Very Long (> 48 hours) Shifts and Cardiovascular Strain in Firefighters: a Theoretical Framework

Shift work and overtime have been implicated as important work-related risk factors for cardiovascular disease (CVD). Many firefighters who contractually work on a 24-hr work schedule, often do overtime (additional 24-hr shifts) which can result in working multiple, consecutive 24-hr shifts. Very little research has been conducted on firefighters at work that examines the impact of performing consecutive 24-hr shifts on cardiovascular physiology. Also, there have been no standard field methods for assessing in firefighters the cardiovascular changes that result from 24-hr shifts, what we call "cardiovascular strain". The objective of this study, as the first step toward elucidating the role of very long (> 48 hrs) shifts in the development of CVD in firefighters, is to develop and describe a theoretical framework for studying cardiovascular strain in firefighters on very long shifts (i.e., > 2 consecutive 24-hr shifts). The developed theoretical framework was built on an extensive literature review, our recently completed studies with firefighters in Southern California, e-mail and discussions with several firefighters on their experiences of consecutive shifts, and our recently conducted feasibility study in a small group of firefighters of several ambulatory cardiovascular strain biomarkers (heart rate, heart rate variability, blood pressure, salivary cortisol, and salivary C-reactive protein). The theoretical framework developed in this study will facilitate future field studies on consecutive 24-hr shifts and cardiovascular health in firefighters. Also it will increase our understanding of the mechanisms by which shift work or long work hours can affect CVD, particularly through CVD biological risk factors, and thereby inform policy about sustainable work and rest schedules for firefighters.

The Effects of Working Hours on Nerve Conduction Test in Computer Operators

Background: Long hours of work at a computer can result in potential adverse effects such as pain, paraesthesia, and subjective weakness of upper extremities with associated decreased nerve conduction velocities of peripheral nerves (median and ulnar). Objective: To determine whether repetitive tasks performed for long hours by computer operators can lead to peripheral neuropathy as measured by nerve conduction studies of upper extremities. Material And Methods: We performed nerve conduction tests on 50 computer operators in two study groups. Group I consisted of computer operators who worked a minimum of 6 hours per day at the computer while Group II worked a maximum of 2 hours per day. Results: Significant differences were observed between groups for most physical signs. In addition, there were significant differences between the groups for nerve conduction velocities of the medial (motor & sensory) and ulnar (motor & sensory) nerves. Conclusion: We found symptoms of pain, paraesthesia and subjective weaknesses as well as decreased conduction velocities of peripheral nerves in computer operators who work long hours. Further nerve conduction studies are needed to confirm predictive value for the development of carpal tunnel syndrome.

An Association between Working Schedules and Depression in Public Sector Employees / 대한산업의학회지

OBJECTIVES: This study determined the work schedules of public project workers who work an irregular shift and assessed the effect of these schedules on depression. METHODS: Study subjects were 2934 laborers who are members of seven labor unions. Each was given a questionnaire requesting basic personal information, habits, socioeconomic status, and work schedules. Information gathered on work schedules included daytime, nighttime, and weekend work hours. Depression was evaluated using the Beck Depression Inventory (BDI), with Laborers who checked "not depressed" and "slightly depressive" categorized to a low-risk group, whereas laborers who checked "depressed" and "severely depressed" were categorized to a high-risk group. We used the Chi-square test and multivariate logistic regression to examine associations between work schedules and depression. RESULTS: Laborers on an irregular work schedule averaged 47.8 hours/week and laborers who working over 48 hours/week comprised over half (54.5%) of the total population. Laborers performing night work, Sunday work, and Saturday work more than once in a month made up 25.7%, 30.8% and 33.5% of the examined population, respectively. A high-risk for depression was identified in 10.4% of laborers. Using logistic regression, depression was statistically associated with working : over 10 hours a day (OR=1.63, 95% CI 1.10~2.43), night work (OR=2.20, 95% CI 1.46~3.32), Sunday work (OR=1.81, 95% CI 1.15~2.85) and Saturday work (OR=1.82 95% CI 1.18~2.82). CONCLUSION: A significant number of laborers with irregular working shifts work long hours and on weekends. Depression was significantly associated with this type of work schedule.