Nowadays, with fierce job competition, tense interpersonal relationships, higher technical requirements and levels of work intensity, the incidence of job burnout has aroused widespread concern in the scientific community (1). Research on burnout began with Freudenberger (2) and Maslach (3), among others. It refers to emotional exhaustion, personality disintegration, and a decreased sense of accomplishment, and can occur in the service industry or medical field in response to excessive working hours, too much work, and working too intensely, ultimately bringing about a series of physiological and psychological changes in the individual (4). Burnout has been found to be a significant predictor of hypercholesterolemia, type II diabetes, coronary heart disease, cardiovascular disease, sexual dysfunction, musculoskeletal disorders, headaches, and gastrointestinal problems, and people with burnout also exhibit a chronic decline that includes profound fatigue, insomnia, dizziness, nausea, allergies, dyspnea, menstrual irregularities, swollen glands, sore throats, recurrent colds, and in some cases, more severe gastrointestinal problems, ulcers, and hypertension (5–12). Job burnout can affect employees' turnover intention through the intermediary role of organizational commitment or job satisfaction. Higher levels of job burnout show a stronger relationship with turnover intention. Moreover, job burnout may also lead to a decline in the quality of employees' work (13–16).

The factors influencing the occurrence of burnout are generally determined by two factors: environmental factors and genetic factors. The environmental influences are work-related factors (17–19), individual characteristics (20–22), and moderating factors (23–25). It has been suggested that burnout may be closely related to the Hypothalamic-Pituitary-Adrenal axis (HPA) (26). The regulation of the HPA axis mainly depends on glucocorticoid receptor (GR) and mineralocorticoid receptor (MR). Li's (27) previous study showed a close relationship between glucocorticoid receptor and job burnout; for example, the rs41423247 locus of the GR gene is a susceptible genotype for burnout compared to the CC genotype (OR = 4.00, 95%CI: 1.845–8.671); the rs17209237 locus of the GR gene is a susceptible genotype for burnout compared to the GG genotype (OR = 2.674, 95%CI: 1.346–5.312); and the AA genotype has been identified as a susceptible genotype for burnout (OR = 2.674, 95%CI: 1.346–5.312). The CT genotype is a susceptible genotype for burnout compared to the CC genotype in the rs258747 locus of the GR gene (OR = 1.923, 95%CI: 1.1.252–2.954) (28). The gene product of nuclear receptor subfamily 3 group C member 2 (NR3C2), salt corticosteroid receptors, is distributed in brain regions mainly in the hippocampus and amygdala, while NR3C2 has a role in determining the activation threshold of the hypothalamic-pituitary-adrenergic axis (HPA axis). The NR3C2 is an important gene involved in stress response and is closely related to the anxiety generation and regulation (29, 30). Van Leeuwen et al. (31) investigated the relationship between the rs5522 locus and the stress response, and found that its haplotype may contribute to individual differences in chronic stress perception as well as neuroendocrine and cardiovascular stress responses. The study reported high polymorphic information at the rs2070950 and rs5522 loci, and therefore, served as the genetic polymorphic loci for this study.

China is currently the world's largest producer and consumer of coal (32), with coal resources accounting for 95% of the total domestic fossil energy resources. Coal mine workers work in a special environment, and are subjected to difficult working conditions and psychological pressure. Years spent working in this type of poor environment can easily contribute to the onset of pneumoconiosis, chronic obstructive pulmonary disease, musculoskeletal disorders and other diseases among coal workers (33, 34). In addition, the underground environment of coal mines is very complicated. Water, fire, gas, and coal dust always threaten the lives and safety of coal miners, and cause great psychological pressure. Long-term shift work in coal mines has a sizeable negative impact on the body and mind (35).

The relationship between genes and diseases has become a hot topic in the field of life science. This study explored the relationship between occupational stress, coping styles, NR3C2 gene polymorphism interaction and job burnout in coal miners, and provided scientific basis for revealing individual differences in job burnout. This study provides a new strategy to screen the population susceptible to job burnout, and provides a scientific basis for coal mining enterprises and the government to propose a reasonable employment system, improve the working conditions of coal miners, and prevent and treat job burnout. Moreover, this study provides a scientific basis for the career choice of individuals who want to work in coal mining related fields.

The survey results showed that among the 1,282 respondents, 128 (10.0%) had zero burnout, 400 had mild burnout (31.2%), 649 had moderate burnout (50.6%), and 105 had severe burnout (8.2%). The detection rate of worker burnout was 90.0%. Male coal miners had higher burnout scores than females, consistent with the findings of Gao et al. (44). Compared to female coal miners who work on the surface, male coal miners had a higher risk factor and higher levels psychological stress than females working in the underground working environment. The burnout scores of coal miners in the >45-year-old group were higher than those in the ≤ 35-year-old group and the 35–45-year-old group, consistent with the survey results of Sun et al. (45) on copper-nickel mine workers. The burnout scores of coal miners with a college education, technical secondary school education and above were lower than those of the other two groups, consistent with the survey results of bus drivers reported by Wang et al. (46). With regards to medical staff, divorced, and widowed coal miners had higher burnout scores than unmarried and married workers, which was in line with the findings of Zhang et al. (47). There was no significant difference in burnout scores between married and unmarried groups, consistent with Du and Zhu (48), which may be because divorced and widowed employees have higher stress levels than the other two groups (49), and subjective stress, psychological stress, and physical stress may all increase the level of job burnout (50). Coal miners with economic income >100,000 yuan/year scored lower than the other two groups on the dimension measuring a reduced sense of achievement, which was in agreement with the research results of Liu et al. (51). Workers with a low working ability and high income may have a more positive attitude toward their own working ability. Coal miners with more than 10 years of work experience had higher scores on the dimension corresponding to emotional exhaustion, personality disintegration and occupational burnout than those with less than 10 years of work experience, which was consistent with the research results of Yang et al. (52). The high physical intensity of repetitive labor tends to cause workers to feel disinterested and mentally exhausted. Coal miners in the excavation group scored higher on the personality disintegration dimension and had higher levels of job burnout than the other groups. Participants who worked fixed day shifts had lower burnout scores than coal miners who worked shift work, which was in line with the results of Zhang et al.'s (53) study involving medical staff, and shift work was a risk factor for burnout. This may be because shift work tends to disrupt the normal daily lives of workers. Irregular work and rest affect the physical and mental health of workers (54).

In this survey on the work content of coal miners, coal miners with a DCR > 1 accounted for 35.9%, which was in line with the survey results of coal miners reported by Han et al. (55). The results of the partial correlation analysis showed that job requirements, occupational stress and occupational burnout were positively correlated, while social support was negatively correlated with occupational burnout. Social support is a moderator of occupational stress, and more social support will reduce the level of job burnout (56–58). The results related to coping styles and job burnout showed that positive coping was negatively related to job burnout, while negative coping was positively related to job burnout, which was consistent with the research results of Sun et al. (59). Bogdan et al. (60) found that the rs5522 locus polymorphism affects functional genetic variation in HPA axis function, and functional genetic variation in HPA axis responses to stress may mediate the risk of mental illness. This study selected the rs5522 and rs2070950 loci of the NR3C2 gene. The results showed that the T allele of the rs5522 locus increased the risk of job burnout (OR = 1.688, 95%CI: 1.057–2.694). The rs2070950 locus of the NR3C2 gene was associated with the occurrence of job burnout, and the CC genotype (OR = 2.792, 95%CI: 1.144–6.812) and C allele (OR = 1.837, 95%CI: 1.258–2.683) increased the risk of burnout among coal miners.

The results of the gene-environment analysis showed that negative coping was the main effect and the best joint effect model consisting of rs5522, rs2070950, DCR, positive coping, and negative coping factors had the greatest degree of effect on burnout, with a cross-validation consistency of (10/10) and a high test sample precision of 0.6722.

The results showed that the NR3C2 gene interacted with occupational strain and coping style, and the more significant interaction combinations at high risk of burnout were moderate negative coping, moderate positive coping, positive for occupational strain, TT genotype at the rs5522 locus of the NR3C2 gene, and CC genotype at the rs2070950 locus of the NR3C2 gene. This was consistent with the results of Wang et al. (61) who found that the interaction term of coping style and job stress had a regression effect on burnout. Further logistic regression analysis revealed that the environment-gene GMDR interaction results were protective factors for burnout in the low risk group compared to the high risk group (OR = 0.103, 95%CI: 0.058–0.182), and the rs5522 and rs2070950 loci of the NR3C2 gene were not interaction main effects, two loci SNPs variants in the interaction increased the risk of burnout. The risk of job burnout in CC/CT^*GG/GC^*occupational stress negative individuals was significantly reduced (OR = 0.254, 95%CI: 0.117–0.555) than in TT^*CC^*occupational stress positive individuals. Suggesting that the interaction of occupational stress with rs5522 and rs2070950 locus influenced the level of burnout occurrence. Compared with TT^*CC^*low positive coping, CC/CT^*GG/GC^*moderate positive coping was a protective factor for job burnout (OR = 0.245, 95%CI: 0.089~0.670). The risk of job burnout in CC/CT^*GG/GC^*high positive coping individuals was lower than TT^*CC^*low positive coping individuals (OR = 0.139, 95%CI: 0.034~0.564). Suggesting that both negative coping and positive coping can interact with the rs5522 and rs2070950 loci of the NR3C2 gene to influence the level of burnout.

Mild, moderate, and severe job burnout were detected among 90% of the coal miners in this study. The incidence of job burnout among coal miners was high and mainly concentrated around mild and moderate burnout. Gender, age, shift work, marital status, positive coping, negative coping, job requirements, and social support influenced the level of burnout.

The prevalence of occupational strain among coal miners with the job requirement-autonomy model was average, and higher levels of occupational strain were associated with a higher probability of burnout; positive coping reduced the risk of burnout, whereas negative coping increased the risk of burnout.

The CC genotype at the rs2070950 locus of the NR3C2 gene was identified as a susceptible genotype for burnout. As for Gene-Environment interaction, the interaction among rs5522 and rs2070950 sites of NR3C2 gene, occupational stress, positive coping styles and negative coping styles could affect the level of job burnout. The occurrence of job burnout is a complex process. On the one hand, the body's exposure to environmental risk factors may increase the risk of job burnout, on the other hand, the existence of gene polymorphism may make individuals carrying susceptible genes less exposed to environmental risk factors can develop burnout. Therefore, the occurrence of job burnout may be the result of the interaction between environmental factors and genes. Coal mine enterprises and higher management units should strive to ensure a safe working environment, and increase the level of coal mine automation, while health management departments should aim to provide better health care. Management personnel should reasonably allocate the working hours and tasks of the workers and provide them with appropriate supports. Coal mine enterprises should formulate a reasonable system, improve the working environment and conditions, and carry out stress management training programs, such as strengthening communication within the organization and offering psychological counseling, so as to effectively reduce the possibility of job burnout by addressing various factors. Workers themselves should also adopt a positive attitude to reduce the possibility of job burnout.

Our study has several important limitations that need to be considered. Firstly, genetic testing was not conducted on all the samples in this study. Therefore, the results obtained from this study need to be validated in a larger sample study. Secondly, there is a limited number of genotypes included in this study, and there are other genes associated with the HPA axis. To better investigate the relationship between job burnout and genetic and environmental factors, a wider range of genotypes will be included in future studies. Lastly, this study utilized a cross-sectional investigation and research method, which allows for only limited information on the occurrence of the disease. To further explore the impact of gene-environment interactions on burnout, establish a network model of genetic environmental susceptibility factors, and delve into the pathogenesis of burnout, cohort studies will be considered in the future.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

This study was approved by the Ethics Committee of Xinjiang Medical University (No.20160218-109). The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.

XL, XM, and FL conceived and designed the study. XL, XM, XY, CQ, and FL contributed to the acquisition, analysis, and interpretation of data, were involved in drafting the manuscript, and revising it for important intellectual content. All authors contributed substantially to the work presented in this paper. All authors reviewed and approved the final manuscript.