Sleep and the Effects on Shift Workers


New Mexico High School
Supercomputing Challenge
Final Report
April 7, 1999
Team 009
Andress High School

Team Members

Lecroy Rhyanes
Marina Márquez
Carol Díaz
Delilah Monarez


Susie Castro
Leo García

Project Mentor

Joe A. Watts

Table of Contents

Executive Summary


We are team 009 from Andress High School in El Paso, TX. Our team consists of two sophomores, Delilah Monarez and Marina Márquez, and two seniors, Carol Díaz and Lecroy Rhyanes. Being the only team invited from the state of Texas, we decided to investigate a problem that we hoped would be significant from the rest. The title of our project is Sleeping Patterns and the Effects on Shift Workers.

Executive Summary

More than 23 million people work in the United States. Shift work has taken on an important role in our working economy. In addition, it has been incorporated into a number of industries and professions, but only in recent times have we begun to look at its potential long-term health and safety hazards.

We examined the physical and chemical aspects of how the human body has difficulty adjusting to a diverse working schedule. We also researched the health and safety effects of the circadian system and the many physical problems that shift work introduces to the human body. Our plan was to see how shift workers can best cope with their shift work, and enhance their productivity. This project will help society by helping shift workers have a better understanding of how to regulate their sleep/wake patterns and have greater efficiency. Our team has chosen to do this project because it deals with many of the country's important careers such as doctors, nurses, firefighters, policemen, factory workers and convenience store clerks. As a team, we interviewed shift workers, distributed questionnaires, and researched locations such as sleep labs and libraries.

Shift work makes economic sense for capital intensive plants to operate continuously, even though there are the downside risks of night shift operations. Decreased productivity, higher risk of accidents and poorer product quality are all consequences of shift work. However, with the proper training of employers and employees on how shift work corresponds with the human biological time clock, the efficiency of workers and the productivity of companies can be improved. In the future our plan can benefit company owners, shift workers, their families and most importantly, our community.


Shift work is any system of working other than regular day work. With the invention of electricity and the electric light bulb, shift work has become a practical form of employment in the past century. This has broken the routine of past centuries where people rise with the sun and sleep at night. Many people are finding that they are required to work at times traditionally set for rest or home life. As a result of production demands, an estimated 20 to 25 percent of employees undertake shift work in a wide range of industries. Over the past decade, this percentage, particularly in manufacturing and service industries, has increased.

Shift work changes according to a set schedule with many shifts rotating continuously. They can be rotated 24 hours a day, seven days per week, or they can be semi-continuous, rotating two or three shifts per day without weekends. Shift workers who work on the railway on 12-hour shifts, for example, are forced into rotating shifts. Without any choice, this forces the workers to have to take double shifts, which leaves people with very little time off. In these situations, many workers begin to experience problems that deal with social life and recreation, which can complicate the status of their health, both mentally and physically. Therefore, most shift workers look forward to the possibility of slower rotations. Slower rotations are easier to work with since it is the switching of time schedules that makes it more difficult.

Shift workers often function on a schedule that is not natural, leading to an upset of the circadian rhythm. Disorders such as sleep deprivation, gastrointestinal complications, and a disruption of the cardiovascular system are problems that may arise due to these schedules. The threat of night shift work can also bring further trouble to already existing problems, such as disrupted family and social life.


The most important factor of why workers have so many problems with their shift is due to the pattern of their circadian rhythm. The circadian rhythm cycles approximately every 24 hours. There are many indicators of this rhythm but the most evident of these is the core body temperature. As the core body temperature changes, so does the behavior of the worker, which could definitely impact a shift worker's productivity.

The most significant temperature drop of a person's body occurs between 23:00 24:00 (11 p.m. midnight). This course continues until it reaches its peak at about 4:30 a.m. Night shift workers can relate to this, as one tends to feel colder even though the ambient temperature remains the same. When shift workers reach this point they tend to have an uncontrollable urge to go to sleep. There have also been reports of shift workers experiencing "peripheral hallucinations," which is when the shift worker may see things out of the corner of their eyes that are not really there.

From approximately 6:00 6:30 a.m. the body temperature begins to rise as the shift worker sometimes experiences a surge of energy. However, this energy for night shift workers does not last long as the desire to sleep and fatigue associated with night work begins to catch up. Incidents of car accidents for those who drive home in the morning from the night shift tend to occur due to fatigue.

Studies have shown that most night shift workers go straight to bed when they get home. While they are asleep their body temperatures keep rising and reach a peak around 12:00 noon to 13:00 (1 p.m.). This peak in temperature, along with need to go to the wash room, typically wakes a person up. After waking up, sleep tends to become very difficult if not impossible. This is known as sleep maintenance insomnia, which is one of the most frequent complaints of shift workers.

At around 14:00 (2 p.m.) to 17:00 (5 p.m.) the body temperature dips slightly. This is often called the "post lunch dip," but one does not have to eat to get it - it is a natural body rhythm. This most often is the best time for shift workers to try to sleep.

At approximately 20:00 (8:00 p.m.) the body temperature starts to go back up and peaks at around 22:00 (10 p.m.). At this point the body temperature begins to decline again and the cycle repeats itself.

Disruption of the quality and quantity of a regular sleep pattern is common for most shift workers who work at night. Daytime sleep for those who work during late hours is almost never comparable to the deep and refreshing sleep that most have been accustomed to for many years. Difficulty to sleep throughout the day mainly comes from the many daytime disturbances and activities that keep those who try to sleep awake. Being constantly tired is a typical complaint of many shift workers, due to the fact that the circadian rhythms are no longer synchronized, since their sleep patterns are at a continuous change.

Also common among shift workers and night workers are gastrointestinal and digestive problems such as indigestion, heartburn, stomach ache and loss of appetite. Unlike some day-workers, night and rotating shift workers are more likely to suffer from peptic ulcers, due to the improper care of sleep and eating schedules. Given the irregularity in type and timing of meals, it is not surprising that night workers are more likely to have a poor diet. With the exposure to "junk foods" and the consumption of beverages with caffeine the probability of shift workers being able to eat a full, well-balanced meal is not very high.

Shift work is not absolutely associated with cardiovascular diseases. However, heart rate and blood pressure have been slower to follow a circadian rhythm. Since life-style can directly affect an individual's health, it is very important that a shift worker follow exercise programs to maintain an adequate level of fitness. Those that work through the hectic schedules of shift work must avoid smoking and produce good dietary habits. Although it may seem impossible for those on rotating shifts to include leisure activities in their daily routine, it is very important for exercise to be part of their lives.

Studies of Swedish men with a history of heart attacks showed that the majority had been involved in some type of shift work throughout their life. Other studies also conclude that the forward rotations of shift work (Days-Afternoons-Nights) can significantly decrease the levels of several coronary risk factors such as triglycerides, glucose, and urinary excretion of adrenaline from bodily fluids.

Shift workers who are already suffering from an existing condition or disease should also be aware that the medication they take and the functioning of the circadian rhythm could aggravate their status of health. The help of a pharmacist can be helpful in preparing a method where the time and schedule of work can correspond with the taking of medication.

Complaints of shift work and its effect on health becomes more of a problem each day, as reports of its effect on family and social life continue to plague spouses and their children to separations and divorce. This fact is considered very important since the amount and quality of social interaction is related to physical and mental health. Individuals who cannot establish regular routines in their daily activities have difficulties planning for family responsibilities and coping with physical and mental fatigue. Participation in clubs, sports and other organized activities is very difficult since they are usually geared to the normal day schedule. The lack of regular social contact can lead to feelings of loneliness and isolation. In addition, quality child care facilities aimed at meeting the needs of shift workers are almost non-existent.


Due to lack of sleep, the performance level of most shift workers can be extremely low. Without sleep, shift workers tend to experience decreased performance at certain times of the day. The problems that shift workers face each day are not likely to be completely eliminated, but there are practical strategies for improvement.

Overall, there are two basic levels where improvements can be made. The first level is the "Organizational Level," which improves shift schedules and the understanding among employers of what shift work is. The second level is the "Individual Level," which deals with the workers getting more rest, a better diet and reducing stress.

One of the most common approaches in designing a more productive worker is improving the arrangement of the worker's shift schedule and place of work. Good lighting and ventilation are very important on all shifts. Providing good cafeteria services so a balanced diet can be obtained is also very important for shift workers.

Maintaining regular eating patterns is very important for shift workers. Afternoon workers should have the main meal in the middle of the day instead of the middle of the work shift. Night workers should eat lightly throughout the shift and have a moderate breakfast. In these cases the shift worker should not get too hungry while sleeping during the day and digestive discomfort should be minimal. Drinking lots of water and eating a regular balance of vegetables, fruit, lean meat, poultry, fish, dairy products, grains and bread help keep the shift worker away from digestive problems. It is better for the shift worker to eat crackers and fruit instead of carbonated beverages and candy bars during work breaks. Reducing the intake of salt, caffeine and alcohol should also be considered for shift workers. It is also a good suggestion to stay away from greasy foods, especially at night. It is also sensible for the shift worker to relax during meals and allow time for digestion.

Educating shift workers and managers on the potential health and safety effects of rotational shift work can help lessen these effects. In particular, education in stress recognition and reduction techniques is beneficial.

It is beneficial for workers to establish a routine and to make sleep during the day easier. Shift workers may try different patterns of work and sleep to see which is best for them. Having a comfortable, dark, quiet place to sleep during the day for the shift worker ensures a better atmosphere for better sleep. There is also muscle relaxation and breathing techniques that can help sleep and rest. Attention towards general physical fitness and general health habits should be taken seriously.


Overall, our plan to help shift workers cope with their problems and enhance their productivity was achieved. At this moment we are still surveying shift workers in our local areas, but due to inadequate information from the employees we have surveyed we were unable to conclude the results of their status. However, we were able to obtain a large amount of information at sleep labs and libraries to be able to come to a tentative conclusion. The purpose of the program that we were conducting was to record the data from the questions asked in the survey and to research whether their productivity level needed improvement. From the surveys that were completely filled out by employees that worked through 24-hour shifts, we were unable to completely determine their productivity. Many of those workers who worked in these kinds of shifts were young employees who experienced most of their troubles due to their children and their problems academically. The surveys filled out by police officers, for example, were quite helpful due to the age of these officers and the length of time that they have been working. Shift workers who had a more professional occupation such as nurses, police officers and factory workers provided more information than shift workers at a fast food chain or convenience store.


As the only team invited from the state of Texas, we would like to thank the Supercomputing Challenge Committee for allowing us to compete in this wonderful competition.

We would also like to express our gratitude to the following people for supporting us throughout the entire project:


Carol Medley, Shift workers: a descriptive analysis of worker characteristics (College of Administrative science, Ohio State University, 1979) p. 1-18.

David R. Morgan, Sleep secrets for shift workers and people with off-beat schedules (Whole Person Associates, c1996) p. 98-145.

J. Hedges and E. Slekscenshi, Workers on late shifts on a changing economy (Washington: Department of Labor, Bureau of Labor Statistics, 1980) p. 11-21.

Crystal E. Cruz, Sleep Patterns in air traffic controllers working rapidly rotating shifts (Washington, D.C.: Office of Aviation Medicine, U.S. Department of Transportation 1996) p. 14-18.

Md. Bethesda, Sleep apnea: is your patient at risk? (National Institutes of Health, 1995) p. 41-78.


Welcome to our shift worker survey! We are students from Andress High School, and are working on a project dealing with shift workers. We ask that you answer these questions truthfully land honestly. Please try to be as exact and as specific as possible. Your answers are critical to our project. Thank you for your time and cooperation.

   1.   What is your age?
   2.   Gender:
   3.   What is your occupation?
   4.   How may weeks have you been on your current shift?
   5.   How often, in weeks, is your shift rotated?
   6.   What time do you clock in during your current shift?
   7.   What time do you clock out during your current shift?
   8.   How many days in a week do you usually work?
   9.   How many hours of sleep do you usually get in a day?
   10.  Do you ever have difficulty sleeping?
   11.  If so, what do you think accounts for your difficulty of falling asleep?
   12.  How many hours after your shift has started do you feel the least alert?
   13.  Have you ever been in any accidents that you feel or know
        have been caused by you not being able to get the amount of
        sleep necessary for you due to your work shift?
   14.  If so, how may accidents have you been involved in? 
   15.  How many hours in a week do you exercise?
   16.  In a scale of 0-8, what is your daily intake of:
        (0 being no intake and 8 being maximum intake)
            Fruits and Vegetables
            Sugar and Fat (ex: carbonated beverages, candy, caffeine products, etc.)
            Fluids (ex: water, juices, milk, etc.)

   17.  Do you snack during your shift?
   18.  If so, are your snacks sodium or sugar based?
   19.  What times during your shift do you snack?  If it is during
        your break please tell us what time you take your breaks. 
   20.  Do you feel more or less alert after you snack on your shift?  If so, please explain. 
   21.  Do you suffer from any medical illnesses that you feel are caused by your working schedule?
   22.  If so, what illnesses: (please check all that apply and specify the problem in the space provided.)
         ___ gastrointestinal problems (ex. Heartburn, indigestion, diarrhea, etc.)
         ___ cardiovascular problems (ex. Heart problems, etc.)
         ___ sleeping disorders (ex. Insomnia, sleep apnea, etc.)

         ___ other illnesses