The threaten of typhoons to the health of residents in inland areas: a study on the vulnerability of residents to death risk during typhoon “Lekima”

Global warming aggravates the instability of the climate system, leading to the increasing frequency of extreme weather events [1, 2]. Typhoon disasters, as extreme weather phenomenon, have occurred in many countries in recent years. China is one of the most vulnerable countries to typhoon disasters currently [3‐5]. There are seven typhoons or tropical cyclones that make landfall from coastal provinces of China each year, and the spatial patterns of the disasters for typhoons with different landing paths were significantly different [6, 7].

Typhoon is familiar with its impact on the coastline, such as storm surge, strong wind. Most typhoons weaken rapidly once they encounter land [8]. With the depletion of storm “fuel” –– the heat and water extracted from the ocean, the force of typhoon gradually weakens. However, with global climate change, the typhoon hazards have become unpredictable. Jeffrey confirmed that the lethal range of the typhoon was not limited to the coastline [9]. The “inland stage” of typhoon ––namely, the second storm, may cause more deaths and property losses in inland areas than those in coastal areas. The inland areas are located far from the coastline and major rivers [10]. At the initial stage of the typhoon's migration to inland areas, its power has weakened, but it may rejuvenate or re-strengthen after the transition of temperate climate. After the transition, the typhoon becomes a dangerous mixed cyclone. The impact of “second typhoon” on inland areas is diverse, and the common denominator is destruction [8]. The chain disasters caused by typhoons, such as rainstorm and flood, have produced hundreds of fatalities. This thus, the vulnerability of inland areas due to the second typhoons should be paid more attention to.

Typhoon Lekima, the most powerful typhoon in 2019, made landfall in Wenling City, Zhejiang Province, China on August 10. The maximum wind speed reached level 16. Typhoon Lekima affected 14,024,000 Chinese residents, caused 57 deaths, 14 missing, and 2,097,000 residents to require emergency care. The direct economic loss was more than 8.43 billion US dollars, and the indirect economic loss was unquantifiable, especially the health risk caused by typhoon disaster was enormous, which was difficult to estimate [2, 5, 11]. In August 11, the typhoon Lekima landed in Jinan, and had a devastating impact on Jinan in just three days. As the capital of Shandong Province, Jinan has become the core connection center of the Yangtze River Delta and Beijing-Tianjin-Hebei economic zones, with a population of nearly 7.6 million in 2019. It is a typical inland city in China [12]. Previous studies showed that compared with other inland cities, the vulnerability index of Jinan exposed to typhoon is over 0.2, which belongs to a highly vulnerable city [13, 14]. Therefore, it is representative to explore the typhoon Lekima and Jinan.

Many previous studies have illustrated that increased risk of death of residents was associated with typhoons. Existing studies mainly focused on the total death distribution or the incidence of infectious diseases of residents in the coastal areas [15]. The reported results only covered a short period, which paid more attention to the direct fatalities during the typhoon days [16, 17]. It is little known about the impact of typhoons on the health of inland residents, especially in China. However, many findings had shown that from 1970 to 1999, typhoon-related deaths mainly occurred in inland areas, especially in areas that had never experienced typhoons [13, 18, 19]. There were more vulnerable in residents who lack experience in resisting typhoon disasters (adaptive behavior) [15]. Additionally, the health impact caused by the “inland stage” of typhoons is not limited to the direct effect, and the threat brought by the lag effect cannot be ignored. McKinney found that the direct death caused by typhoons accounted for only 4%, and the indirect death caused by typhoon-related cardiovascular diseases, malignant tumors, diabetes and accidents accounted for 67% [20]. Therefore, it is vital to explore indirect death risk (lag effect) caused by typhoons in inland areas.

This study aims to identify the vulnerability of residents in Jinan on typhoon Lekima. Specifically, we will first investigate the acute effect of typhoon Lekima on mortality of residents in Jinan. Second, we will explore the difference of acute death risk among different subgroups during typhoon Lekima. This study will provide scientific evidence about emergency response in extreme weather in inland.

This study focused on the health vulnerability of vulnerable groups affected by climate change. We conducted a comprehensive exploration of the concept of health vulnerability. In the research about health vulnerability, we regarded typhoon as a disaster-causing factors, and comprehensively analyzed the acute death risk of residents during Lekima for the purpose of reducing population health vulnerability. Our research not only enriched the findings of environmental health, but also could provide a new theoretical perspective.

Our findings showed that the acute death risk of residents living in Jinan increased significantly in two weeks after the typhoon Lekima. The vulnerability of residents with different disease types, gender, age, and regions was different. The risk of direct death among residents in Jinan did not increase during Lekima, which was consistent with a previous study in Guangzhou [32]. The possible reason was that typhoon warning system has been continuously improved. The advanced warning system would help the public capture the forecast and real-time information of typhoon easily, which played an important role in emergency evacuation. Additionally, previous studies showed that the shocking adaptability among residents to typhoons might reduce of direct mortality [9].

Our study found that the increased risk of death from non-accidental diseases was significant from the Lag8 after the typhoon, with cardiovascular disease occurring earliest and lasting the longest. There was no evidence that the typhoon was associated with an increased risk of accidental death. Compared with accidental death (such as drowning death), it was difficult to capture the increased risk of circulatory with traditional disaster monitoring methods [27]. These non-accidental deaths were not directly caused by the physical forces of typhoons, nor were they rare during non-typhoons [14, 27]. During the landing of Lekima, the rainstorm caused by the typhoon flooded many roads, destroyed lots of trees and buildings, and interrupted public transport in Jinan. The possible reason for the increased risk of cardiovascular disease death was related to the disruption in treatment of chronic conditions caused by blocked transportation and damaged communication infrastructure [33]. It will take some time to clean up the damaged roads and restore communications, which might cause residents with circulatory diseases to miss the prime treatment time. Traumatic psychological consequences and a high prevalence of anxiety-mood disorders were evident after Typhoon, that might also a significant reason for the increase in heart attacks and cardiac arrest [16, 34]. Thus, the typhoon could be likened to an emotional button, which would exacerbate the risk of acute myocardial infarction [27]. In addition, the typhoon made landfall during the high temperature period, the combined effect of high temperature and humidity might lead to an increase in blood viscosity and cardiac output which may result in dehydration, hypotension, surface blood circulation increases and even the impairment of peripheral vascular endothelial function, then contribute to mortality events [35‐37]. We also had found a slight correlation between the risk of respiratory death and this typhoon. The increased risk of death from respiratory diseases was significant from the Lag12 after the typhoon and lasted for two days. A few previous epidemiological studies enlightened us that the high morbidity of chronic obstructive pulmonary disease during typhoons would increase the death risk of respiratory diseases [38, 39]. The deaths of respiratory disease might be related to disrupted power supplies for breathing aids. Meanwhile, the high winds could spread the particulates into the air, exacerbating chronic respiratory diseases [40].

Interestingly, we found that the significant increase in risk of death among female occurred on Lag7 after the storm and lasted for three days. This phenomenon was not found in the male group, which was contrary to the results of a Guangzhou study [32]. Compared with Guangzhou, the traditional Chinese family value of female residents living in Shandong were deeply ingrained. However, family value emphasized traditional sense of responsibility and belongingness. Female residents had suffered most of the housework burden at home and dedicated a lot to their family. The chain disasters caused by typhoon greatly increased their physical and psychological burden. Second, women, as a relatively vulnerable group, were more difficult to obtain the economic opportunities and productive resource opportunities to deal with climate change [41]. Then, a few previous epidemiological studies enlightened us that female residents suffered from greater psychological pressure than men after natural disasters, and were more likely to show their vulnerability to psychological and physical health [42, 43].

Consistently, the older adults (≥ 65) were more vulnerable than the young group during the typhoon. Bell found the sizeable increase in older inpatients during eight separate hurricanes of American [44]. Weinberder referred that the increase in the proportion of emergency department visits due to cardiovascular disease, respiratory disease and kidney disease among the older adults (≥ 65) was associated with Hurricane Sandy [14]. These results added further evidence to prove that typhoons would increase the risk of death and illness of the older adults through multiple pathways. Several possible explanations for this finding are as follows. First, with the gradual aging and the decline of physical function among older adults (such as mobility inconvenience), the adaptability to the changes of the external environment might be worsen. Especially, when expose to high temperatures, elderly persons’ ability to regulate their body temperature is weaker than that of the young [45, 46]. Second, the high prevalence of chronic diseases in older adults would increase their psychosocial stress. The risk of death in older adults increased due to the lack of routine medical care and drugs when the typhoon landed [27, 33, 47, 48]. Additionally, we also explored finer strata of age which showed that the typhoon had an impact on the increased risk of death among 65–74 age group.

Our study showed that the acute death risk of Jinan residents living in different areas appeared at different point-in-time during typhoon Lekima. The acute death risk of residents in TQ and CQ appeared earlier, and those living in other areas (except ZQ and PY) appeared from Lag8 to Lag13 after the typhoon. LC and ZQ as the typhoon landing areas, we found that the risk of acute death in LC increased during the typhoon, while ZQ did not. The reason for the phenomenon might be related to the timely and sufficient emergency rescue operations during this typhoon. ZQ was located in the plain, which allowed rescuers to carry out emergency rescue operations in time and evacuate affected residents. Meanwhile, the government agencies prepared the emergency shelters, which equipped with clean drinking water, sufficient daily supplies and comprehensive medical services [49]. The comfortable environment might reduce the spread of infectious diseases after disasters, pacify the panic of victims, improve the quality of life, then reduce the lag effect on health caused by the typhoon [50]. Although LC also carried out rescue operations timely, the geological features of vertical and horizontal gullies in Nanshan of LC made the rescue mission difficult [51]. In addition, the severe destruction to local infrastructures caused by this typhoon might also increase the risk of direct or indirect death among residents. Therefore, when formulating the emergency planning for typhoon, it was necessary to pay more attention to the mountainous terrain along the track of typhoon [6].

In conclusion, we provide some specific recommendations. Firstly, the government agencies should improve their emergency and disaster management response mechanisms to reduce the threat to life caused by subsequent typhoons. Secondly, the community agencies should improve the ability of dealing with emergency, such as conducting knowledge seminars on disasters, carrying out evacuation drills, while guiding residents to cultivate their crisis awareness. Meanwhile, when receiving a typhoon warning signal, community agencies should inform residents with chronic diseases to prepare sufficient treatment drugs and equipment in advance. Thirdly, rescuers need to carry out emergency rescue operations in time and evacuate affected residents during the typhoon landing period. As for areas where are hard to carry out rescue missions, the government agencies should organize residents to evacuate in advance and prepare temporary accommodation for them. Then, the temporary accommodation should equip with clean drinking water, sufficient daily supplies and comprehensive medical services. Finally, the psychological issues of victims cannot be ignored. Professionals should conduct psychological counseling of anxiety and depression regularly, especially for women and the older adults.

Our study had several strengths. To our knowledge, it was the first Chinese study to discuss the vulnerability of inland area during typhoons. Second, the accurate and reliable datum ensured the credibility of this research. Third, compared with the traditional design, we used the time-stratified case-crossover design to control the temporal trend automatically. Then, we compared the death in the unexposed period from 2016 to 2018 with the five-day moving average death of residents in August 2019, which made our results more credible.

This study demonstrated an acute death risk of residents during inland Typhoon with individual and regional scale characteristics as subgroup to identify the vulnerability during typhoons. The typhoon Lekima had increased the vulnerability of Jinan residents, and the mortality risk of different vulnerable groups appeared at different point-in-time. From the seventh day after Typhoon Lekima, the risk of death among residents with circulatory system diseases, women, the older adults increased significantly. The significant risk of death for most vulnerable groups appeared on Lag8, reached the maximum on Lag9 and Lag10. And the risk among residents living in TQ and CQ increased significantly on Lag2 and Lag6, respectively. In contrast, those living in LX, LC, HY, JY, and SH increased significantly from Lag 8 to Lag 13 after the typhoon. The greater vulnerability of residents living in the mountainous area (Nanshan) had made the longest duration of mortality risk in LC. Future efforts should focus on accurate identification of vulnerable groups and developing emergency plans for natural disasters. We should adjust measures to local conditions in natural hazards loss, also the contingency plan should be implemented step by step according to current conditions.