Professional Firefighters and PTSD: A Scientific Metrology Analysis Based on CiteSpace
Yiming Zang, Beijing National Day School, Beijing, China
High-frequency exposure of professional firefighters to traumatic events is a potential trigger for post-traumatic stress disorder (PTSD). A scientometric analysis of PTSD in firefighters was conducted to reveal the evolution, hotspots, and trends. The study found that inter-country cooperation is not strong, and most independent research is in developed countries such as the United States and the United Kingdom. The United States has made the largest contribution, whether in terms of the number of publications, impact, or collaboration with other countries. The global evolution of firefighter PTSD research is from PTSD symptoms and triggers to mental health care, with a focus on mental health and psychiatric rehabilitation. Frontier research will develop PTSD interventions that are more applicable to professional firefighters based on the occupational characteristics of "trauma exposure".
Keywords: Firefighters; PTSD; Co-occurrence analysis; CiteSpace
PTSD usually refers to a persistent or delayed psychiatric disorder after experiencing traumatic events (e.g., war, disaster, serious traffic accident). It contains four symptom clusters, namely intrusion, avoidance, negative alterations in mood changes, and arousal and reactivity changes (Bisson & Olff, 2021; Servick, 2021). Professional firefighters have a higher exposure to traumatic events, causing them to be more vulnerable. Researchers have calculated that firefighters suffer from PTSD three times more than the general population; the prevalence of PTSD among firefighters involved in the World Trade Center rescue was approximately 11%—19.5% (Heinrichs et al., 2005; Soo et al., 2012). Once a firefighter develops PTSD, it can last for months or years and may even be life-threatening. In recent years, there has been a gradual increase in attention to firefighter mental health in various countries, especially in developed countries.
CiteSpace software is an information visualization software developed by Professor Chaomei Chen and has been widely recognized in the global information science field (Li & Chen, 2016). However, there are no CiteSpace studies on firefighters’ PTSD. To summarize, this project analyzed research related to PTSD in firefighters to provide data and information to support subsequent research and to increase global attention to firefighterss' mental health.
In the Web of Science database, the terms "firefighter" and "PTSD" published between January 1, 2000, and May 1, 2022, were searched. Excluding non-English literature, conference papers, letters, etc., 277 relevant papers were obtained. The evolution of international collaborations and research hotspots over the last 20 years was analyzed using CiteSpace visualization software (6.1.R1 and 6.1.R2), with country, institution, and keyword as the node types. There was no pruning and the time slice was set to 1. The threshold value was Top50.
3. Visual analysis results
3.1 Country collaboration network
Figure 1 shows the visualization results of the inter-country collaboration regarding the firefighter PTSD study. The network of collaborating countries consists of 30 nodes and 35 links. This suggests that there are not many countries conducting research on firefighters’ PTSD and that international scientific cooperation on firefighter mental illnesses is not strong. The earliest collaborations were between the United States and Switzerland as well as between Germany and Switzerland, as differentiated by the link color. The United States is the largest contributor to firefighters’ PTSD research and has a substantial impact in this field of study, as evidenced by the 130 publications and 0.41 centrality value. With 25 publications, South Korea is a significant node in Asia. The nine articles contributed by China were all published after 2019.
Figure 1: A visualization of the country collaboration network.
3.2 Institution collaboration network
The results of the network analysis of research institutes and collaborations are shown in Figure 2. Two large collaborative teams and numerous smaller institutional partnerships are represented by a total of 263 nodes (representing institutions) and 403 connecting lines (showing collaborative links between institutions) in the co-occurrence mapping.
Washington University, Columbia University, and Harvard University are some of the early contributors to the field chronologically. There is increased cooperation between fire agencies and universities, particularly between Houston University, Florida State University, and Houston Fire Department. The cooperation between medical schools and universities, including Albert Einstein College of Medicine, New York University, and Boston University is also seen. Additionally, Nanjing Normal University in China collaborated with Beijing Normal University, Florida State University, and Northern Illinois University. The top 10 institutions are listed in Table 1 according to publication volume and centrality. In terms of centrality, Boston University and Mt. Sinai School of Medicine have had the greatest impact. In summary, the United States has been the largest contributor to PTSD research in firefighters over the past 20 years. The way of cooperation between its internal institutions is referential. Cooperation between transnational institutions will enhance cooperation among countries.
Figure 2: A visualization of the institution collaboration network.
Table 1: Top 10 institutions based on frequency and centrality.
3.3 Keyword visual analysis
3.3.1 Keyword co-occurrence analysis
Keywords are high-level summaries of this article's content. In CiteSpace, keyword co-occurrence analysis represents the frequency of keyword co-occurrence in a certain field (Li & Chen, 2016). A higher frequency and centrality indicate that a keyword has received more investigation in this field, i.e., it represents the research hotspot in this field.
400 network nodes and 2325 connection lines were formed as a result of the keyword co-occurrence analysis, as illustrated in Figure 3. The larger the node chronology, the higher the frequency of the keywords; the more node links, the stronger the centrality of the different keywords. When the centrality of the keywords is greater than or equal to 0.1, it indicates that researchers are very interested in the field covered by these keywords. The top 8 were ranked by keyword frequency and centrality (≥ 0.1) in descending order as shown in Table 2.
Figure 3: Keyword co-occurrence map of literature related to PTSD on firefighters.
Table 2: Keywords sorted by frequency and centrality.
3.3.2 Keyword clustering analysis
In keyword clustering graph analysis, the modularity (Q) is used to evaluate the validity of clusters, whereas the mean silhouette value (S) is used to assess the homogeneity of clusters (Tan & Yang, 2022). In general, it is believed that when Q>0.3, the clustering structure is significant; S>0.5 and S>0.7 indicate that the clustering is reasonable and convincing, respectively (Aryadoust et al., 2020). The smaller the clustering label, the more keywords are included in this cluster.
Figure 4 displays the keyword clustering view of the firefighters' PTSD research. The modularity value is 0.4576, the S value is 0.737, and Harmonic Mean (Q, S) is 0.5646, indicating that the keyword clustering structure is significant, and the clustering results are justifiable and credible. The largest clustering theme is #0—suicide, which concentrated on the firefighters' self-harm due to chronic illness, emotion regulation disorders, and mental sensitivity. The cluster with the highest S-value is cluster #7—first-responders, showing the highest level of homogeneity, with major keywords such as “vulnerability markers”, “risk markers”, “PTSD biomarker study”, etc., with an average citation time of 2014.
Figure 4: The keyword clustering view of firefighters' PTSD research.
3.4 Analysis of research trends
3.4.1 Time evolution analysis of keywords
The time zone view of keywords, also known as the topic path map, can arrange keywords according to the time of publication or peak time, thus showing the evolution process of research hotspots over time and the connection between keywords of each research hotspot (Li & Chen, 2016). Each node in the figure represents a hot keyword, and the larger the node, the higher the word frequency. The connecting line between keywords shows that the two keywords appear in the same article.
According to Figure 5, within the time frame studied in the literature on this topic, the peak of international attention to PTSD in firefighters was in 2002. Subsequently, studies on the symptom, exposure, and impact of PTSD were conducted. From 2004 to 2007, firefighters' depression, prediction and impact of event scale began to receive attention, and research hotspots included anxiety sensitivity, risk factors, psychometric property, psychiatric disorder, and health. In 2010, mental health and mental disorder became new research hotspots. It also represents a shift in the research on PTSD in firefighters from physical health to mental health. After then, meta-analyses, questionnaires and model analyses on firefighter mental health gradually increased (Meyer et al., 2012; Berger et al., 2012; Liu et al., 2014; Armstrong et al., 2014; Blevins et al., 2015).
Figure 5: Time zone view of keywords.
Between 2016 and 2019, the keywords about career firefighter, center exposed firefighter, and alcohol abuse became the research focus. Meanwhile, the impact of emotional disorders and social support of firefighters on PTSD has gradually become a hot research area (Miao et al., 2018; Huang et al., 2019; Stanley et al., 2019). It is worth noting that the attention paid to female firefighters increased during this period (Haddock et al., 2017; Jahnke et al., 2019; Watkins et al., 2019). In recent years, there have been a number of studies on "mental health care", "brief behavioral treatment", "insomnia crisis", "trauma exposure", "psychological distress", "job burnout", "emotional interference", and "cognitive function".
3.4.2 Analysis of keywords emergence map
The keyword emergence map was obtained based on the keyword co-occurrence network analysis, with the Minimum Duration set to 2 years, and the top 15 keywords with the strongest citation bursts were selected, as shown in Figure 6. It can be divided into three stages. The first stage was from 2002 to 2010, when the 9/11 attacks drew attention to major disasters. The emergent words during this period were "distress", "disaster", "response" and " predictor". Among them, "predictor" was the longest and strongest emergent word in this period. The second stage ran from approximately 2010 to 2016. "Recovery" and "impact" became the main emergent terms in the middle of the study. The third stage could be set from 2017 to 2022, such as "behavior" and "traumatic events" in 2017 and "resilience" and "risk" in 2019. The new emergence of "public safety personnel" in 2020 is the strongest emergent intensity in the last 22 years, with a value of 4.12.
Figure 6: Emergent distribution of keywords related to firefighter PTSD research.
Firefighters are public safety personnel whose occupation is to deal with emergencies. In addition to job stress, the sense of mission leads them to suffer from great mental stress such as stigma and emotional regulation difficulties. Frequent exposure to traumatic events causes them to be more prone than the general population to develop burnout such as anxiety and depression, and in severe cases, stress reactions and even PTSD. The prevalence of PTSD among firefighters in this study ranged from 1.6% to 57% (Sakuma et al., 2015; Alghamdi et al., 2016). Globally, firefighters of any country, race, cultural background, and age are at risk for PTSD. Although it has not become the focus of global public health in a short time like COVID-19, firefighters’ PTSD is indeed a global mental health issue. WHO and Collins et al. have suggested that PTSD needs to be addressed as a public health priority (Whiteford et al., 2015; Collins et al., 2011). From the perspective of public health, PTSD is considered as a chronic mental illness that requires timely treatment (Mat Salleh et al., 2020; Morina et al., 2014). Notably, PTSD as an occupational psychiatric disorder coexists with its occupation. It causes great psychological distress to individuals and a huge medical burden to families and countries.
With accelerated industrialization, increased social instability and natural disasters, the frequency and complexity of firefighter occupational activities have increased. Research has shown that firefighter behavioral health is positively correlated with emergency response capability, i.e., a healthy mental state improves response and operational capability (Shi et al., 2021). Conversely, poor behavioral health can reduce rescue efficiency, weaken public safety, and even put themselves and their teammates in danger. Although there are differences in firefighting systems and policies across countries, establishing global cooperation that is not limited to firefighter behavioral health can accelerate the maximization of benefits.
5. Future Directions
In the future, governments should raise risk defense awareness of firefighters' PTSD. While strengthening the cooperation between domestic fire departments and medical institutions, the cooperation in global mental health should be enhanced. On the other hand, developing countries and less developed countries should establish a sound firefighting training system to strengthen firefighters' operational level and improve their resilience under trauma. Furthermore, the incidence of mental illness can be reduced by adjusting the working pattern and environment of fire stations, such as increasing shifts, shortening duty hours, establishing decompression areas, and adding psychological instructors. Likewise, exploring interventions more suitable for firefighters' PTSD is a crucial job.
In summary, there are few countries studied regarding firefighters' PTSD, and few international collaborations. This echoes the differences in political structures, economics and policies in each country. However, to enhance common good of firefighters globally, countries need to seek common ground, maintain a sustained focus on firefighters' PTSD and share research findings. This is critical to maximizing the mental health benefits of all professional firefighters.
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