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Li et al.
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Figure 1. Sex-specific, age-standardized incidence ratios (95% confidence intervals) of all strokes in rural versus urban residents
aged ⩾40 years during the seven survey periods.
Men
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Women
the Hisayama study decreased substantially from 1961-
1968 to 1974-1981, then decreased with a slowdown from
1974-1981 to 2002-2009.11 Slow decreasing trends from
the 1980s was also reported in a stroke registry study.13
To the best of our knowledge, the CIRCS, including the
previous reports2,7 and this update, is the only Japanese
study that could compare the long-term stroke trends based
on unified surveillance systems between the urban and
rural communities. At the beginning of the CIRCS survey,
the rural community (Ikawa town, Akita Prefecture) had
the highest stroke mortality in both Japan and the world,
and the urban community (Yao City, Osaka Prefecture) had
lower stroke mortality in Japan,2 so that obvious urban-
rural disparities of stroke incidence were observed in the
1960s. As a result of positive and targeted cardiovascular
preventive measures in the urban and rural communities, a
decreased trend was observed over the past half century.
The incidence of all strokes in the period of 2012-2018 in
our data was 1.15 (0.86-1.44) per 1000/year for men and
0.59 (0.39-0.79) for women in the urban community, and
1.98 (1.20-2.77) and 1.31 (0.67-1.94) in the rural community,
respectively, which were close to the 2019 global incidence
of 1.51 (1.37-1.68) and 1.50 (1.36-1.67) for women
except for urban women, whereas the incidence in Japan
remained higher than that in many Western countries
including the United States, the United Kingdom, and
France.1,14 Furthermore, this decreased trend slowed down
since the 1980s, and the urban-rural disparities remain
apparent more recently.
The strengths of our study lie in comparing stroke incidence
in two communities under continued cardiovascular
prevention programs. These prevention programs were formulated
according
to
community
circumstances
and
improved
with time. For example, a prior CIRCS report
showed that our rural hypertension control program, containing
intensive, accessible, community-based interventions
and health education, was associated with effectively
prevented incident stroke in rural men.15 Accordingly, the
stroke burden switched from severe/moderate to mild
hypertension between 1963 and 1997.16 We used consistently
the clinical criteria for the diagnosis of all strokes,
which was barely changed over time, throughout the whole
study period for the primary analysis of trends in all strokes.
The limitations of this study are noteworthy. First, trends
for the incidence of ischemic stroke subtypes were not well
explored because of the small number of cases, the improvements
in CT/MRI techniques over time, and difficulty in
distinguishing subtypes between large-artery occlusive and
embolic infarctions. Second, the number of enrolled communities
was small, and hence it restricted the generalization
power to other Japanese communities.
In conclusion, Japan had a very high stroke incidence
among the world in the 1960s, followed by substantial
decreasing trends in both urban and rural Japanese communities,
albeit a higher incidence in the rural than in the
urban communities. The stroke incidence in Japanese communities
remained higher than that in many Western countries.
These findings suggest the necessity of continued
public health efforts to reduce stroke incidence in Japan.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with
respect to the research, authorship, and/or publication of this
article.
Funding
The author(s) disclosed receipt of the following financial support
for the research, authorship, and/or publication of this article: This
study was supported by a Grant-in-Aid for Scientific Research A
(grant number 04304036), Scientific Research B (grant numbers
60480184 and 02454209), Scientific Research C (grant numbers
15K08806 and 24590792) from the Japan Society for the
Promotion of Science.
ORCID iD
Hiroyasu Iso
https://orcid.org/0000-0002-9241-7289
International Journal of Stroke, 18(6)
1963/64-1971
1972-1979
1980-1987
1988-1995
1996-2003
2004-2011
2012-2018
1963/64-1971
1972-1979
1980-1987
1988-1995
1996-2003
2004-2011
2012-2018
Incidence ratio
https://www.orcid.org/0000-0002-9241-7289
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