Perspectives acquired through long-term epidemiological studies on the Great East Japan Earthquake
Tsuboya et al. Environmental Health and Preventive Medicine
Perspectives acquired through long-term epidemiological studies on the Great East Japan Earthquake
Toru Tsuboya 0
Mariko Inoue 0
Michihiro Satoh 0
Kei Asayama 0 1 2
0 Part of this work was presented at the 86th Annual Meeting of the Japanese Society for Hygiene (Asahikawa , Japan 2016)
1 Department of Planning for Drug Development and Clinical Evaluation, Tohoku University Graduate School of Pharmaceutical Sciences , 2-1 Seiryo-cho, Aoba-ku, Sendai 980-8575 , Japan
2 Department of Hygiene and Public Health, Teikyo University School of Medicine , Tokyo , Japan
The Great East Japan Earthquake (GEJE) and subsequent tsunamis that occurred in 2011 caused extensive and severe structural damage and interrupted numerous research activities; however, the majority of such activities have been revived, and further public health researches and activities have started to follow the population affected by the disaster. In this mini-review, we overview our recent activities regarding epidemiologic studies in Miyagi Prefecture, the region most affected by the GEJE. Through our study processes, we were able to identify the particular characteristics of vulnerable populations, and provide ideas that may help save lives and reduce the amount of damage caused by a future disaster. Long-term follow-up and care of survivors is essential in affected areas, and health professionals should pay particular attention to various diseases, e.g., cardiovascular complications and mental disorders. Furthermore, building up resilience and social relationships in the community is beneficial to survivors. Ongoing cohort studies conducted before disasters can help minimize biases regarding the survivors' pre-disaster information, and emerging cohort studies after disasters can find potential helpful novel indices. To identify characteristics of vulnerable populations, save lives, and reduce the amount of damage caused by a future disaster, constant research that is consistently improved by new data needs to be performed.
Great East Japan Earthquake; Tsunami; Cohort study; Resilience; Disaster
The Great East Japan Earthquake (GEJE) and subsequent
tsunamis occurred at 14:46 on March 11, 2011 [1, 2]. The
GEJE had a magnitude of 9.0 on the Richter scale, making
it the most powerful earthquake in Japan and the fourth
in the world since modern record-keeping began in 1900.
The GEJE triggered a series of devastating tsunamis, that
caused extensive and severe structural damage and
interrupted numerous research activities, such as ongoing
community-based cohort and epidemiological studies.
However, the majority of these research activities have
since been revived, and further public health research and
activities have started to follow the population most
affected by the GEJE. Based on the recent seismological
findings, a simple ‘characteristic earthquake’ model for
the long-term forecast is difficult to apply, e.g.,
recurrence of Nankai Trough Earthquake with an interval
of ≈ 100 years has been identified but the sizes of
recurrent earthquakes vary according to tsunami deposits
. We should therefore improve managing disaster
risks for a resilient future (https://www.gfdrr.org/sites/
gfdrr/files/sendai/sendai.html (2016.10.17)). In this
minireview, we provide a brief overview of our recent activities
based on epidemiological studies conducting in Miyagi
Prefecture , the region most affected by the disaster, and
discuss what we need for saving lives and reducing
damage after a disaster. We further aim to specify a
significance of consistent improvement of longitudinal
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Iwanuma project — social cohesion and mental
The Iwanuma Project [4, 5] is a part of the general
population-based Japan Gerontological Evaluation
Study (JAGES) [6, 7]. The JAGES was a nationwide
study established in 2010 to prospectively examine
the determinants of healthy aging . Approximately
48% of Iwanuma City, which is located in a southern
coastal area in Miyagi Prefecture, was inundated by
the tsunamis after the GEJE (Table 1). Approximately
2.5 years after the disaster, we carried out a follow-up
survey among 4,380 survivors in Iwanuma aged ≥65 years
old [4, 5].
Among the analytic sample of the Iwanuma residents,
38.0% reported losing loved ones such as friends or
relatives, 59.0% reported damage to their property
resulting from the GEJE, and 11.4% reported having
symptoms of severe posttraumatic stress disorder, 
which was measured using the Screening Questionnaire
for Disaster-Related Mental Health . Based on the
spatial Durbin model, which can capture the spatial
spillover association of community social cohesion, 
social cohesion was significantly associated with a risk
of posttraumatic stress disorder symptoms at both the
individual-level (odds ratio [OR], 0.87; 95% confidence
interval [CI], 0.77–0.98) and community-level (OR, 0.75;
95% CI, 0.63–0.90) . Loss of loved ones and damaged
housing at the individual level and an interruption in
access to internal medicine and psychiatry services were
also associated with a higher risk of posttraumatic stress
disorder symptoms (p < 0.01) . We would emphasize
that our findings were not affected by recall bias because
we obtained information on Iwanuma residents both
before and after the GEJE. Social cohesion among neighbors
may help to explain the community-level variations in the
occurrence of posttraumatic stress disorder after natural
We further found associations between experiences of
disaster-related damage and changes in depressive
symptoms among survivors,  based on the dichotomous
15items Geriatric Depression Scale (GDS), which has been
validated in both English  and Japanese . We
evaluated personal experiences of damage caused by the GEJE
and tsunamis based on previous studies on mental health
among survivors after natural disasters, in consideration
of the local culture [11, 12]. Among 3,464 eligible
participants with complete data, the mean (SD) GDS scores at
baseline and follow-up were 3.74 (3.5) and 3.84 (3.4),
respectively. The changes in GDS scores between the
two surveys were more pronounced among men than
among women (0.17 versus 0.05).
Multivariateadjusted linear regression analysis showed that
experiences of property loss were significantly associated
with worsening GDS scores: the non-standardized
coefficient of the model was 1.40 (95% CI, 0.96–1.83)
for total housing loss and 0.47 (95% CI, 0.21–0.74)
for loss of an automobile. The impact on loss of
family members was also significant, whereas the effect
size of the GDS was relatively small, at 0.23 (95% CI,
0.02–0.44). Both loss of employment (n = 186, 5.1%)
Table 1 Population sampling methods and characteristics of each study
Iwanuma Projecta [4, 5] Health and Life Revival Council
in Ishinomaki District (RCI)
[13, 14, 16–18]
Place of municipality Iwanuma Ishinomaki
Damage from GEJE and subsequent 187 died, 48% of the land 3,055 died, 420 missing, 270 certified
tsunamis on Mar 2011 was inundated. as disaster-related death.
On TSCD, 2 mothers and 3 children died, 10
families missing, the investigation was
suspended for 5 months.
8,576 residents ≥65 years ≈8,700 survivor families living only on Neonates born at 36–42 weeks of gestation
the 2nd floor of their damaged houses with a birth weight of ≥2400 g.
Oct 2013 to Jan 2014
mental health, physical
function, social activies
Jan 2001 to Sep 2005
Mar 2013 as the 7-year-old survey
n/a (2 surveys not yet fully linked)
Sleep problems, psychological distress, Home and conventional blood pressure, verbal,
symptoms, access to health services performance, and full-scale IQ, autonomic
GEJE the Great East Japan Earthquake, PTSD posttraumatic stress disorder, IQ intelligence quotient
aIwanuma Project is a part of the Japan Gerontological Evaluation Study
and disruption of access to psychiatric care (n = 17,
0.5%) were also associated with worsening GDS scores
(p < 0.0001). In a community-dwelling elderly
population, loss of employment, disruption of access to
psychiatric care, and personal experiences of property damage
predict a worsening of depressive symptoms, and have a
more pronounced and lingering impact compared with
experiencing the loss of a loved one .
Health and life revival council in Ishinomaki
District — community support
Ishinomaki is one of the municipalities most severely
damaged from the GEJE and subsequent tsunamis
(Table 1) [13, 14]. After the GEJE, approximately 8,700
families in Ishinomaki remained at home, despite serious
structural damage; many of these residents were living
entirely on the second floor of their homes because the
tsunami had completely swept away everything on the
first floor [13, 14]. This vulnerable population, referred
to as the stay-at-home victims, was provided with less
support by governmental agencies than those living in
temporary shelters. To identify and evaluate stay-at-home
survivors for providing more rapid and appropriate
support in response to their needs, the Health and Life
Revival Council in Ishinomaki District (RCI) conducted a
face-to-face survey. We used a semi-structured
questionnaire composed of the following three sections: household
demographics; social background; and health condition of
individuals most in need of medical support. The
firstterm survey was started approximately 6 to 12 months
after the GEDE (Table 1) .
Initially, data from 4,176 households were analyzed, with
4,023 household members agreeing to be interviewed
using the written form in the first-term and future surveys
. Factors associated with sleep difficulties which
frequently begin as stress-related phenomena including
natural disaster  were loss of pleasure in life (OR, 1.37;
95% CI, 1.07–1.76), living on a pension (versus living on
salary: OR, 1.58; 95% CI, 1.09–2.27) or public livelihood
assistance (versus living on salary: OR, 4.40; 95% CI,
1.53–12.65), or women (OR, 2.67; 95% CI, 2.07–3.46)
. Interacting with neighbors by visiting one another
was positively associated with sleep (OR, 0.42; 95% CI,
0.24–0.74) . Among survivors living at home
around 2 years after the GEJE, participants with
emotional social support (OR, 2.05; 95% CI, 1.35–3.11) and
informational social support (OR, 1.55; 95% CI, 1.08–
2.21) had lower rates of sleep difficulties, 
suggesting that relatively strong neighborhood networks help
prevent sleep difficulties. Loss of pleasure in life (OR,
1.25; 95% CI, 1.00–1.57), changes in family structure
(OR, 1.46; 95% CI, 1.15–1.85), and changes in work
status (OR, 1.30; 95% CI, 1.06–1.59) were also
significant factors associated with psychological distress .
Contrary to the hypothesis, the elderly (>65 years) were
more likely to have close neighbors and social/family
interactions; non-elderly men living alone represented
the highest proportion of people without social/family
interactions, and persons living alone were less likely to
have social/family interactions . Strengthening social
ties before and after disasters is important in building a
resilient community capable of supporting the physical and
mental health of its citizens.
The Tohoku study of child development —
comprehensive development of children
The Tohoku Study of Child Development (TSCD) is a
prospective birth cohort study primarily carried out to
investigate the potential effects of perinatal exposure to
environmental pollutants on the neurobehavioral
development of children (Table 1) [19, 20]. After conducting
periodic surveys, self-measured home blood pressure of
children at 7 years of age was recorded; however, the
GEJE caused a disruption in the data collection among
those in the affected rural coastal areas [2, 21]. Although
several participants were victimized (Table 1),  further
research equipment, such as home blood pressure devices,
were supplied relatively quickly, and data were recovered
from a backup system as well as from the internal storage
of each device, and the examinations were successfully
resumed 5 months after the GEJE .
Maternal gestational hypertension did not affect home
blood pressure in offspring, but it did strongly affect
maternal home blood pressure, even 7 years after giving
birth . Home blood pressure among children with
7 years of age who received long-term (mean, 11.3 months)
breastfeeding as a major source of nutrition was
significantly lower than that among children who received
short-term (mean, 5.1 months) breastfeeding (92.9/55.1
versus 94.7/56.4 mm Hg systolic/diastolic blood pressure,
respectively; p = 0.006/0.04), suggesting that long-term
breastfeeding had a protective effect against elevated
blood pressure even in young children .
Furthermore, Tatsuta and colleauges assessed the
neurodevelopmental effects of the GEJE . Verbal intelligence
quotient (IQ) at 7 years of age was significantly lower
in a post-disaster group than in a pre-disaster group
after the adjustment of preceding neurodevelopmental
scores taken at 32 and 40 month olds (p = 0.001). In
contrast, no significant differences were found in
performance IQ, full-scale IQ, or autonomic nervous indicators
(p = 0.053). This finding implies the indispensable effect
of interrupted schooling .
The TSCD offered the opportunity to start a new line
of longitudinal research into cardiovascular risk factors,
such as blood pressures, as measured by conventional
and self-measured at home in children from childhood
to adolescence along with their mothers . The TSCD
is currently investigating the comprehensive health and
development of children, including the long-term
multilateral impact of the inevitable effects of the disaster .
Other studies in Miyagi Prefecture —
hypertension and diabetes
Our research group has engaged in other collaborative
research projects, such as local hospital-based surveys.
Satoh and coworkers compared home blood pressure
just before and after the GEJE in 142 hypertensive
patients (40.8% women; mean age, 68.1 years) . The
mean home systolic blood pressure of 126.9 mm Hg just
before the GEJE increased to 129.3 mm Hg just after
the GEJE. This increase remained significant 2 weeks
after (p = 0.03) but disappeared by 4 weeks after the
GEJE (p = 0.2). Among the 142 hypertensive patients,
only 10 could measure their home blood pressure in
the morning before the GEJE and during the
subsequent 3 days after the GEJE. A steep elevation in home
blood pressure was observed in those 10 patients, with
the difference of 11.6 mm Hg in home systolic blood
pressure between the day of and the day after the GEJE
(p = 0.02) .
Tanaka and colleagues investigated the impact of the
GEJE on glycemic control based on 497 diabetic patients
who had been followed at hospitals in the devastated
Tohoku area . Notably, the HbA1c levels of the
diabetic patients were not elevated at 1 month after, and
were significantly decreased at 3 months after as
compared with before the GEJE . This might have been
the result of weight loss due to energy restrictions.
Meanwhile, impaired endogenous insulin secretory
capacity was associated with worsening of glycemic control
after the GEJE . The increased blood pressure or
worsening of glycemic control might have led to an
increase in the risk of cardiovascular disease just after
the disaster [27, 28].
However, these studies [24–26] were only based on
participants who could measure their blood pressure at home
or visit clinics immediately after the GEJE. Survivors after
a disaster would be expected to have higher cardiovascular
risk because they cannot afford to take care of their health
due to the loss of their home or loved ones. However,
there are limitations in investigating the precise effects of
a disaster on such survivors unless pre-disaster health data
are available. For the management of hypertension in
disaster conditions, a special network system for supporting
continuous self-measurement of home blood pressure has
been proposed . Although it is impossible to monitor
everyone after a large-scale disaster, daily home blood
pressure measurement among survivors would be useful
for investigating the effects of a disaster in relation to
cardiovascular complications [24, 29].
We reviewed several studies in which we have taken
part in on social, [4–6, 13, 14, 16–18] birth, [2, 19–23]
and cardiovascular [21–27] epidemiologies regarding
the GEJE. Through these study processes, we could
help identify same particular characteristics of
vulnerable populations and provide further ideas for saving
lives and reducing damage after future disasters, e.g., by
building social capital or social networks within
communities. To ensure the ability to respond to such a
disaster promptly, our findings can also assist in
building a model for collaboration between academic
institutions and non-governmental as well as governmental
organizations. Both long-term follow-up and care of
survivors in the affected areas are essential, and health
professionals should pay special attention to various
diseases such as cardiovascular complications and
mental disorders. Besides providing sufficient medical care,
building up resilience and social relationships in the
community is expected to be beneficial to survivors.
Ongoing cohort studies before disasters [2, 4–6, 19–23]
can minimize biases regarding pre-disaster information
for survivors, whereas emerging cohort studies after
disasters [13, 14, 16–18, 24–27] can identify potentially
useful novel indices. Constant research that is consistently
improved by new data, therefore, needs to be performed.
We would like to express our gratitude to all the staff members of the
Iwanuma Project, the Health and Life Revival Council in Ishinomaki District,
and the Tohoku Study of Child Development for their valuable contributions
in relation to data collection and database management. We also wish to
thank all of the participants in these studies.
The JAGES project was supported by the NIH (R01 AG042463); Grant-in-Aid for
Scientific Research (23243070, 22390400, 24390469) from the Japanese Ministry
of Education, Culture, Sports, Science and Technology (MEXT); Health Labour
Sciences Research Grant (H24-Choju-Wakate-009); the Center for Wellbeing
and Society, Nihon Fukushi University; and MEXT-Supported Program for
the Strategic Research Foundation at Private Universities.
Teikyo University Graduate School of Public Health was supported by the
Japan Public Health Society through a Special Grant for public health in the
Great East Japan Earthquake in 2012.
The Tohoku Study of Child Development was supported by Grants for
Scientific Research (23390171) from MEXT, Japan; a Grant-in-Aid for Japan
Society for the Promotion of Science (JSPS) fellows (25*7756 and 25*9328);
the Ministry of Health, Labour and Welfare, Japan; the Ministry of the
Environment, Japan; and the Grant for Environmental Research Projects
from the Sumitomo Foundation.
KA received the 2015 Japanese Society for Hygiene research grant for
young investigators’ project on behalf of all coauthors. All funding
sources did not have any role in the design and conduct of the study,
the collection, management, analysis, or interpretation of the data, the
preparation, review, or approval of the manuscript, or the decision to
submit the manuscript.
KA conceived and designed this review. TT, MI, KA, and MS contributed to
the design and to the collection and interpretation of the data in Iwanuma
project, the RCI, the TSCD, and other studies in Miyagi Prefecture,
respectively. TT and KA wrote the first draft of the review. All authors made
critical revision of the manuscript for important intellectual content.
All authors read and approved the final manuscript.
1. Ishigaki A , Higashi H , Sakamoto T , Shibahara S. The Great East-Japan Earthquake and devastating tsunami: an update and lessons from the past Great Earthquakes in Japan since 1923 . Tohoku J Exp Med . 2013 ; 229 : 287 - 99 .
2. Tatsuta N , Nakai K , Satoh H , Murata K. Impact of the Great East Japan Earthquake on Child's IQ. J Pediatr . 2015 ; 167 : 745 - 51 .
3. Satake K. Geological and historical evidence of irregular recurrent earthquakes in Japan . Philos Trans A Math Phys Eng Sci . 2015 ;373. doi:10. 1098/rsta.2014.0375.
4. Hikichi H , Aida J , Tsuboya T , Kondo K , Kawachi I. Can Community Social Cohesion Prevent Posttraumatic Stress Disorder in the Aftermath of a Disaster? A Natural Experiment From the 2011 Tohoku Earthquake and Tsunami . Am J Epidemiol . 2016 ; 183 : 902 - 10 .
5. Tsuboya T , Aida J , Hikichi H , Subramanian SV , Kondo K , Osaka K , et al. Predictors of depressive symptoms following the Great East Japan earthquake: A prospective study . Soc Sci Med . 2016 ; 161 : 47 - 54 .
6. Fujiwara T , Kondo K , Shirai K , Suzuki K , Kawachi I. Associations of childhood socioeconomic status and adulthood height with functional limitations among Japanese older people: results from the JAGES 2010 Project . J Gerontol A Biol Sci Med Sci . 2014 ; 69 : 852 - 9 .
7. Saito M , Kondo K , Kondo N , Abe A , Ojima T , Suzuki K , et al. Relative deprivation, poverty, and subjective health: JAGES cross-sectional study . PloS one . 2014 ; 9 : e111169 .
8. Fujii S , Kato H , Maeda K. A simple interview-format screening measure for disaster mental health: an instrument newly developed after the 1995 Great Hanshin Earthquake in Japan-the Screening Questionnaire for Disaster Mental Health (SQD) . Kobe J Med Sci . 2007 ; 53 : 375 - 85 .
9. Elhorst JP . Applied spatial econometrics: raising the bar . Spat Econ Anal . 2010 ; 5 : 9 - 28 .
10. Yesavage JA , Brink TL , Rose TL , Lum O , Huang V , Adey M , et al. Development and validation of a geriatric depression screening scale: a preliminary report . J Psychiatr Res . 1982 ; 17 : 37 - 49 .
11. van Griensven F , Chakkraband ML , Thienkrua W , Pengjuntr W , Lopes Cardozo B , Tantipiwatanaskul P , et al. Mental health problems among adults in tsunami-affected areas in southern Thailand . JAMA. 2006 ; 296 : 537 - 48 .
12. Frankenberg E , Friedman J , Gillespie T , Ingwersen N , Pynoos R , Rifai IU , et al. Mental health in Sumatra after the tsunami . Am J Public Health . 2008 ; 98 : 1671 - 7 .
13. Ishiguro A , Togita Y , Inoue M , Ohkubo T , Yano E. Identification of disastervulnerable communities by use of census data prior to the Great East Japan Earthquake . Disaster Med Public Health Prep . 2015 ; 9 : 19 - 28 .
14. Matsumoto S , Yamaoka K , Inoue M , Muto S , Teikyo Ishinomaki Research Group, Health, Life Revival Council in the Ishinomaki district . Social ties may play a critical role in mitigating sleep difficulties in disaster-affected communities: a cross-sectional study in the Ishinomaki area , Japan. Sleep . 2014 ; 37 : 137 - 45 .
15. Davidson LM , Fleming R , Baum A. Chronic stress, catecholamines, and sleep disturbance at Three Mile Island . J Human Stress . 1987 ; 13 : 75 - 83 .
16. Matsumoto S , Yamaoka K , Inoue M , Inoue M , Muto S , Teikyo Ishinomaki Research Group. Implications for Social Support on Prolonged Sleep Difficulties among a Disaster-Affected Population: Second Report from a Cross-Sectional Survey in Ishinomaki, Japan . PloS One . 2015 ; 10 :e0130615.
17. Furukawa H , Takeuchi T , Yano E , Muto S. Factors influencing psychological distress after the Great East Japan Earthquake and Tsunami . J Community Psychol . 2015 ; 43 : 521 - 6 .
18. Inoue M , Matsumoto S , Yamaoka K , Muto S. Risk of social isolation among Great East Japan Earthquake survivors living in tsunami-affected Ishinomaki , Japan. Disaster Med Public Health Prep . 2014 ; 8 : 333 - 40 .
19. Suzuki K , Nakai K , Sugawara T , Nakamura T , Ohba T , Shimada M , et al. Neurobehavioral effects of prenatal exposure to methylmercury and PCBs, and seafood intake: neonatal behavioral assessment scale results of Tohoku study of child development . Environ Res . 2010 ; 110 : 699 - 704 .
20. Nakai K , Suzuki K , Oka T , Murata K , Sakamoto M , Okamura K , et al. The Tohoku Study of Child Development: A cohort study of effects of perinatal exposures to methylmercury and environmentally persistent organic pollutants on neurobehavioral development in Japanese children . Tohoku J Exp Med . 2004 ; 202 : 227 - 37 .
21. Asayama K , Staessen JA , Hayashi K , Hosaka M , Tatsuta N , Kurokawa N , et al. Mother-offspring aggregation in home versus conventional blood pressure in the Tohoku Study of Child Development (TSCD) . Acta Cardiol . 2012 ; 67 : 449 - 56 .
22. Hosaka M , Asayama K , Staessen JA , Tatsuta N , Satoh M , Kikuya M , et al. Relationship between maternal gestational hypertension and home blood pressure in 7-year-old children and their mothers: Tohoku Study of Child Development . Hypertens Res . 2015 ; 38 : 776 - 82 .
23. Hosaka M , Asayama K , Staessen JA , Ohkubo T , Hayashi K , Tatsuta N , et al. Breastfeeding leads to lower blood pressure in 7-year-old Japanese children: Tohoku Study of Child Development . Hypertens Res . 2013 ; 36 : 117 - 22 .
24. Satoh M , Kikuya M , Ohkubo T , Imai Y. Acute and subacute effects of the great East Japan earthquake on home blood pressure values . Hypertension . 2011 ; 58 : e193 - 4 .
25. Tanaka M , Imai J , Satoh M , Hashimoto T , Izumi T , Sawada S , et al. Impacts of the Great East Japan Earthquake on diabetic patients. J Diabetes Investig . 2015 ; 6 : 577 - 86 .
26. Tanaka M , Imai J , Satoh M , Hashimoto T , Izumi T , Sawada S , et al. Glycemic control in diabetic patients with impaired endogenous insulin secretory capacity is vulnerable after a natural disaster: study of Great East Japan Earthquake . Diabetes Care . 2014 ; 37 : e212 - 3 .
27. Aoki T , Fukumoto Y , Yasuda S , Sakata Y , Ito K , Takahashi J , et al. The Great East Japan Earthquake Disaster and cardiovascular diseases . Eur Heart J . 2012 ; 33 : 2796 - 803 .
28. Nishizawa M , Hoshide S , Shimpo M , Kario K. Disaster hypertension: experience from the great East Japan earthquake of 2011 . Curr Hypertens Rep . 2012 ; 14 : 375 - 81 .
29. Imai Y , Kario K , Shimada K , Kawano Y , Hasebe N , Matsuura H , et al. The Japanese Society of Hypertension Guidelines for Self-monitoring of Blood Pressure at Home (Second Edition) . Hypertens Res . 2012 ; 35 : 777 - 95 .