Population-Based Incidence Rates of Subarachnoid Hemorrhage in Japan: The Shiga Stroke and Heart Attack Registry

Article information

J Stroke. 2022;24(2):292-295
Publication date (electronic) : 2022 May 31
doi : https://doi.org/10.5853/jos.2022.00087
aDepartment of Neurosurgery, Shiga University of Medical Science, Otsu, Japan
bDepartment of Digital Health and Epidemiology, Graduate School of Medicine and Public Health, Kyoto University, Kyoto, Japan
cDepartment of Public Health, Kindai University Faculty of Medicine, Osakasayama, Japan
dDepartment of Preventive Medicine and Public Health, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
eDepartment of Nursing Science, Tsuruga Nursing University, Tsuruga, Japan
fDepartment of Neurology, Shiga University of Medical Science, Otsu, Japan
gDepartment of Public Health, Shiga University of Medical Science, Otsu, Japan
hNCD Epidemiology Research Center, Shiga University of Medical Science, Otsu, Japan
Correspondence: Satoshi Shitara Department of Neurosurgery, Shiga University of Medical Science, Setatukinowacho, Otsu, Shiga 520-2192, Japan Tel: +81-77-548-2257 Fax: +81-77-548-2531 E-mail: s-shitara@umin.ac.jp
Received 2022 January 7; Revised 2022 January 7; Accepted 2022 February 3.

Dear Sir:

Stroke is the second leading cause of global deaths and disability-adjusted life years lost worldwide; although Japan had the highest stroke mortality in 1965, it has decreased rapidly, decreasing by approximately 80% in the past four decades, while the age-adjusted stroke mortality rate has also decreased worldwide in the past two decades [1-3]. Of all strokes, subarachnoid hemorrhage (SAH) is unique in that it develops in younger age groups, and the functional prognosis tends to be worse compared with ischemic stroke and intracerebral hemorrhage [4,5]. Despite advances in diagnostic and treatment strategies, and the gradual improvement of the fatality rate, SAH still exacts high economic and social costs [4,5]. It is well known that Finland and Japan have high incidence rates of SAH compared to the rest of the world [5]. This study aimed to evaluate the incidence rate of SAH in Japan using data from a large-scale, population-based stroke registry in Shiga Prefecture, Japan, between 2011 and 2015.

The design and information regarding the Shiga Stroke and Heart Attack Registry (SSHR) has previously been described [6]. In summary, it is an ongoing population-based registry that covers approximately 1.4 million residents of Shiga Prefecture in Japan and all cases of acute stroke that occur within that population. SSHR uses central-local coordination and monitoring, combined with remote data collection and quality control systems to create an integrated surveillance system that involves the registration of cases among a network of all acute-care hospitals with neurology and neurosurgery facilities in Shiga Prefecture. All stroke cases from January 1, 2011, to December 31, 2015, were included, and a total of 1,056 first-ever patients with SAH who were residents of Shiga Prefecture were included in the final analyses. The determination of stroke, patients’ variables, and statistical analyses are shown in the Supplementary Methods [7,8]. The age- and sex-standardized incidence rates were also calculated using the direct method with the population of the 2015 Japanese vital statistics as a reference [8].

The SSHR has been approved by the Institutional Review Board of Shiga University of Medical Science (Reference number: 23-186-1) and is in accordance with the Declaration of Helsinki and the ethical standards of the responsible committee on human experimentation. Written informed consent of participants was waived due to the nature of this study.

Table 1 shows the annual distribution of patients with SAH. A total of 1,056 patients had first-ever SAH. Women were affected approximately twice as often as men for the 5-year period. The baseline characteristics of 1,056 patients are presented in Table 2. The mean age (±standard deviation) at the time of hemorrhage was 66±15 years. Regardless of sex, the worst grade (World Federation of Neurosurgical Societies [WFNS] grade=V) was observed most frequently (36.7%), followed by the mildest grade (WFNS grade=I) (28.1%). More than 80% of the patients were transported to the hospital by ambulance and hypertension was found in 55.7% of all patients. Current smokers accounted for 49.0% of men and 16.9% of women; current drinkers accounted for 54.6% of men and 12.8% of women, and 30.8% of all patients died in the acute stage. Table 3 shows the distribution of the patients according to sex and 10-year age band and the age- and sex-standardized incidence rates according to Japan Vital Statistics 2015. Patients with SAH were most often identified in the 70s age group (22.7%), followed by the 60s age group (22.6%). The age- and sex-standardized SAH incidence rate, with the population of the 2015 Japanese vital statistics as a reference, was 10.4 per 100,000 person-years (95% confidence interval [CI], 10.2 to 10.7) in men and 22.4 per 100,000 person-years (95% CI, 22.0 ro 22.8) in women.

The number of patients with subarachnoid hemorrhage (n=1,056): The Shiga Stroke and Heart Attack Registry, Shiga, Japan, 2011–2015

Baseline characteristics of patients with subarachnoid hemorrhage stratified by sex (n=1,056): The Shiga Stroke and Heart Attack Registry, Shiga, Japan, 2011–2015

Age- and sex-specific incidence rates of subarachnoid hemorrhage per 100,000 person-years in the Shiga Stroke and Heart Attack Registry, Shiga, Japan, 2011–2015

To the best of our knowledge, these data provide an initial estimate of the overall impact of SAH and the incidence data derived from the Japanese prefectural complete enumeration registry in the 2010s for several years, where the burden of stroke has been generally higher than that of coronary heart disease [1]. The strength of this study is that a comprehensive case ascertainment protocol was used to identify non-fatal or non-hospitalized stroke cases. Determining this in a relatively large multicenter database sheds light on important aspects of patient care and can guide future research and funding. Recently, a meta-analysis showed that while worldwide SAH incidence has decreased by 40% between 1980 and 2010, SAH incidence has conversely increased by 59.1% over the last three decades in Japan [9]. In this study, the age- and sex-adjusted SAH incidence was 16.6 per 100,000 person-years (95% CI, 16.4 to 16.8), and these figures remained high compared with other countries, but were lower compared with previous Japanese registry studies; however, there are large differences in population distribution, climate, and the prevalence of risk factors between regions in Japan [8,9]. As mentioned in the meta-analysis, compared with men aged 45 to 54 years from the same region, Japanese women aged >75 years had a higher risk ratio than European women aged >75 years, and there were 362 patients (50.1%) among women aged >70 years in this study [9]. Hypothetically, this could be a consequence of the distinctly higher share of people aged ≥65 years within the total population in Japan compared with other countries; addressing the threat posed by the declining birthrate and aging population is an urgent priority for Japan, and is a challenge that has never been faced before in the world [10]. It must also be noted that most of the figures compared in the meta-analysis were obtained from hospital-based studies. Taken together, these factors suggest that further cooperation between regions and countries is desirable to encourage the establishment of nationwide registry systems, such as the nationwide Hospital Discharge Register and Causes of Death Register in Finland [11].

There are some limitations to this study. First, the present findings cannot be generalized to other Japanese regions, given the geographic and climatic disparities throughout the country. Second, there was no information on patients with stroke admitted to hospitals outside of Shiga Prefecture, which may have led to underestimating the SAH incidence rate.

In conclusion, the findings of this study underline that Japan has one of the highest SAH incidence rates in the world. The SAH incidence rate in Japan appears to be decreasing but remains high compared with that in other countries.

Supplementary materials

Supplementary materials related to this article can be found online at https://doi.org/10.5853/jos.2022.00087.

Supplementary Methods

Notes

Disclosure

The authors have no financial conflicts of interest.

References

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Article information Continued

Table 1.

The number of patients with subarachnoid hemorrhage (n=1,056): The Shiga Stroke and Heart Attack Registry, Shiga, Japan, 2011–2015

2011 2012 2013 2014 2015 Total
Men 64 53 69 68 80 334
Women 160 142 148 139 133 722
Total 224 195 217 207 213 1,056

Table 2.

Baseline characteristics of patients with subarachnoid hemorrhage stratified by sex (n=1,056): The Shiga Stroke and Heart Attack Registry, Shiga, Japan, 2011–2015

Variable Overall (n=1,056) Men (n=334) Women (n=722) P for trend
Age (yr) 66±15 60±15 68±15 <0.001
WFNS grade
 I 294 (28.1) 107 (32.3) 187 (26.1) 0.243
 II 160 (15.3) 46 (13.9) 114 (15.9)
 III 60 (5.7) 20 (6.0) 40 (5.6)
 IV 149 (14.2) 48 (14.5) 101 (14.1)
 V 385 (36.7) 110 (33.2) 275 (38.4)
Presentation
 Ambulance 873 (82.8) 265 (79.3) 608 (84.3) 0.150
 Walk-in 147 (13.9) 58 (17.4) 89 (12.3)
 Hospitalized 16 (1.5) 6 (1.8) 10 (1.4)
Hypertension 588 (55.7) 170 (50.9) 418 (57.9) 0.033
Systolic blood pressure (mm Hg) 161±38 (42–296) 163±37 (46–281) 160±38 (42–296) 0.133
Diastolic blood pressure (mm Hg) 90±23 (12–198) 95±24 (12–198) 87±23 (24–190) <0.001
Diabetes mellitus 239 (22.6) 85 (25.5) 154 (21.3) 0.137
History of coronary heart disease 39 (3.7) 16 (4.8) 23 (3.2) 0.199
Smoking habit
 Never 572 (62.5) 77 (26.6) 495 (79.1) <0.001
 Past 96 (10.5) 71 (24.5) 25 (4.0)
 Current 248 (27.1) 142 (49.0) 106 (16.9)
Drinking habit
 Never 560 (64.2) 94 (33.3) 466 (79.0) <0.001
 Past 9 (1.0) 5 (1.8) 4 (0.7)
 Occasional 75 (8.6) 30 (10.6) 45 (7.6)
 Current 228 (26.2) 153 (54.3) 75 (12.7)
mRS score at discharge
 0 105 (19.9) 28 (8.4) 77 (10.7) 0.092
 1 190 (18.0) 76 (22.8) 114 (15.8)
 2 95 (9.0) 34 (10.2) 61 (8.5)
 3 78 (7.4) 23 (6.9) 55 (7.6)
 4 136 (12.9) 43 (12.9) 93 (12.9)
 5 122 (11.6) 35 (10.5) 87 (12.1)
 6 325 (30.8) 92 (27.5) 233 (32.3)

Values are presented as mean±standard deviation, number (%), or mean±standard deviation (range). The P-values for the trend between variables were computed using linear regression for continuous variables or the Mantel−Haenszel test for categorical variables.

WFNS, World Federation of Neurosurgical Societies; mRS, modified Rankin Scale.

Table 3.

Age- and sex-specific incidence rates of subarachnoid hemorrhage per 100,000 person-years in the Shiga Stroke and Heart Attack Registry, Shiga, Japan, 2011–2015

Sex/Age (yr) No. of events Person-years Incidence rate 95% CI
Men
 0–19 2 722,814 0.3 0.02–0.8
 20–29 3 401,287 0.7 0.1–1.9
 30–39 24 477,953 5.0 3.2–7.3
 40–49 62 492,028 12.6 9.6–16.0
 50–59 68 412,448 16.5 12.7–20.7
 60–69 81 469,163 17.3 13.6–21.3
 70–79 63 312,726 20.1 15.4–25.5
 ≥80 31 162,383 19.1 12.8–26.6
 Total 334 3,450,802 9.7 8.6–10.8
 Adjusted (JP2015) 10.4 10.2–10.7
Women
 0–19 2 682,130 0.3 0.03–0.9
 20–29 3 363,384 0.8 0.1–2.1
 30–39 17 467,883 3.6 2.1–5.6
 40–49 68 484,487 14.0 10.8–17.6
 50–59 112 420,950 26.6 21.8–31.9
 60–69 158 484,012 32.6 27.7–38.0
 70–79 177 353,762 50.0 42.8–57.8
 ≥80 185 301,421 61.4 52.7–70.7
 Total 722 3,558,029 20.3 18.8–21.8
 Adjusted (JP2015) 22.4 22.0–22.8
Overall
 0–19 4 1,404,944 0.3 0.07–0.6
 20–29 6 764,671 0.8 0.3–1.6
 30–39 41 945,836 4.3 3.1–5.8
 40–49 130 976,515 13.3 11.1–15.8
 50–59 180 833,398 21.6 18.5–24.9
 60–69 239 953,175 25.1 21.9–28.4
 70–79 240 666,488 36.0 31.5–40.8
 ≥80 216 463,804 46.6 40.4–53.1
 Total 1,056 7,008.831 15.1 14.2–16.0
 Adjusted (JP2015) 16.6 16.4–16.8

CI, confidence interval; JP2015, the 2015 Japanese Population.