This study aimed to test two hypotheses: (1) the index of sleep, fatigue and mental workload might reflect and evaluate BPC; (2) there might be a correlation between BPC and the impact of COVID-19. Thus, we verified these hypotheses in civil aviation crews.
As a consequence, it updated the data in civil aviation crews regarding the sleep quality, fatigue and mental workload in the new stage of normalized epidemic era of COVID-19 in China. The insomnia incidence was 49.8%, and gender, position and driving experience had no significant impact. And there was a high level of fatigue, with a 100% incidence reported by participants, which was much higher than that reported by US army aviators [28]. Men were more tired than women. The MWL was reported to be middle level, with a weighted score of 43.1 (SD = 17.5). Furthermore, the older the age and the higher the BMI, the worse the sleep, the more fatigued and higher the mental workload level.
It also first reported here that a comprehensive evaluation of BPC can be made through the assessment index cluster we built. Many studies have reported the effects of sleep quality, fatigue and mental workload on individuals’ memory, attention, reaction, and mental health, which could directly or indirectly respond to brain performance. Yamashita hold the idea [29] that the individuals with attention-deficit/hyperactivity disorder (ADHD) have unstable and unreliable behaviors related to the state of their brains, whereas those without ADHD have an optimal brain state that guides their more stable and reliable behavior. The brain has plasticity. L. L. Beason-Held [30] tested the hypotheses that stable task performance could be supported by stable brain performance or that stable performance could be maintained by changing brain functions if the change was a compensatory reorganization of function. We also found the sleep quality, fatigue and mental workload responded well to BPC. Each indicator contributed greatly to BPC, as there were strong loadings of MWL (loading=-0.7), of PSQI (loading=-0.8), and of MFI (loading=-0.6). As concluded by Walker, Matthew P, et al, the brain under sleep deprivation exhibits inattention, decreased working memory, and insufficient motivation to learn [31]. We also found that the higher the MWL level, the lower the BPC; the worse sleep quality was, the lower the BPC; and the more fatigued an individual was, the lower his or her BPC. These findings may provide new perspectives on how to evaluate BPC.
Additionally, this study highlighted the impact of COVID-19 on civil flight crews. The COVID-19 pandemic has had a profound impact on the aviation industry, leading to job loss, furlough, disruption to careers and training trajectories and uncertainties, even leading to self-harm among airline employees [32]. In addition, there is evidence that COVID-19 induces fears, including fear of infection and fear of passing the infection to others due to ineffective prevention and control measures from the government. Due to the vagaries of the epidemic, people receive nucleic acid tests (NATs) on a fixed schedule or and at any time during the period of normalized control of the epidemic in China. Special occupations in the airlines and health care require not only masks but also personal protective equipment such as gloves, gowns and hats, which is bound to increase the workload of these employees. COVID-19 causes sleep problems such as difficulties initiating and maintaining sleep [33] and fatigue including mental fatigue and physical fatigue [34] to persons. With the statistical analysis of canonical loadings of the COVID-19 set, we also found the self-fear of infection(C1), fear of ineffective prevention and control(C2), physical unwellness caused by NAT(C3), increased workload of personal protective equipment(C4), sleep quality(C5), mental fatigue(C6) and physical fatigue(C7) all contributed greatly to the impact of COVID-19, with a loading of -0.6, -0.7, -0.8, -0.6, -0.9, -0.8 and − 0.8, respectively. The more severe the impact of COVID-19 was, the worse the BPC.
We also explored the relationship between BPC and the impact of COVID-19 with CCA. We found that a moderate positive correlation existed between BPC and the impact pf COVID-19, with a correlation of 0.5. The correlation indicated that the more severe the impact of COVID-19 was on civil aviation crews, the stronger the BPC. However, the pandemic has been in a normalized control period in China. As of 24:00 on November 25, 2021, there had been 860 confirmed cases (including 8 severe cases), 93,087 cured and discharged cases, 4,636 deaths, 98,583 confirmed cases and 4 suspected cases; a total of 1,315,485 close contacts had been traced, and 28,342 close contacts were still under medical observation, according to a report from the National Health Commission of the People’s Republic of China [35]. COVID-19 was still a predictor of BPC. This finding may suggest that there is a long way to go in the fight against COVID-19, and the negative influences should not be underestimated. There are some valid concerns about how to boost the BPC to respond to the impact of COVID-19 on individuals.
This study has limitations that need to be considered:
1) Study setup was a cross-sectional study. So it cannot provide a cause-and-effect relationship. Future study should expand sample size and conduct more rigorous designs such cohort studies.
2) Assessment tools were subjective. Although sleep, fatigue and mental workload were successfully used as evaluation indicators of BPC, the assessment tools in this study were mainly scales that are subjective. Therefore, more evaluation indicators of BPC should be explored and combined with objective evaluation indicators.
3) Statistical methods were exploratory, and associations were hard to define. Although we showed that the relationship between BPC and the impact of COVID-19, we were unable to pinpoint the specific relationship between them. This is a typical drawback of CCA. Future work should seek a mapping method to circumvent this shortcoming.
4) Sample size was small and papulation selection was lack of representative. COVID-19 pandemic affecting all population, all categories, all groups. However, we just investigated the aircrew members with a moderate sample. Future study should expand the simple size and study papulation group.