In 1997, the Czech Republic, Poland, and Germany were affected by the 1997 Central European flood, known as the Great Flood of 1997 (Figure 1). According to the Emergency Events Database EM-DAT, which is a global database on natural and technological disasters, the Great Flood of 1997 was one of the top 10 natural disasters in the Czech Republic for the 1900 to 2013 period with regard to the number of people killed (29), the total number of people affected (102 107), and the amount of economic damage (US$1 850 000 000).Reference Guha-Sapir, Below and Hoyois 1 The flood was caused by heavy precipitation that fell from 4 to 8 July 1997. During this period, more than half of the entire year’s typical rainfall fell in the catchment area of the Oder and the Morava rivers. Both of these rivers and their tributaries had overflowed to a level approximating a 150- to 500-year flow rate. The flood itself appeared during the first half of July in 1997 (5 to 16 July 1997). The highest flood stage ended on 29 July 1997. The flood affected 538 residential zones in 34 counties in Moravia, Silesia, and the eastern part of the Czech Republic. It destroyed 2151 houses, and another 5625 houses would not be habitable without extensive reconstruction. Many cities remained without electricity or phone service and hundreds of people had to leave their homes. 2
Map of Areas Affected by the 1997 Central European Flood. Source: http://povodne.charita.cz/1997/kniha-povodne-1997/
Studies show that acute mental stress may trigger a cardiovascular event.Reference Schwartz, French and Mayeda 3 , Reference Hemingway, Malik and Marmot 4 Increased rates of cardiovascular events are typically found after various life stressors, such as early wake-up times,Reference Muller, Ludmer and Willich 5 , Reference Muller 6 work-related stressful events,Reference Moller, Theorell and de Faire 7 , Reference Kales, Soteriades and Christophi 8 bereavement,Reference Kaprio, Koskenvuo and Rita 9 , Reference Parkes 10 and community-wide events such as wars,Reference Kark, Goldman and Epstein 11 , Reference Meisel, Kutz and Dayan 12 terrorist attacks,Reference Goldberg, Spencer and Lessard 13 - Reference Steinberg, Arshad and Kowalski 15 and industrialReference Ruidavets, Paterniti and Bongard 16 and natural disasters. An excess of deaths from cardiac causes was reported after the Athens earthquake in 1989;Reference Trichopoulos, Katsouyanni and Zavitsanos 17 on the day of the Northridge earthquake in Los Angeles, California, in 1994;Reference Leor, Poole and Kloner 18 and also after the 1995 Great Hanshin-Awaji earthquake in Japan.Reference Ogawa, Tsuji and Shiono 19 Significant increases in the occurrence of heart failure and in the in-hospital mortality rate of heart failure were also described after the earthquake and tsunami disaster.Reference Nozaki, Nakamura and Abe 20 - Reference Nakamura, Satake and Abe 22
Floods are the most common and most destructive natural disaster worldwide. Despite this fact, we could not find any similar studies concerning the effect of floods on the cardiovascular system. In industrialized countries, several articles refer to increases in total mortality following flood events.Reference Bennet 23 However, a study of the 1974 Brisbane floods did not support this.Reference Abrahams, Price and Whitlock 24 We were therefore interested in whether flood disaster increases the incidence of death from ischemic heart disease and heart failure by use of actual autopsy results. It is known that approximately 50% of all cardiac deaths are sudden, occurring within 1 hour of the onset of symptoms in a person with known or unknown cardiac disease. Most cases of sudden cardiac death have coronary artery disease present at autopsy, although in approximately 50% of cases this disease will not have been clinically apparent prior to death.Reference Hemingway, Malik and Marmot 4
Methods
This was a retrospective case-control study. Data were obtained from the archive of the Institute of Forensic Medicine, Palacky University Olomouc, with permission from the Institute. The Institute of Forensic Medicine investigates sudden, unexpected death, deaths for which it is not possible to unambiguously determine the cause of death and deaths not from natural causes. Each autopsy is conducted by specialists in forensic medicine. These specialists write autopsy reports that are archived. In 1994 to 1997, only paper archiving existed. All autopsy reports had to be reviewed manually. Data collection took place in 2012 to 2013.
The authors (trained medical professionals) personally reviewed all autopsy reports from July 1997, the month of flood; from 1 month after the flood (August 1997); and from 2 months before the flood (May and June 1997). Because no studies concerning the impact that floods have on death from cardiac causes were found, an 8-week follow-up from the beginning of the flood was derived from a study examining the impact of another natural disaster, the 1995 Great Hanshin-Awaji earthquake. The duration of increased cardiac mortality after this earthquake was longer than had been observed with previous earthquakes.Reference Ogawa, Tsuji and Shiono 19
Persons who died of ischemic heart disease (I20-25 of The International Statistical Classification of Diseases and Related Health Problems, 10th Revision, WHO ICD-10) and heart failure (I50 of WHO ICD-10) as a cause of death according to performed autopsies were included in the study.
The authors obtained similar data for the corresponding period in the previous 3 years (1994, 1995, 1996). Data were manually entered into the database for analysis.
SPSS software version 15 (SPSS Inc, Chicago, IL) was used for the statistical analysis. The incidence of cardiac death in individual years and other categorical data were compared by using the chi-square test and Fisher's exact test. The Kruskal-Wallis test was used to compare age and the normality of the data was verified by using the Shapiro-Wilk test. Tests were conducted with a significance level of 0.05.
Results
A total of 985 deaths were investigated in the Institute of Forensic Medicine, Palacky University Olomouc, from May to August 1994 to 1997 (Table 1). The inclusion criteria were matched in 207 cases that were included in our study. No significant differences in cardiac mortality from 1994 to 1997 were found (p=0.544). The average age of persons in 1997 was identical to that in 1994–1996 (p=0.577). Also, gender was similar compared to the control period (p=0.819). The basic data are summarized in Table 2.
Total number of deaths for the year, total number of deaths during the monitored period (May-August), and total number of deaths from cardiac causes during the monitored period (May-August)
Total Number, Average Age, and Sex of Persons Who Died of Cardiac Causes, May–August 1994 to 1997
No significant difference in the distribution of cardiac mortality in individual months was found (p=0.088; Table 3). During the flood in July 1997, 25 persons were found who died from cardiac causes: 18 men and 7 women with an average age of 64.5 years. This was the most cardiac deaths in all the monitored months. Compared with the same months in previous years, there was a noticeable increase (10 in 1994, 7 in 1995, 19 in 1996); however, this increase did not reach statistical significance. The month of the flood month saw more than twice the number of cardiac deaths than the 2 months preceding the flood (10 in May, 9 in June). However, this difference still did not reach the threshold of statistical significance. In the month after the flood, we noticed a decrease in cardiac mortality compared with previous years.
Number of Deaths From Cardiac Causes in Individual Months, May to August 1994 to 1997
The daily number of deaths from cardiac causes in July 1997 is shown in Figure 2. The exact date of one death was not possible to determine and the most probable date was assessed at 18.7.±6 days. During the most critical days (5 to 16 July 1997), nearly one-third of the persons died (28%, 7 persons). However, the greatest number of deaths were recorded in the following week (52%, 13 persons).
Daily Number of Deaths From Cardiac Causes in July 1997.
Death from ischemic heart disease or the combination of ischemic heart disease and heart failure dominated in all monitored months (Table 4). Heart failure itself was found at a very small percentage. There was no significant difference in the cause of death in individual months.
Number of Deaths According to Cause of Death, May–August 1994 to 1997
Discussion
Little is known about the effect that floods have on death from cardiac causes. This study investigated the influence of one of the largest floods in the history of the Czech Republic. Acute mental stressors are now considered acute risk factors for cardiovascular events.Reference Schwartz, French and Mayeda 3 In our study, an increase in autopsy-proved deaths from cardiac causes in the month of the flood compared to the 2 previous months was observed. The same trend was also seen when compared with the previous 3 years. However, this increase did not reach statistical significance. The uniqueness of this study is that it included only autopsy-proved deaths from cardiac causes. But this is also a limitation of the study, because not all deaths are autopsied. Because we expected an increase in sudden cardiac deaths, we decided to obtain data from the archive of the Institute of Forensic Medicine, Palacky University Olomouc, which investigates sudden and unexpected death. However, no statistically significant increase was noticed.
The greatest number of deaths were recorded not during the most critical days of the flood, but in the following week. During that time, the flood began to retreat and people started to return to the affected areas. This finding may suggest that facing the aftermath of the flood was a greater stress for the victims than the flood itself.
Research identifying flood-related morbidity and mortality risk factors has revealed that during floods, females, the elderly, and children appear to be at greater risk of psychological and physical health effects, whereas males aged 10 to 29 years may be at greater risk of mortality. Post-flood, those over 65 years of age and males are at an increased risk of physical health effects, whereas females appear at greater risk of psychological health effects.Reference Lowe, Ebi and Forsberg 25 In our study, the elderly and males predominated, which is in line with the most common cause of death, ischemic heart disease. However the age and sex of persons who died of cardiac causes during the flood and control period were similar. This finding may suggest that the monitored increase in deaths occurred among people already at risk of death and that these persons merely died earlier because of the flood. To support this theory, we would expect a decrease in cardiac mortality in the next period. The month after the flood, cardiac mortality did decrease.
While ischemic heart disease increased during the flood, heart failure was autopsy-proved in only a very small percentage and did not show any changes during the time of the flood. The reason for this finding may be again be due to the study’s design, which analyzed only autopsied persons from the Institute of Forensic Medicine, Palacky University Olomouc.
Another limitation was that the study was retrospective. The study design did not allow us to obtain information about how the individuals actually experienced the disaster and whether they suffered any material or immaterial damage. It is questionable whether a detailed geographic analysis would provide a different result. The entire catchment area of the Institute of Forensic Medicine in Olomouc was affected by the flood. Analysis would show whether the deceased lived near a swollen river or a tributary, so one could assume greater property damage. However, damage to a particular house or apartment could not be traced.
Conclusions
Floods are the most common and most destructive natural disaster. Studies concerning their effect on human health are needed in order to prepare preventative strategies. We analyzed the influence of one of the greatest floods in the Czech Republic on cardiac mortality in the affected area by using autopsy results. Despite the observed increase in deaths from ischemic heart disease, the 1997 Central European flood did not significantly affect cardiac mortality.
Acknowledgments
This study was created within the Operational Program Education for Competitiveness, the Implementation of Modern Methods from eHealth to Teaching Medicine project, ID: CZ.1.07/2.2.00/28.0146, and was co-financed by the European Social Fund and the state budget of the Czech Republic.
