Deleterious Effects of Shift Work in the Realm of Cognitive and Behavioral Domains : A Critical Review

Shift workers experience a disruption in the circadian sleep-wake rhythm, which brings upon adverse health effects such as fatigue, insomnia and decreased sleep quality. Moreover, shift work has deleterious effects on both work productivity and safety. In this review, we present a brief overview of the current literature on the consequences of shift work, especially focusing on attention-associated cognitive decline and related behavioral changes. We searched two electronic databases, PubMed and RISS, using key search terms related to cognitive domains, deleterious effects, and shift work. Twenty studies were eligible for the final review. The consequences of shift work can be classified into the following three categories extracted from the literature review : 1) work accidents ; 2) commuting accidents such as car accidents that occur on the way to and from work ; and 3) attendance management at work (i.e., absenteeism, tardiness, and unscheduled early departure). These cognitive and behavioral consequences of shift work were also found to be associated with sleep disorders in shift workers. Thus, improvements in the shift work system are necessary in order to enhance workers' health conditions, work productivity, and safety.

Animal Models of Demyelination and ¹H-Magnetic Resonance Spectroscopy

The proton magnetic resonance spectroscopy (¹H-MRS) is a tool used to detect concentrations of brain metabolites such as N-acetyl aspartate, choline, creatine, glutamate, and gamma-amino butyric acid (GABA). It has been widely used because it does not require additional devices other than the conventional magnetic resonance scanner and coils. Demyelination, or the neuronal damage due to loss of myelin sheath, is one of the common pathologic processes in many diseases including multiple sclerosis, leukodystrophy, encephalomyelitis, and other forms of autoimmune diseases. Rodent models mimicking human demyelinating diseases have been induced by using virus (e.g., Theiler's murine encephalomyelitis virus) or toxins (e.g., cuprizon or lysophosphatidyl choline). This review is an overview of the MRS findings on brain metabolites in demyelination with a specific focus on rodent models.

Firefighters and Posttraumatic Stress Disorder

Occupational hazards of firefighting and rescue works include frequent exposure to emergencies and life-threatening situations. These stressful work conditions of being constantly under pressure and exposed to potentially traumatic events put them at higher risk of developing posttraumatic stress disorder (PTSD), compared to the general population. PTSD is a potentially debilitating mental disorder, due to persistent intrusive thoughts, negative alterations of mood and cognition, hypervigilance, avoidance of similar situations and reminders, and re-experiences of the traumatic event. Previous studies have shown a relatively high prevalence of PTSD among firefighters, indicating the need for a systematic approach of early detection and prevention. Therefore, a critical review of the current literature on PTSD in firefighters would provide valuable insights into developing effective prevention and intervention programs. Literature indicated that there are risk factors of PTSD in firefighters, such as pre-existing depression, anxiety, sleep disorders, occupational stress, physical symptoms, and binge drinking, whereas social support and adequate rewards are protective factors. Although there are differences in the prevalence of PTSD across studies, partly due to various assessment tools utilized, different sample sizes, and sample characteristics, over one tenth of the firefighters were estimated to have PTSD. The current review warrants further investigations to precisely assess PTSD and co-morbid mental disorders, functional outcomes, and associated factors, and to develop evidence-based preventive and interventional programs to help firefighters with PTSD.

Parkinson's Disease among Firefighters : A Focused Review on the Potential Effects of Exposure to Toxic Chemicals at the Fire Scene

Previous studies have found that firefighters have a tenfold higher prevalence of Parkinson's disease (PD) compare to the general population. Firefighters are constantly exposed to various occupational hazards including toxic chemicals of fire residue and the toxic chemicals can effects development and progression of PD. Nevertheless, there were no studies about the association between exposure to chemical byproducts of combustion and the development of PD among firefighters. Thus the aim of this study is to look into existing researches regarding the effect of chemical byproducts of combustion on the development of PD. An extensive literature search was conducted to identify harmful chemical components of smoke and fire residue, using the PubMed database during November of 2016. We searched for relevant articles by combining several keywords that contained “Parkinson's disease” and each of the different toxic chemicals, yielding a total of 1401 articles. After applying the selection criteria, 12 articles were chosen. Chemical substances reported to have a harmful effect on PD, in at least one article, were carbon monoxide, toluene, manganese and lead. Carbon monoxide and metal substances including manganese and lead were found to be associated with an increased PD risk in more than two articles. There was a heightened risk of PD in firefighters due to exposure of chemical byproducts of combustion including carbon monoxide, toluene, man-ganese and lead. However, to the best of our knowledge, to support this result we need more systematic epidemiological studies about these risk factors of PD among firefighters. In addition, further studies for the effects of prolonged exposure to toxic fire residue on the development and progression of PD in firefighters are needed.

Reliability and Validity of the Korean Version of the Post-Traumatic Stress Disorder Checklist in Public Firefighters and Rescue Workers

OBJECTIVES: Firefighters and rescue workers are likely to be exposed to a variety of traumatic events; as such, they are vulnerable to the risk of post-traumatic stress disorder (PTSD). The psychometric properties of the Korean version of the PTSD Checklist (PCL), a widely used self-report screening tool for PTSD, were assessed in South Korean firefighters and rescue workers. METHODS: Data were collected via self-report questionnaires and semi-structured clinical interviews administered to 221 firefighters. Internal consistency, item-total correlation, one-week test-retest reliability, convergent validity, and divergent validity were examined. Content validity of the PCL was evaluated using factor analysis and receiver operating characteristic (ROC) analyses were used to estimate the optimal cutoff point and area under the curve. RESULTS: The PCL demonstrated excellent internal consistency (alpha = 0.97), item-total correlation (r = 0.72-0.88), test-retest reliability (r = 0.95), and convergent and divergent validity. The total score of PCL was positively correlated with the number of traumatic events experienced (p < 0.001). Factor analysis revealed two theoretically congruent factors: re-experience/avoidance and numbing/hyperarousal. The optimal cutoff was 45 and the area under the ROC curve was 0.97. CONCLUSIONS: The Korean version of the PCL may be a useful PTSD screening instrument for firefighters and rescue workers, further maximizing opportunities for accurate PTSD diagnosis and treatment.

Longitudinal Cerebral Perfusion Changes in Parkinson's Disease with Subjective Cognitive Impairment

BACKGROUND AND PURPOSE: Although subjective cognitive impairment (SCI) is often accompanied by Parkinson's disease (PD) and may predict the development of mild cognitive impairment or dementia, longitudinal brain perfusion changes in PD patients with SCI remain to be elucidated. The current prospective study examined cerebral perfusion changes in PD patients with SCI using technetium-99m hexamethylpropylene amine oxime single photon emission computed tomography (SPECT). METHODS: Among 53 PD patients at baseline, 30 patients were classified into the PD with SCI group and 23 patients were assigned to the PD without SCI group. The mean follow-up interval was 2.3±0.9 years. The Mini-Mental State Examination, Clinical Dementia Rating, and Global Deterioration Scale were used to assess impairments in cognitive function. Brain SPECT images were acquired at baseline and follow-up. RESULTS: Significant differences between the two groups were not found for demographic variables, PD severity, or cognitive function at either baseline or follow-up. At baseline, the PD with SCI group showed decreased perfusion in the left angular gyrus compared to the PD without SCI group. Longitudinal analysis revealed widespread perfusion reductions primarily in the bilateral temporo-parieto-occipital areas and cerebellum in the PD with SCI group. Relative to the PD without SCI group, an excessive decrease of perfusion was found in the left middle frontal gyrus of the PD with SCI patients. CONCLUSIONS: Our findings suggest that perfusion deficits in the middle frontal area may play an important role in the pathophysiology of SCI in PD.

Advances in Functional Connectomics in Neuroscience : A Focus on Post-Traumatic Stress Disorder

Recent breakthroughs in functional neuroimaging techniques have launched the quest of mapping the connections of the human brain, otherwise known as the human connectome. Imaging connectomics is an umbrella term that refers to the neuroimaging techniques used to generate these maps, which recently has enabled comprehensive brain mapping of network connectivity combined with graph theoretic methods. In this review, we present an overview of the key concepts in functional connectomics. Furthermore, we discuss articles that applied task-based and/or resting-state functional magnetic resonance imaging to examine network deficits in post-traumatic stress disorder (PTSD). These studies have provided important insights regarding the etiology of PTSD, as well as the overall organization of the brain network. Advances in functional connectomics are expected to provide insight into the pathophysiology and the development of biomarkers for diagnosis and treatment of PTSD.