hospitals. Stroke and AMI patients who were residents of Takashima County, but visited or were referred to one of the three tertiary hospitals outside the county, were also included in the registry. Registered patients were monitored annually by death certification. Original death certificates were seen at the county health center with the permission of the Japanese Ministry of Public Management, Home Affairs, Post and Telecommunications, to establish the cause of death. Patients’ privacy was protected at all times. Approval for this study was obtained from the institutional review board of the Shiga University of Medical Science. Stroke was defined (18,19) as sudden onset of neurological symptoms, which continued for a minimum of 24 h or resulted in death. Diagnosis of stroke type was based on clinical symptoms as well as neurological imaging by computed tomography or magnetic resonance imaging. Stroke was categorized into cerebral infarction, cerebral hemorrhage, and subarachnoid hemorrhage or unclassified. All suspected AMI cases (17,19) in the population during the study period were identified and evaluated based on information from medical history, clinical symptoms, 12-lead electrocardiogram (ECG) and cardiac enzyme levels, including creatine phosphokinase (CPK) and CPK-MB. For cases of out-ofhospital cardiac death, ECG findings and cardiac enzymes levels were often not available. In such cases, we had to base the evaluation on the patient’s location and symptoms at onset and history of CHD. All this information for both stroke and AMI were col-
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N. Rumana et al. lected from emergency room and ambulance records, and was supplemented with death certificate data. Research physicians and epidemiologists cross-checked the records for absolute verification regarding eligibility for inclusion in the registry as an event. We used the conventional method of defining case-fatality, the 28-day case-fatality of stroke and AMI (17–19). Fatal events were defined as those in which the patient died within 28 days after the onset date (19). The day of onset was considered day 0, and the difference in calendar days was calculated by subtracting date of onset from the date of death. The case-fatality rate, expressed as a percentage, was defined as the proportion of all stroke events that were fatal. For example, patients that had a stroke were followed up for 28 days, and the 28-day case-fatality rate for strokes was the proportion of these patients that died during follow-up. Statistical analysis The present study covered the period from January 1, 1989 to December 31, 2005. We divided the total observation period of 17 years into four-year groups: 1989–1992, 1993–1996, 1997–2000, and 2001–2005. To examine age-specific trends in case-fatality rate, stroke and AMI onset age were categorized into two groups,
myocardial infarction showed insignificant differences across the four time periods. The average annual change in the acute case-fatality rate of stroke (−0·2%; 95% CI: −2·4–2·1) and acute myocardial infarction (2·7%; 95% CI: −0·7–6·1) did not change significantly across the study years. Conclusions The acute case-fatality rates of stroke and acute myocardial infarction have remained stable from 1989 to 2005 in a rural and semi-urban Japanese population. Key words: acute myocardial infarction, case-fatality, epidemiology, Japan, stroke, trend
Introduction Cardiovascular disease mortality has declined in many industrialized countries since the early 1970s (1,2). Similar trends for cardiovascular disease have also been observed in Japan (3–5). Although the stroke mortality rate started to decline steeply in Japan during the 1960s and 1970s (3), an even greater decline in stroke incidence has been observed during the last couple of decades (6). Despite decades of declining mortality from stroke, stroke was the third most common cause of death in 2000, when it accounted for 13·8% of total deaths (7). Even though the incidence and mortality of coronary heart disease (CHD) in Japan are reported to be among the lowest of all the industrialized countries (8–10), recent reports have suggested an increasing trend of acute myocardial infarction (AMI) in the Japanese population (11–13). However, there are only a few reports on contemporary trends in the acute case-fatality rates of stroke or AMI in Japan (14,15). A measurement of community trends in the incidence and case-fatality rate is necessary to determine whether a reduction in mortality is due to fewer events or improved survival after an event. A comprehensive disease registry is appropriate to monitor and track the incidence and case-fatality rates of diseases like AMI and stroke over time to estimate the trends in the burden of those diseases. Although the World Health Organization (WHO) launched an initiative in 1984 to monitor temporal trends in CHD and stroke, Japan was not part of that study (16). Very few cardiovascular disease registries covering an entire community exist in Japan to define trends in case-fatality rates of stroke or AMI over a prolonged time period. In accordance with the WHOMonitoring Trends and Determinants in Cardiovascular Disease (WHO-MONICA) (17–19), we have monitored stroke and AMI events in Takashima County, Shiga prefecture in Japan for a number of years, compiling information from disease registration covering the entire population of the county. The purpose of this study was to define the trends in case-fatality rates of stroke and AMI using a population-based disease registry that provides the most up-to-date information in a Japanese population. Vol 9, October 2014, 69–75
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Research Methodology Takashima stroke and AMI registry The Takashima Stroke and AMI Registry are an integrated part of the Takashima Cardio-cerebrovascular Disease Registration System, which was established in 1988 in Takashima County, Shiga, Japan (20–23). The objective of this registry is to measure trends in the incidence and case-fatality rates of stroke and AMI, and to compare these trends both inside and outside of Japan (17,18). Catchment population characteristics Takashima County is a predominantly farming community with inhabitants mainly classified culturally into a single subgroup with similar standards of living. The population of the area remained stable over the 17-year study period. It is a farming community with inhabitants mainly classified culturally into the same subgroup with similar standards of living. The population was 55 451 (men 49·3% and women 50·7%) in the year 2000 (24). With an aging populace, 22·3% of the Takashima population is ≥65 years, which is higher than the proportion of 17·4% in all of Japan (24). Case identification and registration process The methods used to identify and register cases, diagnostic criteria, and items of registration and data quality control are described in detail elsewhere (20–23). The stroke and AMI diagnostic criteria employed in this study were established by the Monitoring System for Cardiovascular Disease commissioned by the Japanese Ministry of Health and Welfare (17,18). These criteria are in accordance with the WHO-MONICA Project. The registered patients included all residents of Takashima County, who were hospitalized with stroke or AMI in the county hospitals. Stroke and AMI patients who were residents of Takashima County, but visited or were referred to one of the three tertiary hospitals outside the county, were also included in the registry. Registered patients were monitored annually by death certification. Original death certificates were seen at the county health center with the permission of the Japanese Ministry of Public Management, Home Affairs, Post and Telecommunications, to establish the cause of death. Patients’ privacy was protected at all times. Approval for this study was obtained from the institutional review board of the Shiga University of Medical Science. Stroke was defined (18,19) as sudden onset of neurological symptoms, which continued for a minimum of 24 h or resulted in death. Diagnosis of stroke type was based on clinical symptoms as well as neurological imaging by computed tomography or magnetic resonance imaging. Stroke was categorized into cerebral infarction, cerebral hemorrhage, and subarachnoid hemorrhage or unclassified. All suspected AMI cases (17,19) in the population during the study period were identified and evaluated based on information from medical history, clinical symptoms, 12-lead electrocardiogram (ECG) and cardiac enzyme levels, including creatine phosphokinase (CPK) and CPK-MB. For cases of out-ofhospital cardiac death, ECG findings and cardiac enzymes levels were often not available. In such cases, we had to base the evaluation on the patient’s location and symptoms at onset and history of CHD. All this information for both stroke and AMI were col-
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N. Rumana et al. lected from emergency room and ambulance records, and was supplemented with death certificate data. Research physicians and epidemiologists cross-checked the records for absolute verification regarding eligibility for inclusion in the registry as an event. We used the conventional method of defining case-fatality, the 28-day case-fatality of stroke and AMI (17–19). Fatal events were defined as those in which the patient died within 28 days after the onset date (19). The day of onset was considered day 0, and the difference in calendar days was calculated by subtracting date of onset from the date of death. The case-fatality rate, expressed as a percentage, was defined as the proportion of all stroke events that were fatal. For example, patients that had a stroke were followed up for 28 days, and the 28-day case-fatality rate for strokes was the proportion of these patients that died during follow-up. Statistical analysis The present study covered the period from January 1, 1989 to December 31, 2005. We divided the total observation period of 17 years into four-year groups: 1989–1992, 1993–1996, 1997–2000, and 2001–2005. To examine age-specific trends in case-fatality rate, stroke and AMI onset age were categorized into two groups,
