Field Study of Effects of Night Shifts on Cognitive Performance, Salivary Melatonin, and Sleep

BACKGROUND: Night shift work is associated with many problems such as sleep deprivation, sleepiness, decreased cognitive performance, increased human errors, and fatigue. This study set out to measure cognitive performance, melatonin rhythms, and sleep after different consecutive night shifts (7 vs. 4) among control room operators (CORs). METHODS: The participants included 60 CORs with a mean age of 30.2 years (standard deviation, 2.0) from a petrochemical complex located in Southern Iran. Cognitive performance was assessed using the n-back task and continuous performance test. To evaluate melatonin, saliva was collected and tested by enzyme-linked immunosorbent assay. To assess sleep and sleepiness, the Pittsburgh Sleep Quality Index and Karolinska Sleepiness Scale were used, respectively. RESULTS: Individuals who worked 7 consecutive night shifts had a significantly better cognitive performance and sleep quality than those who worked 4 consecutive night shifts. However, salivary melatonin profile and sleepiness trend were not affected by shift type. CONCLUSION: The main duty of CORs working night shifts at the studied industry included managing safety-critical processes through complex displays; a responsibility that demands good cognitive performance and alertness. It is suggested that an appropriate number of consecutive night shifts in a rotating shift system should be planned with the ultimate aim of improving CROs performance/alertness and enhancing safety.

The Effect of Various Hot Environments on Physiological Responses and Information Processing Performance Following Firefighting Activities in a Smoke-Diving Room

BACKGROUND: Fire service workers often implement multiple duties in the emergency conditions, with such duties being mostly conducted in various ambient temperatures. METHODS: The aim of the current study was to assess the firefighters' physiological responses, information processing, and working memory prior to and following simulated firefighting activities in three different hot environments. Seventeen healthy male firefighters performed simulated firefighting tasks in three separate conditions, namely (1) low heat (LH; 29–31°C, 55–60% relative humidity), (2) moderate heat (MH; 32–34°C, 55–60% relative humidity), and (3) severe heat (SH; 35–37°C, 55–60% relative humidity). It took about 45–50 minutes for each firefighter to finish all defined firefighting activities and the paced auditory serial addition test (PASAT). RESULTS: At the end of all the three experimental conditions, heart rate (HR) and tympanic temperature (TT) increased, while PASAT scores as a measure of information processing performance decreased relative to baseline. HR and TT were significantly higher at the end of the experiment in the SH (159.41 ± 4.25 beats/min; 38.22 ± 0.10°C) compared with the MH (156.59 ± 3.77 beats/min; 38.20 ± 0.10°C) and LH (154.24 ± 4.67 beats/min; 38.17 ± 0.10°C) conditions (p 0.05). Nonetheless, there was a measurable difference in PASAT scores between LH and SH (p < 0.05). CONCLUSION: These consequences demonstrate that ambient temperature is effective in raising the physiological responses following firefighting activities. It is therefore argued that further increase of ambient temperature can impact firefighters' information processing and working memory during firefighting activity.

[ effects of antipronation insole on ground reaction force, impulse and loading rate during one leg landing]

Background and Aim: Measurement of ground reaction forces [GRF] in different physical activities is linked with risk of the injuries of lower limb joints. Insole may alter the amount of these forces. The objectives of this study were to analyze the effects of insole on GRF and time-to peak each reaction force, impulse, and loading rate during landing in normal individuals

Material and Methods: Thirteen healthy male subjects with mean age, mass and height of [21.9 +/- 1.6years], [67.18 +/- 12.6kg], and [175.38 +/- 4.9cm], respectively, participated in this study. Using a Kistler force plates [1000Hz] we measured GRF during landing with and without shoe insole. Then, maximum GRF and their related time-to-peak, impulse and loading rate were measured. Repeated measure ANOVA was used to analyze the data. p<0.05 was considered significant

Results: Wearing insole decreased the peak vertical GRF at the moment of contact of the heel with the ground [P=0.009], peak horizntal GRF [P=0.011] and the loading rate [P=0.01]. But, the vertical impulse increased [P=0.0032]

Conclusion: Reduction of the vertical GRF and loading rate by means of insole may reduce the risk of lower extremity injuries during landing

Evaluation of Related Risk Factors in Number of Musculoskeletal Disorders Among Carpet Weavers in Iran

BACKGROUND: Musculoskeletal disorders (MSDs) are a common problem among carpet weavers. This study was undertaken to introduce affecting personal and occupational factors in developing the number of MSDs among carpet weavers. METHODS: A cross-sectional study was performed among 862 weavers in seven towns with regard to workhouse location in urban or rural regions. Data were collected by using questionnaires that contain personal, workplace, and information tools and the modified Nordic MSDs questionnaire. Statistical analysis was performed by applying Poisson and negative binomial mixed models using a full Bayesian hierarchical approach. The deviance information criterion was used for comparison between models and model selection. RESULTS: The majority of weavers (72%) were female and carpet weaving was the main job of 85.2% of workers. The negative binomial mixed model with lowest deviance information criterion was selected as the best model. The criteria showed the convergence of chains. Based on 95% Bayesian credible interval, the main job and weaving type variables statistically affected the number of MSDs, but variables age, sex, weaving comb, work experience, and carpet weaving looms were not significant. CONCLUSION: According to the results of this study, it can be concluded that occupational factors are associated with the number of MSDs developing among carpet weavers. Thus, using standard tools and decreasing hours of work per day can reduce frequency of MSDs among carpet weavers.

Ergonomics intervention in a tile industry: a case of manual material handling

Manual material handling is one of the major health and safety hazards in industry. This study aims to assess the lifting tasks, before and after intervention using NIOSH lifting equation and Manual Handling Assessment Charts [MAC]. This interventional study was performed in 2011 in a tile manufacturing industry in Hamadan, located in the West of Iran. The prevalence of musculoskeletal discomfort was determined using Nordic musculoskeletal questionnaire. In order to assess the risk factors related to lifting and identify the high-risk activities, MAC and NIOSH lifting equation were used. In intervention phase, we designed a load-carrying cart with shelves capable of moving vertically up and down, similar to scissor lifts. After intervention, the reassessment of risk factors was conducted to determine the success of the intervention and to compare risk levels before and after intervention using t-test. The outputs of MAC and NIOSH lifting equation assessments before intervention revealed that all activities were at high-risk level. After intervention, the risk level decreased to average level. In conclusion, the results of intervention revealed a considerable decrease in risk level. It may be concluded that the given intervention was acceptable and favorably effective in preventing musculoskeletal disorders especially low back pain.

Comparison of ergonomic risk assessment outputs from rapid entire body assessment and quick exposure check in an engine oil company

During the last decades, to assess the risk factors of work-related musculoskeletal disorders [WMSDs], enormous observational methods have been developed. Rapid Entire Body Assessment [REBA] and Quick Exposure Check [QEC] are two general methods in this field. This study aimed to compare ergonomic risk assessment outputs from QEC and REBA in terms of agreement in distribution of postural loading scores based on analysis of working postures. This cross-sectional study was conducted in an engine oil company in which 40 jobs were studied. All jobs were observed by a trained occupational health practitioner. Job information was collected to ensure the completion of ergonomic risk assessment tools, including QEC, and REBA. The result revealed that there was a significant correlation between final scores [r=0.731] and the action levels [r =0.893] of two applied methods. Comparison between the action levels and final scores of two methods showed that there was no significant difference among working departments. Most of studied postures acquired low and moderate risk level in QEC assessment [low risk=20%, moderate risk=50% and High risk=30%] and in REBA assessment [low risk=15%, moderate risk=60% and high risk=25%]. There is a significant correlation between two methods. They have a strong correlation in identifying risky jobs, and determining the potential risk for incidence of WMSDs. Therefore, there is possibility for researchers to apply interchangeably both methods, for postural risk assessment in appropriate working environments