Shift-Lag and Fatigue
In 1984, shortly after shift change at the Union Carbide Plant in Bhopal, India, poisonous gas was released into the air, killing 6000 people and injuring another 30,000. Even now, almost 25 years later, there is still concern that the ground water is contaminated with mercury. This horrific industrial disaster occurred when night shift workers failed to notice and respond to a culmination of equipment malfunctions. This disaster, along with others including the Three Mile Island Nuclear Power Plant Meltdown, The Exxon Valdez Oil Spill, the Challenger Space Shuttle Explosion and the Chernobyl Nuclear Meltdown and Explosion, is a well known example in which investigation has revealed that fatigue, related to a lack of sleep as a result of changing shifts, contributed.
As progress and invention has made it possible, people are expected to work at all hours of the day. The problem is that we as human beings are not like the machines that we are operating. Our bodies do not function the same at all hours of the day. Instead, our biology dictates, via the circadian rhythm, that we function better during the day than at night. Our brain is a part of this biology; therefore mental performance also is naturally stronger during the day. The circadian clock can be shifted under the right circumstances of light duration, light intensity, temperature and social interactions, however this rarely happens and workers usually do not adapt to night work even after many years of shift work.
When a worker starts an evening or night shift, this usually requires that they end up delaying their sleep time. They usually start the shift in a sleep deprived state. During shift, the circadian clock is demanding sleep, but when the shift is over and even though the worker might be tired, he/she has to fight the circadian rhythm which is set to prevent sleep during the day. The circadian system exerts strong control over the body – even if a night shift worker has slept reasonably well, they are less alert between the hours of 2am and 8am than a day shift worker who for two nights in a row has slept only four hours a night. Rotating shift patterns make it even more difficult for the body to adjust because of the changing and conflicting light-dark exposure and activity-rest behaviour.
As a result, shift workers are often fatigued and suffering from ‘Shift-Lag’, a term used to describe the mental fogginess associated with poor adaptation to shift work. Shift-Lag has various degrees of severity. Mild shift-lag occurs anytime workers are tired, as is typical especially on the graveyard shift, and are trying to keep their eyes open yet are yearning to fall asleep. In this situation, attention to detail suffers, as does reaction time when a problem occurs. Many shift workers also suffer from peripheral hallucinations where the mind detects movement out of the corner of the eye that isn’t there. Shift workers will often have memory problems and have difficulty focussing on a train of thought. Sometimes a worker will experience ‘shift paralysis’ which is the inability to speak or move, even though the person is awake and aware. A milder form manifests when the worker feels able to move but there is a lack of motivation to do so.
It is no wonder that mistakes so often occur on night shifts. Many people have to work shifts and in order to be competitive in today’s market; industry is often required 24 hours a day. There are also professions such as police officers, emergency personnel, doctors and nurses where our very lives depend on their alertness and mental performance. So what can be done? Follow the Shift Health Model and our other recommendations for achieving greater Alertness and Energy.