Causal inference in environmental epidemiology

Inferring causality is necessary to achieve the goal of epidemiology, which is to elucidate the cause of disease. Causal inference is conducted in three steps: evaluation of validity of the study, inference of general causality, and inference of individual causality. To evaluate validity of the study, we propose a checklist that focuses on biases and generalizability. For general causal inference, we recommend utilizing Hill’s 9 viewpoints. Lastly, individual causality can be inferred based on the general causality and evidence of exposure. Additional considerations may be needed for social or legal purposes; however, these additional considerations should be based on the scientific truth elucidated by the causal inference described in the present article.

Relationship of workplace violence and perpetrators on sleep disturbance-data from the 4th Korean working conditions survey

OBJECTIVE: The present study analyzed relationship of workplace violence and perpetrators of violence on sleep disturbance among wage workers in Korea. METHODS: The present study used data from the 4th Korean Working Conditions Survey (KWCS) of 2014 in selecting a total of 25,138wage workers as the study population, which excluded those who failed or refused to respond to questions required for the present study. The workplace violence experience group included people who satisfied at least one of six relevant criteria (verbal abuse, unwanted sexual attention, threatening or humiliating behavior, physical violence, bullying/harassment, and sexual harassment) and the group was divided according to whether the perpetrator of violence was a client or colleague. Presence of sleep disturbance was determined based on subjective symptoms felt within the past 12 months by each individual. A multiple logistic regression analysis was performed to identify the effects on sleep distance according to general, occupational, and psychosocial characteristics, as well as the types of workplace violence and perpetrators of violence. RESULTS: Workplace violence was found as a factor affecting sleep disturbance (OR = 3.773, 95 % CI = 3.058–4.655), and with respect to perpetrators of violence, complaint of sleep disturbance symptoms was higher when the perpetrator was a colleague or boss (OR = 5.688, 95 % CI 4.189–7.723) than a client (OR = 2.992, 95 % CI 2.301–3.890). CONCLUSION: Workplace violence had an effect on occurrence of sleep disturbance and when the perpetrators of violence was a boss or colleague at work, the risk for symptoms such as sleep disturbance increased, which indicated the need for appropriate intervention from a workplace healthcare perspective, including preventive education of workplace violence among employees.

Risk factors of musculoskeletal symptoms in university hospital nurses

OBJECTIVES: The purpose of this study was to investigate musculoskeletal symptom prevalence in university hospital nurses and explore the relation between musculoskeletal symptom prevalence and work related factors. METHODS: A structured questionnaire was conducted with 620 nurses in a university hospital to look into the characters of responsibility and musculoskeletal symptom prevalence. The questionnaire respondents numbered 534, so the response rate was 86.1%. Among the respondents, three who gave insincere answers were excluded. The final study population was 531 respondents. ANSI Z-365 checklist was applied to look into ergonomic characteristics, and Korean Occupational Stress Scale Short Form was employed to measure job stress. RESULTS: In the case of the whole body, symptom prevalence amounted to 70.8%. Regarding each body region, shoulder symptom prevalence accounted for the highest, or 44.8%, waist 40.7%, and neck 33.3% in order. According to multiple logistic regression analysis, in the case of the whole body, the group with a high ANSI checklist grade had odds ratio of 3.59 (95% CI 1.48 ~ 8.76), and the group with high job stress had 3.19 (95% CI 2.01 ~ 5.07). CONCLUSION: Regarding the occupational factors related to musculoskeletal symptoms of university hospital nurses, it was found that ANSI Z-365 checklist high risk group, total job tenure, department, shiftworks, and job stress had high relation with musculoskeletal symptoms. It is necessary to find an ergonomic solution and a stress reduction plan to prevent musculoskeletal disease.