Causal Inference in Studying the Long-Term Health Effects of Disasters: Challenges and Potential Solutions.

Two frequently encountered but underrecognized challenges for causal inference in studying the long-term health effects of disasters among survivors include 1) time-varying effects of disasters on a time-to-event outcome and 2) selection bias due to selective attrition. In this paper, we review approaches for overcoming these challenges and demonstrate application of the approaches to a real-world longitudinal data set of older adults who were directly affected by the 2011 Great East Japan Earthquake and Tsunami (n = 4,857). To illustrate the problem of time-varying effects of disasters, we examined the association between degree of damage due to the tsunami and all-cause mortality. We compared results from Cox regression analysis assuming proportional hazards with those derived using adjusted parametric survival curves allowing for time-varying hazard ratios. To illustrate the problem of selection bias, we examined the association between proximity to the coast (a proxy for housing damage from the tsunami) and depressive symptoms. We corrected for selection bias due to attrition in the 2 postdisaster follow-up surveys (conducted in 2013 and 2016) using multivariable adjustment, inverse probability of censoring weighting, and survivor average causal effect estimation. Our results demonstrate that analytical approaches which ignore time-varying effects on mortality and selection bias due to selective attrition may underestimate the long-term health effects of disasters.

Evacuees and Migrants Exhibit Different Migration Systems After the Great East Japan Earthquake and Tsunami.

Research on the destinations of environmentally induced migrants has found simultaneous migration to both nearby and long-distance destinations, most likely caused by the comingling of evacuee and permanent migrant data. Using a unique data set of separate evacuee and migration destinations, we compare and contrast the pre-, peri-, and post-disaster migration systems of permanent migrants and temporary evacuees of the Great East Japan Earthquake and Tsunami. We construct and compare prefecture-to-prefecture migration matrices for Japanese prefectures to investigate the similarity of migration systems. We find evidence supporting the presence of two separate migration systems-one for evacuees, who seem to emphasize short distance migration, and one for more permanent migrants, who emphasize migration to destinations with preexisting ties. Additionally, our results show that permanent migration in the peri- and post-periods is largely identical to the preexisting migration system. Our results demonstrate stability in migration systems concerning migration after a major environmental event.

Effect of seawalls on tsunami evacuation departure in the 2011 Great East Japan Earthquake.

OBJECTIVE: To quantitatively evaluate the effect of seawalls on tsunami evacuation departure. METHODS: A mixed-effect Cox proportional-hazards regression model was applied to evacuation behavioural data obtained from a probability survey of survivors of the 2011 Great East Japan Earthquake and Tsunami in Iwate and Miyagi prefectures. FINDINGS: Presence of a seawall higher than the forecast tsunami height at any given time reduces the likelihood of prompt evacuation by 30%. Findings suggest the existence of a false sense of security among residents deriving from the presence of seawalls. CONCLUSION: Prompt evacuation is a key factor affecting survival. The effect of seawalls on evacuation decisions is an important policy consideration. More work is needed in disaster preparedness education and in the way tsunami warnings are given, taking into consideration the risk of forecast error. Priority should be given to promoting prompt evacuation and educating residents as to the uncertainty of tsunami forecasting, to ensure that residents do not ignore evacuation warnings due to false impressions of the safety provided by seawalls.

Potential tsunami risk assessment to the city of Alexandria, Egypt.

Tsunami extreme events present a highly significant hazard and considerable risk to the coastal communities. The continued occurrence of tsunami incidents, together with population growth, increases the risk in coastal communities. Two known catastrophic historic tsunamis in Alexandria occurred in the years 365 and 1303 AD, with reported wave heights of 1 m and 2.9 m, respectively. Approximately 5000 people lost their lives and 50,000 homes were destroyed in the city after the earthquake in 365. The 1303 tsunami destroyed the great lighthouse of Alexandria, one of the seven wonders of the ancient world. In order to avoid such events in the future, a detailed knowledge about the tsunami phenomenon and its potential risk is needed. In this paper, the vulnerability and risk to the city of Alexandria will be examined by remote sensing and GIS techniques considering three scenarios. Methodology used depends on building a comprehensive GIS in addition to recent satellite images. After digitizing raster data, it was then stored into a vector format. A digital parcel map was created; attributes (like distance to shore line, elevation, land use/cover, and population) for each polygon were added. Using the Shuttle Radar Topography Mission images, a digital elevation model was created, to test all the tsunami scenarios (based on 5 m, 9 m, and 20 m wave's height). Finally, vulnerability analysis including physical as well as social and economic constraints was executed for the determination of the vulnerability level of elements. Results indicated that Alexandria city is highly vulnerable to tsunami hazard. Very high risk covers the biggest portion of the area in Alexandria (49.16% and 58.71%), followed by high risk (30% and 28.41%), medium risk (13.61% and 7.76%), and low and very low risk (20.82% and 12.88%).

Factors associated with social support in child-rearing among mothers in post-disaster communities.

BACKGROUND: Natural disasters have long-term negative impacts on the health and socioenvironmental conditions of a population, affecting the physical environment as well as the relationships within the community, including social networks. Mothers in post-disaster communities may have difficulty receiving social support not only from family members and relatives but also from members of their community, such as people in their neighborhoods. This study focused on mothers with infants and preschool-aged children in post-disaster communities. The associations of social support with sociodemographic characteristics and socioenvironmental conditions related to child-rearing among mothers in post-disaster communities were assessed. METHODS: An anonymous self-administered questionnaire survey was conducted in October 2015 in 988 households in areas affected by the Great East Japan Earthquake and Tsunami. The data collected on sociodemographic and socioenvironmental characteristics included the presence of pre-disaster acquaintances in the neighborhood and social support for child-rearing. The associations of sociodemographic and socioenvironmental characteristics with social support were examined. RESULTS: We analyzed 215 completed questionnaires from mothers living in different houses from those they lived in before the disaster to reflect continuous relationships with people from the pre-disaster communities. Social support was significantly associated with infant sex, extended family, support obtained from relatives not living together, pre-disaster acquaintances, use of child support resources, and no perceived difficulties in child-rearing. In addition, the presence of pre-disaster acquaintances was associated with categories of mental/physical place of comfort and child-rearing support, with adjusted odds ratios of 1.88 (95% CI 1.03-3.44) and 2.84 (95% CI 1.46-5.52) compared with mothers who did not have any pre-disaster acquaintances. CONCLUSIONS: Factors associated with the obtainment of social support in child-rearing among mothers in post-disaster communities were attributed not only to mothers themselves and family members but also to socioenvironmental factors such as the presence of pre-disaster acquaintances. The presence of pre-disaster acquaintances promoted rich social support in child-rearing in post-disaster communities. When reconstructing a community following changes in residence location after a disaster, the pre-disaster relationships among the community dwellers should be considered from the viewpoint of child-rearing support.

Can Community Social Cohesion Prevent Posttraumatic Stress Disorder in the Aftermath of a Disaster? A Natural Experiment From the 2011 Tohoku Earthquake and Tsunami.

In the aftermath of a disaster, the risk of posttraumatic stress disorder (PTSD) is high. We sought to examine whether the predisaster level of community social cohesion was associated with a lower risk of PTSD after the earthquake and tsunami in Tohoku, Japan, on March 11, 2011. The baseline for our natural experiment was established in a survey of older community-dwelling adults who lived 80 kilometers west of the epicenter 7 months before the earthquake and tsunami. A follow-up survey was conducted approximately 2.5 years after the disaster. We used a spatial Durbin model to examine the association of community-level social cohesion with the individual risk of PTSD. Among our analytic sample (n = 3,567), 11.4% of respondents reported severe PTSD symptoms. In the spatial Durbin model, individual- and community-level social cohesion before the disaster were significantly associated with lower risks of PTSD symptoms (odds ratio = 0.87, 95% confidence interval: 0.77, 0.98 and odds ratio = 0.75, 95% confidence interval: 0.63, 0.90, respectively), even after adjustment for depression symptoms at baseline and experiences during the disaster (including loss of loved ones, housing damage, and interruption of access to health care). Community-level social cohesion strengthens the resilience of community residents in the aftermath of a disaster.

Prospect of future housing and risk of psychological distress at 1 year after an earthquake disaster.

AIM: Since the Great East Japan Earthquake in 2011, many of the affected have been forced to live in temporary housing or at a relative's house. Special attention needs to be paid to the negative health impacts resulting from such changes in living conditions. This study examined the association between future housing prospects and the risk of psychological distress 1 year after the earthquake. METHODS: In 2012, a questionnaire was completed by a cross-sectional study of people aged 20 years or older living in Shichigahama Town, Miyagi, northeastern Japan, an area that had been severely inundated by the tsunami. Future housing prospects post-earthquake were classified into four categories: already settled in permanent housing, moving to new housing, under consideration, or unable to make any plans. Psychological distress was evaluated using the Kessler 6 scale, defined as ≥5 points out of 24. We performed multiple logistic regression analyses adjusted for potential confounding factors. RESULTS: Of the 3614 individuals studied, subjects whose future housing was under consideration (odds ratio [OR] = 2.1, 95% confidence interval [CI] = 1.6-2.7, P < 0.01) and those who were unable to make any future housing plans (OR = 1.9, 95%CI = 1.4-2.5, P < 0.01) exhibited a significantly higher risk of psychological distress compared with subjects who had already settled in permanent housing. CONCLUSION: In this study, subjects whose future housing prospects were under consideration and those who were unable to make any future housing plans were at a higher risk of psychological distress 1 year after the earthquake disaster.

Household evacuation characteristics in American Samoa during the 2009 Samoa Islands tsunami.

Tsunamis represent significant threats to human life and development in coastal communities. This quantitative study examines the influence of household characteristics on evacuation actions taken by 211 respondents in American Samoa who were at their homes during the 29 September 2009 Mw 8.1 Samoa Islands earthquake and tsunami disaster. Multiple logistic regression analysis of survey data was used to examine the association between evacuation and various household factors. Findings show that increases in distance to shoreline were associated with a slightly decreased likelihood of evacuation, whereas households reporting higher income had an increased probability of evacuation. The response in American Samoa was an effective one, with only 34 fatalities in a tsunami that reached shore in as little as 15 minutes. Consequently, future research should implement more qualitative study designs to identify event and cultural specific determinants of household evacuation behaviour to local tsunamis.

Regional differences in postneonatal childhood mortality in Finland, 1985-2004.

AIM: The Finnish healthcare system will undergo a major reform in the near future. This study examined whether postneonatal childhood mortality differed between university and central hospital districts in Finland from 1985 to 2004 and whether the causes of death were preventable. METHODS: We analysed postneonatal childhood mortality in Finland during two 10-year periods - 1985 to 1994 and 1995 to 2004 - analysing university and central hospital districts separately, as paediatric intensive care is centralised in university hospitals. The study looked at the main causes of death in each hospital, and the mortality rates were adjusted to demonstrate how many children were at risk of dying. RESULTS: Postneonatal childhood mortality decreased during the study period in university and central hospital districts. We found no significant difference in mortality rates between university hospital districts, but regional differences were notable in central hospital districts, partly because of historical differences in mortality. Accidents were the most common cause of death, with substantial regional differences. CONCLUSION: Regional postneonatal childhood mortality differed across central hospital districts, and this should be taken into account in the forthcoming restructuring of the Finnish healthcare system. Special attention is needed to prevent accidental deaths, both nationally and locally.

[Survey report on magnetic resonance equipment damage in areas in Miyagi Prefecture affected by the Great East Japan Earthquake].

A questionnaire comprising 14 items, inquiring about the state of damage, whether safety could be ensured, and progress of repair and restoration was distributed to 984 facilities in seven prefectures on the Pacific coast as part of a fact-finding survey of damage caused to magnetic resonance (MR) devices by the Great East Japan Earthquake. In all, 458 responses (46.6%) were collected. In Miyagi Prefecture alone, 65 responses from 105 questionnaires were collected (response rate: 61.9%). The overall incidence of damage was 19.2%, with 57 facilities (12.4%) reporting that displacement of the magnets was the most common problem. The damage event rate in Miyagi Prefecture was 51.3%, with displacement of the magnet being highest at 17 cases (26.2%). There was a high rate of 13 cases (26.5%) of chiller and air conditioning failures and a rapid loss of He in ten MR scanners (20.4%). Notably, 87.8% of facilities in Miyagi Prefecture (24.5% of the total) were affected by earthquakes exceeding 6 on the Japanese Seismic Intensity Scale. Flood damage caused by the tsunami was also seen along the Sanriku coast to Sendai City (six MR scanners, 50% of the total), and was typical of the damage seen in Miyagi Prefecture.

Increase in the number of patients with seizures following the Great East-Japan Earthquake.

In the afternoon of March 11, 2011, Kesennuma City was hit by the Great East-Japan Earthquake and a devastating tsunami. The purpose of this retrospective study is to document possible changes in the number of patients with distinct neurologic diseases seeking treatment following this disaster. Because of Kesennuma's unique geographical location, the city was isolated by the disaster, allowing for a study with relatively limited population selection bias. Patients admitted for neurologic emergencies from January 14 to May 5 in 2011 (n = 117) were compared with patients in the corresponding 16-week periods in 2008-2010 (n = 323). The number of patients with unprovoked seizures was significantly higher during the 8-week period after the earthquake (n = 13) than during the same periods in 2008 (n = 6), 2009 (n = 3), and 2010 (no patients) (p = 0.0062). In contrast, the number of patients treated for other neurologic diseases such as stroke, trauma, and tumors remained unchanged. To our knowledge, this is the first report of an increase in the number of patients with seizures following a life-threatening natural disaster. We suggest that stress associated with life-threatening situations may enhance seizure generation.

Impact of the 2004 tsunami on self-reported physical health in Thailand for the subsequent 2 years.

OBJECTIVES: We examined self-reported physical health during the first 2 years following the 2004 tsunami in Thailand. METHODS: We assessed physical health with the revised Short Form Health Survey. We evaluated 6 types of tsunami exposure: personal injury, personal loss of home, personal loss of business, loss of family member, family member's injury, and family's loss of business. We examined the relationship between tsunami exposure and physical health with multivariate linear regression. RESULTS: One year post-tsunami, we interviewed 1931 participants (97.2% response rate), and followed up with 1855 participants 2 years after the tsunami (96.1% follow-up rate). Participants with personal injury or loss of business reported poorer physical health than those unaffected (P < .001), and greater health impacts were found for women and older individuals. CONCLUSIONS: Exposure to the tsunami disaster adversely affected physical health, and its impact may last for longer than 1 year, which is the typical time when most public and private relief programs withdraw.