The effects of shift work on circadian I an rhythms has become a subject of great Interest to many industries, hospitals, and sleep researchers. More and more recognition is being given to the results of these studies, especially the possible adverse effects on those working the night shift or a shift they are unable to adapt to adequately. Only a few of these studies, however, have been conducted on registered nurses, a major group involved with shift work.

The purpose of the present study was to investigate the effects on nurses working the a.m. shift (7 a.m. to 3:30 p.m.), the p.m. shift (3 p.m. to 11 :30 p.m.), and the night shift (11 p.m. to 7:30 a.m.) full-time. In addition, a fourth study group was Included, namely, the part-time night shift. All four of these groups were studied in regard to performance, mood, and temperature. Urine specimens were collected and analyzed for sodium and potassium content on the two night-shift groups. The study was conducted for a minimum of five working days with at least one day off among them for all the full-time groups, and data were collected for up to two weeks in the part-time night-shift group.

This study is of a correlational, comparative type. The subjects were divided into four groups: Group 1 , the a.m. group (N=9); Group II , the p.m. group (N=6); Group III, the full-time night-shift group (N=6); and Group IV, the part-time night-shift group (N=5). Subjects were admitted into the study when they met the criteria for selection, were willing to participate, and worked an appropriate schedule to fit the study time.

The data were analyzed according to cosine fit, standard deviation, and angular standard deviation and mean with a computer program which was 360° to fit the 24-hour clock. Seven null hypotheses were researched. Chi-Square tests were run on the demographic data, and an analysis of variance on the math scores (performance) and mood test scores was made. In all the areas investigated some differences and trends were found among the groups. The following is a list of the results of the null hypotheses tested.

  1. No significant difference was found in the performance of mathematical tasks when the scores of the four groups were compared.
  2. No significant difference was found between the different shift patterns regarding tension-anxiety as measured by the Profile of Mood States (POMS) test.
  3. No significant difference was found between the different shift groups regarding depression-dejection as measured by the POMS test.
  4. No significant difference was found between the four groups regarding anger-hostility as indicated by the POMS test.
  5. No significant difference was found between the different shift patterns regarding vigor as indicated by the POMS test.
  6. The p value was p=.056 for fatigue as measured by the POMS test when the four groups were compared.
  7. No significant difference was found between the different shift patterns regarding confusion-bewilderment as indicated by the POMS test.

In reference to the hypotheses list, the a.m. shift did worse over all on the performance examinations (math). The p.m. shift and full-time night shift did the best on the basis of an analysis of variance; however, none of the differences was significant. All four groups had temperature mean peaks which were reasonable for the shifts the subjects in those groups worked. The a.m. shift's temperatures peaked most often on a day off, while those of the other three groups peaked more often on a working day. No tests of significance were done on the temperature readings.

The mood tests were given to each subject at the beginning of each shift. The two night-shift groups (III and IV) reported having the highest amount of tension, depression, anger, fatigue, and confusion. The p.m. group (II) reported the most vigor. An analysis of variance was done on all these variables in the Profile of Mood States test. The fatigue scores were the only ones found to approach significance (p=.056).

Urine samples were collected and temperature readings were taken simultaneously every three hours by both night groups (III and IV) while the subjects were awake. These were analyzed for sodium and potassium content. In Group III, most of the subjects had their peak within two to three hours of one another. In Group IV, however, the sodium readings varied greatly and peaked several hours earlier in the day than they did in the subjects in Group III. The potassium readings varied widely between individuals.

Chi-square was done on the demographic data of age, ethnic back ground, marital status, children, average number of hours of sleep obtained on a day off, and average number of hours slept on a day worked. The first four were not significant at the 5 percent level of significance. The average number of hours of sleep on a working day had a p value of .056 and on a day off of .037.

On the basis of the results of this study, the following recommendations were made: that a similar study be made, but with matching groups and with more subjects in each group, and that the project be carried on for a longer period of time. it was also suggested that different tools be used, for example, a different mood test and a different test for performance. It was recommended that the urinary sodium and potassium tests should be done on more subjects, preferably on all subjects participating. Also, a larger number of variables could be included for study, such as heart rate, blood pressure, respiratory rate, and urinary cortisone levels.

The implications for nursing include the relevance of this study for both the staff nurse in a hospital setting and the administrative nurse who is responsible for scheduling and hiring nurses. The staff nurse can be aware of her own circadian rhythms and of the possible effects of working various shifts (e.g., the increase in fatigue of those working the night shift). She can also be aware that other related studies have shown that if a person maintains on her days of the same sleep/wake pattern of her work shift, her adjustment is easier and quicker. Also, for staff development classes, the teacher can be aware of times best suited for retaining Information, depending on the shift her students work. The administrative nurse can be aware of the effects that lack of sleep may have on performance and mood of her employees, taking these into account when hiring for a part-time night-shift position, or when counseling prospective or current employees.

LLU Discipline





Graduate School

First Advisor

Evelyn L. Elwell

Second Advisor

Annette M. Ross

Third Advisor

Grenith J. Zimmerman

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Nursing Staff, Hospital; Job Satisfaction; Circadian Rhythm; Sleep Deprivation



Page Count

ix; 114

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives