In general, our findings are consistent with previous studies involving different populations [14,17,24–26]. A previous study conducted in a Danish general working population reported higher odds of work-related stress such as conflicts at work and low decision latitude among non–day workers compared with day workers . Another epidemiological investigation was conducted among employees in the United Kingdom oil and gas industry, including those who worked on oil and gas offshore installations and onshore processing plants . Researchers found that onshore shift workers had a significantly less favorable work environment including physical stressors, job demand, job control, skill discretion, supervisor support, and safety perceptions than day workers. Nabe-Nielsen et al  found that job demand, decision latitude, skill discretion, and supervisor support were lower in evening and night shift workers compared to day shift workers in a Danish eldercare sector. Previous studies also found that the nurses working non–day shifts have more work–family conflicts than those working day shifts [25,26].
The significant differences in the total number of stressful events that occurred in the previous month and year between non–day shift and day shift workers in the current study could be caused by differences in the intensity of work. The difference could also be caused by work content. The significant difference in the number of physical/psychological threats might illustrate that the job content was different across shift, and this difference might contribute to the difference reported for the administrative/professional pressure across shift. For example, the officers working on non–day shifts encountered significantly more physical/psychological threat-related events such as “responding to a felony in progress” and “dealing with family disputes and crisis situations”, and subsequently, they would also have a higher frequency of “court appearances on their day off or day following a night shift”, “experiencing negative attitudes toward them”, and “insufficient manpower to adequately handle a job”. Therefore, they might need a higher level of administrative and organizational support, and support from family, friends, and the WEHI-539 Supplier they served. However, these needs might not be seen from the administrators\’ perspectives . The significantly fewer number of administrative and executive officers working on non-day shifts in the current study may provide evidence in support of this possibility. Furthermore, these unmet needs might be associated with the increased number of other stressors such as “fellow officers not doing their job” and “demands made by family for more time”. It would be worthwhile to investigate whether police officers working on non-day shifts encounter a higher number of stressful events in other agencies that have different supervising strategies and administration levels.
There may be an expectation that the main source of police work-related stress would be from physical/psychological threats. However, our findings showed that the police officers reported a higher frequency of administrative/professional pressure than physical/psychological threats. Most of the stressors police officers encountered in the previous month and year were not related to physical/psychological threats. This finding was consistent with a previous study showing that administrative/professional pressure was most frequently occurring among the three subscales of police stress . Because physical/psychological threats are an inherent part of police work, there is relatively little that can be done to reduce their occurrence in the police workforce. However, it may be possible to reduce or eliminate many of the administrative and organizational stressors within a police department.
Our study differed from previous investigations in the way stress was measured. Boggild et al  used a questionnaire that was constructed from 23 questions to assess work-related psychosocial job demands, decision latitude, social support, conflicts, and job insecurity in a random sample drawn from the Central Population Register of Denmark . Parkes  assessed perceived stress related to work environment in six dimensions taken from six questionnaires. In a health care sector, work demands, control, and support were measured using a different questionnaire . Using different questionnaires in different studies may be reasonable because work stress may vary by occupational characteristics. However, whether these questionnaires were ideal to assess the specific work stress in the study population was not clear. The Spielberger Police Stress Survey questionnaire  used in our study was specifically designed for assessing police work-related occupational stress, and therefore, providing unique information involving police stress.