The Relationship Between Occupational Stress And Hypertension In Xinjiang Arid Desert Oil Workers

Objective: To investigate the general condition of occupational stress, mental health,muscle injury and physical health among workers at oil field in desert in Xinjiang Province. Prospective cohort study was used to analyze the correlation and causal relationship between occupational stress and hypertension. The effect of gene polymorphism of Gene GR and β₂-AR on hypertension caused by occupational stress was also investigated. The study also aimed at exploring the effect of epigenetics on the correlation between occupational stress and hypertension by means of comparing the degree of DNA methylation at Gene ADD1 promoter between hypertension group and control group. Our study provided epidemiological information on occupational stress and hypertension among workers at oil field, thus providing scientific basis for strategies of improving workers’ mental health and preventing hypertension. Methods: 1) Stratified cluster sampling was applied. Occupational Stress Inventory Revised Edition（OSI-R）,Cost-Payment Unbalance Inventory, Self-rating Symptom Scale, Self-Rating Depression Scale, Self-rating Anxiety Scale, Muscle Injury Scale were used. The survey was undertaken among a total of 4370 workers; 2) The characteristics of 1280 randomly chosen workers from 3 oil fields were used as baseline characteristics. The workers were followed up for 2 years so that the effect of occupational stress on hypertension was analyzed; 3) Polymerasechain Reaction-restriction Fragment Length Polymorphism（PCR-RFLP） was used to determine gene polymorphism of GR and β₂-AR for 179 workers with hypertension（patient group） and 179 workers without（control group）. The subjects were matched based on gender, age（±3） and race; 4) The DNA were sequenced using hydrosulphite cloning sequencing. Then PCR were performed with BSO primer.Then sequencing was performed to determine whether methylation occurred at CpG of ADD1. Results: 1) A total of 4500 questionnaires were provided, and 4370 validated ones were collected. The validation rate was 97.11%; 2) The score of occupational stress was different by gender, race, education level, length of service, type of work, title（P<0.05）;race is not significant（P>0.05）; 3) The score of extrinsic effort and work reward was different by length of service, education level, type of work, title（P<0.05）; 4) The score of SCL-90, SDS, SAS were different by race, age, length of service, title, and marital status（P<0.05）. The ORQ was positively correlated with PSQ, SDS, SAS, SCL-90. The PRQ was negatively correlated with SDS, SAS, SCL-90. As the level of occupational stress increased, absence rate increased as well, and the absence rate among high-cost-low-payment workers increased; 5) A total of 4370 workers were included,83.29%of which experienced muscle injury. Among them, 80.25%workers injury in back or waist; 70.96%workers experienced injury at neck and shoulder. The level of injury at back and neck was different among workers with different levels of stress（P<0.05）. The score of WAI was lower in workers with injury as mentioned above. Logistic regression was used to analyze the effect on muscle injury and indicated that gender, nationality,salary, occupational stress, SCL-90, ERI, WAI was significant; 6) The study found that the incidence of hypertension was the highest. The level of blood glucose was positively correlated with occupational stress, which indicated that blood glucose increased as occupational stress worsened; 7) hypertension: 1080 workers were included into the cohort. 85 workers were censored when the follow-up ended. 995 oil workers were followed up, with hypertension occurring in 193 workers. The incidence was 19.4%.Major risk factors included age, habit（smoking, drinking alcohol, BMI）, occupational stress（occupational role strain, personal strain）, cost-payment imbalance; 8) With other factors controlled, the risk of hypertension in group with low-high occupational stress（low at beginning of cohort and high at end of follow-up） was 2.687 times higher compared with that in low-low group（low at beginning of cohort and low at end of follow-up）. The risk of hypertension in group with high-high occupational stress was2.970 times higher than that in low-low group. The risk of hypertension in group with low-high personal strain was 2.141 higher than that in group with low-low group. The risk of hypertension in group with high-high person strain was 3.907 times higher than that with low-low personal strain; 9) With occupational role controlled, the incidence of hypertension decreased by 14.35%, 13.26%, 11.52%, 17.84%in group with low-high,high-high occupational stress and group with low-high, high-high personal strain,respectively; 10) The distribution of GR Bcl I, β₂-AR 46A/G, β₂-AR Gln27 Glu was different between group with and without hypertension（P < 0.05）. The risk of hypertension increased in group with CG+GG at GR Bcl I（OR=0.454, 95% CI=0.206⁰.995）; the risk of hypertension increased in group with AG+GG at 46A/G of β₂-AR（OR=0.332, 95% CI: 0.150⁰.735）; 11) Using GMDR software, the interaction between GR Bcl I and β₂-AR 46A/G was significant; the interaction between occupational role strain and GR Bcl I was significant; 12) The distribution of CpG3, CpG5 and CpG10 of ADD1 was different between hypertension group and control group（P<0.05）. Among hypertension workers, the distribution of CpG3, CpG5 of ADD1 was different between group with high-and mid-occupational role strain and that with low-occupational role strain（P<0.05）. Conclusions: 1) The score of occupational stress in workers at oil field was higher than the national norm, higher in male than female, inminorities than Han nationality. The level of occupational stress was higher in spudder with college diploma,less than 10 years’ length of service, junior title. The sense of cost-payment imbalance was more severe in underground workers, as length of service, title, salary increased, the sense of imbalance became more severe; 2) The average level of psychological abnormality,anxiety, depression was higher inminorities than Han nationality. Workers aged between30 and 45, 10-20 years’ length of service experienced the worst mental health, and most severe anxiety and depression. Spudders with senior tile experience more anxiety,psychological abnormality and depression. Workers with divorce or bereft of his spouse has high level of depression. The incidence of anxiety and depression increased as occupational stress increased. So was absence rate. Nervous reaction was one risk factor for anxiety, depression and mental health problem; 3) As the level of occupational stress increased, the incidence of injury in back, waist, neck and shoulder increased. The incidence of injury also increased in workers with cost-payment imbalance; 4) The incidence of hypertension was the highest. The level of blood glucose was higher in workers with high level of occupational stress than those with mid or low level. The blood glucose increased as the level of occupational stress increased. The level of blood glucose was positively correlated with occupational stress and personal strain; 5) The incidence of hypertension increased as age increased and level of occupational stress increased. the major risk factor included age, habit（smoking, drink alcohol, BMI）, occupational stress and cost-payment imbalance. The risk of hypertension was higher in group with increased level of occupational stress and with increased level of personal strain. The risk of hypertension was higher with higher level of occupational stress. It is of great public health significance to control the level of occupational stress in order to decrease the incidence of hypertension. Susceptible genotypes of hypertension included CG+GG of GR Bcl I, AG+GG at β₂-AR 46A/G. The model of interaction between GR Bcl I and β₂-AR46A/G and the interaction between occupational stress and GR Bcl I was optimalcombination of gene-gene and gene-environment, respectively. The level of methylation CpG3, CpG5, CpG10 was higher in hypertension group than that in control group. The level of methylation CpG3, CpG5, CpG10 was lower in group with low level of occupational strain among hypertension group, which indicated that lower level of methylation of promoter of ADD1 might increase the risk of primary hypertension. The level of methylation in ADD1 modifies the correlation between occupational stress and hypertension.