Human beings, like any other living beings, have an internal body clock that regulates biological cycles, including sleep-wake cycle. The majority of these cycles last close to 24 hours (Circadian) and are ready to synchronize with the daily environment, light-darkness rhythm, being able to be active and awake during the day, and to sleep and rest at night, which coincides with a decrease of body temperature that starts during the last hour of the day. When a person works at night, or has rotational shifts, the Circadian system does not manage to adapt quickly to the new schedule, and this results in a desynchronizing between the biological rhythm and the schedule external demands.
Nowadays, work demands are higher and higher due to increased competitiveness in the market and the need to achieve production objectives, which is a major reason why company operations go round the clock and workers do fixed or rotational night shifts; during these shifts, there is sleepiness during working hours, which involves an increased risk of having a work-related accident.
Those who work night shifts sleep four to six hours a day on average; if they also suffer from a rotational shift-related sleep disorder, sleep average is reduced to less than five hours. These people, under controlled optimal environmental conditions, can only achieve a six-hour daytime sleep, even though they could sleep longer.
Shift rotation at work is a reality and results in negative consequences for the health of workers; these effects are caused by two essential mechanisms: the disruption of the biological rhythms and sleep deprivation. Because of these, health-related conditions occur more intensely in rotational and night shifts, as evidenced by the prevalence of gastric ulcers, an undisputable biological marker of stress. This pace of work is also associated with the decrease of the immune response, the increase of cardiovascular risk, the development of metabolic disorders, reproductive problems, and the increase of accidents at work, among others.
Shift work sleep disorder, also known as sleep disorder secondary to shift-rotation work, is clinically expressed by insomnia or excessive sleepiness, accompanied by a reduction in sleep total (one to four hours) and in sleep efficiency, poor sleep, a reduced level of alertness, and deficient work performance associated with a work schedule that overlaps sleep regular hours.
According to some research, the prevalence of this disorder is estimated in 20% in developed countries, of which 5% is sympto-matic. A number of complications due to shift work sleep deprivation have been described, among them mood swings, social isolation, little interaction with coworkers, depression, risk of substance abuse, making mistakes or having accidents at work, and car accidents, along with worsening of health due the development or exacerbation of gastrointestinal, metabolic, neoplastic, or cardiovascular conditions. In addition, there is higher risk of suffering from cardiovascular conditions, digestive disorders, obesity, psychological disorders, chronic fatigue, insomnia, and sleepiness.
It has also been reported that most workers consider that the characteristics of their night work not only alter their sleep, but also create difficulties in their family life, restrict their social life, decrease their leisure activities and affect their health negatively; sleep alterations are one of the main problems this type of workers face.
In Mexico, the community of specialists in sleep disorders must work together with entrepreneurs and work authorities to suggest laws aimed at decreasing excessive daytime sleepiness and at increasing sleep quality in order to improve the safety conditions at work for employees with rotational work, such as construction workers, nurses, drivers, security staff, since this would ultimately benefit the safety and health of workers.
We are conducting research with the patients at the Sleep Disorders Clinic of the Universidad Autónoma de México (UNAM) in order to compare the subjective quality of sleep to the polysomnographic variables of the population with Obstructive Sleep Apnea (OSA) who have rotational shift jobs and those with daytime shifts.
The method used was a retrospective and comparative study with a sample of 107 male participants distributed in three groups: Group A was formed by subjects with severe-intensity OSA who work during the day, B was formed by severe-intensity OSA who work rotational shifts, and C was the control group.
The polysomnographic studies were conducted at the Sleep Disorders Clinic of UNAM.
The sleep quality subjective variables were night awakenings, electroencephalographic activations, sleep hours during weekdays, sleep apnea rate, Epworth sleepiness scale score, oxygen saturation, and nap length.
The preliminary results of this first stage of the investigation show that the assessment of sleep architecture in subjects with OSA did not produce any differences; however, there were statistically significant differences in the respiratory variables, micro-awakenings, and subjective assessment of sleep among these subjects related to a difference in the number of sleep hours (NHS). Finally, it is important to point out that the effects of sleep deprivation due to rotational shift work and the presence of OSA deserve to be included in future investigations.
Ivonne Selenne Verde Tinoco
Health Promotion specialist from Universidad Aútonoma in Mexico City.
CPAP Clinic Manager, in charge of the assistance of and follow-up with
patients with respiratory disorders at the Sleep Disorders Clinic of UNAM, Hospital General de México facilities, which has conducted research in shift work sleep disorders.