In South Korea, firefighters are civil servants, whose duties involve emergency rescue, fire prevention, monitoring fire risk, and extinguishing fires. The functional aspects of firefighting duties can be classified into fire safety and volunteer functions. Moreover, firefighting duties have special characteristics in terms of risks, 24-hour shifts, and working environments, compared with the duties of other civil servants.¹ In addition, firefighters require robust physical fitness to manage the health-related risks, emergencies, and unusual environments in which they work. Although there may be differences in the types and characteristics of activities, fire-fighting involves life-threatening risks, such as exposure to toxic gases (including carbon monoxide and phosgene), death or injury, and accidents caused by unforeseen explosions. Moreover, firefighters are required to act immediately, whether firefighting or conducting rescue and first aid activities, in order to reduce risks to survivors. As such, firefighters are exposed to a range of serious risks in the course of their duties, and the likelihood of emotional stress and other work-related diseases is high.²

Nevertheless, there are very few studies of firefighters' exposure to risk or biological monitoring of firefighters; studies of the effect of firefighters' duties on their health are limited to an examination of occupational stress, posttraumatic stress disorder (PTSD), and physical diseases, including pulmonary dysfunction, respiratory symptoms, noise-induced deafness, musculoskeletal diseases, and cancer.³⁴⁵⁶ However, a recent study reported a high prevalence of functional gastrointestinal disorders (FGIDs) in firefighters.⁷ In particular, irritable bowel syndrome (IBS), caused by the irregular working environment and work structure involving high stress, appears to impose a serious burden on firefighters' health.

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder characterized by chronic, relapsing abdominal pain or discomfort and disordered defecation.⁸ The prevalence of IBS in the general population is estimated to range from 3% to 20% based on the Rome III criteria.^9101112 Although the symptoms of IBS often impair the patient's quality of life (QOL), many individuals with IBS ignore their symptoms and tend not to seek medical care.¹³

Psychological factors such as stress play an important role in the onset of IBS.¹⁴¹⁵ Several community studies comparing the psychological profiles of consulters, non-consulters, and controls free of symptoms from the same population have demonstrated that consulters with IBS had significantly higher anxiety and depression scores than either the non-consulters or the controls.¹⁶¹⁷ The quality of life (QOL) of patients with irritable bowel syndrome (IBS) is closely related to disability, health care resource utilization, and clinical response to treatment.¹⁸¹⁹ Therefore, it is crucial to understand the factors that affect the quality of life of IBS patients; these factors include extra-intestinal symptoms, psychiatric symptoms, disease severity, and sex.²⁰ The health-relatedquality of life of IBS patients is similar to that of patients with diabetes mellitus, cancer, and end stage renal disease, and is lower than that of general population.²¹²²

Although the prevalence of IBS is high in firefighters and psychological factors are strongly associated with IBS manifestation and its aggravation, there are very few studies of the relationship between IBS and particular psychological factors. Therefore, this study investigated the characteristics of the psychological factors that are related to IBS and their effects on the quality of life of firefighters in South Korea.

Various psychosocial factors put firefighters at a high risk of experiencing psychological and physical diseases. Psychosocial factors are very closely related to FGIDs, including IBS.³⁵ Although some studies have reported the prevalence of overlap syndrome in FGIDs, research into the role of psychological factors in affecting quality of life is very rare.³⁶ Therefore, we aimed in this study to identify differences in demographic and psychosocial factors in firefighters with IBS and those without IBS, and to assess the effects of these factors on quality of life.

The incidence of IBS in this study was 9.1% (111 individuals). The prevalence of IBS reported in previous studies of the general population ranged between 4.4% and 19.4%. Despite the target population having a higher level of work-related stress in this study, the prevalence for IBS was relatively low. Previous studies have reported a substantially higher prevalence of IBS in females than in males. The relatively low prevalence of IBS in this study may be the consequence of the pre-ponderance (94%) of male participants.^37383940 The subtype “IBS-mixed type” was the most common type (47.7%) of IBS among the participants, and this finding is in line with that of previous studies.⁴¹⁴²⁴³

Significant differences were observed between the IBS-positive and IBS-negative groups for the psychosocial factors of depression, anxiety, occupational stress, self-esteem, and quality of life. In a previous study by Fond et al.,⁴⁴ patients with IBS had significantly higher anxiety and depression levels than controls. Lee et al.⁴⁵ reported in their community-based study that depression and chronic stress can cause IBS. In addition, Stanculete et al.⁴⁶ identified the role of irrational cognition and coping mechanisms in patients with IBS. The relationship between psychosocial factors and IBS has been explained by two major theories. First, the concept of a dysregulated gut-brain axis has been adopted as a suitable model for IBS.⁴⁷ Second, the gut microbiome may play an important role in the onset and exacerbation of symptoms of the disorder.⁴⁸

The findings of this study agree with previous studies in terms of context; moreover, by investigating differences in occupational stress, self-esteem, and stress coping styles that have not been investigated previously, the present study has broadened the scope of understanding of psychosocial factors in IBS.

The high-risk group in the subdomains of occupational stress including job demand, interpersonal conflict, organizational system, and lack of reward had a higher probability of IBS. Previous studies also reported that IBS has a very close association with stress. In a study by Koh et al.,⁴⁹ the prevalence of psychosocial stress among nurses who work rotating shifts is associated with the development of functional gastrointestinal disorders. Eriksen et al.⁵⁰ reported that occupational stressors such as patient care, team conflicts, role ambiguity, and lack of autonomy were some of the contributing factors to IBS. Qin et al.⁵¹ reported that psychological stressors have a marked impact on intestinal sensitivity, motility, secretion, and permeability. In this study, stress due to interpersonal conflict and occupational climate, in addition to occupational characteristics, exerted a substantial influence on IBS, possibly influenced by the hierarchical organization and a public service system focused on command and discipline. These create Korean occupational environments that are very different from Western occupational environments.

PHQ-9, KOSS, and RSES, which account for 42.6% of the variance in the total QOL, are factors that influence the quality of life of the IBS group. When Park et al.⁵² evaluated health-related quality of life using SF-36 questionnaires, IBS patients had lower QOL scores in all areas, in comparison to the control group. Moreover, Amouretti et al.'s study,⁵³ suggested that continuous pressure was a factor that reduces the quality of life in IBS patients. Although quality of life differs depending on the presence or absence of IBS in previous studies, the studies did not report which psychosocial factor was important in this aspect; therefore, the findings of the present study are significant.

The limitations of our study include that fact that, first, it was a cross-sectional study, so we could not assess effects over time. Second, we used self-reported data to evaluate psychological variables; therefore, there was the possibility of researchers' subjective bias, and there was no study of the severity of IBS symptoms. Third, since it was a population-based study, our study did not include endoscopy data. Finally, because we investigated firefighters, a specific occupational group, it is difficult to generalize the results to the characteristics of all IBS patients. Fifth, since the proportion of male subjects was extremely high (94%), we could not confirm differences by sex.

Nonetheless, this study was conducted with a large number of participants with IBS; the study also is advantageous in examining the influences of occupational stress, stress coping styles, and self-esteem, which have not been investigated previously. In addition, the study is significant, as it has suggested a new approach to the physical and psychological health of firefighters, which recently has become a social issue.

Future research into the influence of various psychosocial factors on IBS would expand present knowledge about the illness. Simultaneous physical and mental health approaches should be undertaken in the treatment of IBS. Moreover, more interest and research into the mental health of those employed in disaster control jobs, including firefighters, is necessary.