Salivary Biomarker Profiles and Chronic Fatigue among Nurses Working Rotation Shifts: An Exploratory Pilot Study

Abstract

Although nurses' fatigue affects their well-being and patient safety, no effective objective measurements exist. We explored the profiles of salivary biomarkers associated with nurses' chronic fatigue across several shifts. This longitudinal study involved 45 shiftwork nurses and collected their saliva samples before two night and two day shifts for a month. Chronic fatigue was measured using the Cumulative Fatigue Symptom Index before the first night shift. Biomarker profiles were analyzed using hierarchical cluster analysis, and chronic fatigue levels were compared between the profiles. Cortisol profiles were classified into high- and low-level groups across two day shifts; the low-level group presented significantly higher irritability and unwillingness to work. Secretory immunoglobulin A (s-IgA) profiles across the four shifts were classified into high- and low-level groups; the high-level group had significantly higher depressive feelings, decreased vitality, irritability, and unwillingness to work. Cortisol (two day shifts) and s-IgA (four shifts) profiles were combined, and (i) cortisol low-level and s-IgA high-level and (ii) cortisol high-level and s-IgA low-level groups were identified. The former group had significantly higher chronic fatigue sign and irritability than the latter group. The profiles of salivary cortisol and s-IgA across several shifts were associated with nurses' chronic fatigue.

Keywords: biomarkers; fatigue; nurses; saliva; shift work schedule.

Figure 1

Illustration of the study procedure. Abbreviations: CFSI, Cumulative Fatigue Symptom Index. Note: The arrows indicate the shifts investigated. The intervals between each shift (average number of days) are indicated between arrows. The circles indicate each measurement point.

Figure 2

Profiles of the salivary cortisol, secretory immunoglobulin A (s-IgA), and oxytocin. Abbreviations: Day, day shift; Night, night shift; s-IgA, secretory immunoglobulin A. Note: Data are shown as the mean (error bar, standard error of measurement) of each biomarker concentration. (A): Dynamics of the salivary cortisol concentration (μg/dL) between day shifts in the high-level (n = 24) and low-level groups (n = 19). (B): Dynamics of the s-IgA concentration (ng/mL) between the four shifts in the high- (n = 21) and low-level groups (n = 19). (C): Dynamics of the salivary oxytocin concentration (pg/mL) between the four shifts in the high- (n = 13) and low-level groups (n = 16).

Figure 3

(A) Dynamics of cortisol levels across two day shifts (solid line) and secretory immunoglobulin A levels (dashed line) across four shifts of profiles of both combined biomarkers with means and standard errors. (B) Comparison of the median complaint rate (%) of the Cumulative Fatigue Symptom Index between profiles. Abbreviations: s-IgA = secretory immunoglobulin A. Note: * p < 0.050, ** p < 0.010.