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.
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.
Disclosure
The authors have no financial conflicts of interest.
ReferencesUeshimaHSekikawaAMiuraKTurinTCTakashimaNKitaYCardiovascular disease and risk factors in Asia: a selected review200811827022709BenjaminEJBlahaMJChiuveSECushmanMDasSRDeoRHeart disease and stroke statistics-2017 update: a report from the American Heart Association2017135e146e603GBD 2016 DALYs and HALE CollaboratorsGlobal, regional, and national disability-adjusted life-years (DALYs) for 333 diseases and injuries and healthy life expectancy (HALE) for 195 countries and territories, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016201739012601344JohnstonSCSelvinSGressDRThe burden, trends, and demographics of mortality from subarachnoid hemorrhage19985014131418van GijnJKerrRSRinkelGJSubarachnoid haemorrhage2007369306318TakashimaNArimaHKitaYFujiiTTanaka-MizunoSShitaraSLong-term survival after stroke in 1.4 million Japanese population: Shiga Stroke and Heart Attack Registry202022336344ThorvaldsenPKuulasmaaKRajakangasAMRastenyteDSartiCWilhelmsenLStroke trends in the WHO MONICA project199728500506Statistics Bureau of Japan, Ministry of Health, Labour and Welfare, Japanhttps://www.stat.go.jp/english/data/kokusei/2015/summary.html. 2015. Accessed February 28, 2022.EtminanNChangHSHackenbergKde RooijNKVergouwenMDRinkelGJWorldwide incidence of aneurysmal subarachnoid hemorrhage according to region, time period, blood pressure, and smoking prevalence in the population: a systematic review and meta-analysis201976588597Cabinet Office Government of Japanhttps://www8.cao.go.jp/kourei/english/annualreport/index-wh.html. 2019. Accessed February 28, 2022.KorjaMLehtoHJuvelaSKaprioJIncidence of subarachnoid hemorrhage is decreasing together with decreasing smoking rates20168711181123Tables
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
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.
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.