Volume 86, December 2025, 152017Author links open overlay panel, , , Highlights•

Female shift-working nurses often face sleep issues and fatigue, harming their health and job performance.

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Four weeks of daily light device use reduced daytime sleepiness and improved sleep quality in female shift-working nurses.

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Light intervention is safe, low-risk, cost-effective, and promising for workplace programs supporting shift-working nurses.

AbstractBackground

Sleep disturbances and fatigue are prevalent among female shift-working nurses, adversely affecting their health and job performance.

Objectives

This study aimed to evaluate the effectiveness of light intervention in reducing daytime sleepiness, fatigue, and improving sleep quality among female shift-working nurses.

Methods

A randomized controlled trial was conducted at a medical center in northern Taiwan with 80 female nurses assigned to either an experimental or control group. Baseline assessments included demographics, work characteristics, and measures using the Epworth Sleepiness Scale (ESS), Brief Fatigue Inventory (BFI), and Pittsburgh Sleep Quality Index (PSQI). The experimental group used a wearable light device (Re-Timer®) for 30–40 min daily over four weeks, while the control group continued their usual routines. Follow-up assessments occurred on day 14 (T1) and day 28 (T2).

Results

Results from Generalized Estimating Equations (GEEs) analysis showed significant reductions in sleepiness (ESS) at T2 and improvements in sleep quality (PSQI) at T1 and T2 in the experimental group compared to the control (p < .05). No significant changes were found in fatigue (BFI).

Conclusions

The study supports light intervention as a safe, low-cost, and non-pharmacological approach to reduce daytime sleepiness and enhance sleep in shift-working nurses, suggesting its integration into occupational health programs for healthcare providers.

Section snippetsBackground

Nursing is a female-dominated profession, and the nature of patient care requires continuous 24-hour service. As such, shift work is an almost unavoidable aspect of the work environment for most female nurses (Beebe et al., 2017). However, the physiological and psychological burdens of long-term shift work often lead to various health problems, including sleep disorders and chronic fatigue (Zhang et al., 2023). Shift work is a significant environmental stressor that disrupts the mechanisms

Designs and methods

This study adopted a randomized controlled trial (RCT) design and was conducted at a medical center in northern Taiwan. This study was conducted in accordance with the Consolidated Standards of Reporting Trials (CONSORT) guidelines (Schulz et al., 2010).

Setting and sample

The study was carried out between July 1, 2024, and June 30, 2025. Participants included female registered nurses aged 20–45 years who had at least one year of work experience, were working rotating day and night shifts, reported sleep problems, and gave written informed consent. Exclusion criteria included: postmenopausal status; skin sensitivity, including a history of photosensitivity; history of emotional disorders or depression; chronic or malignant diseases; and diagnosed eye diseases

Randomization and allocation

The principal investigator conducted on-site visits to each nursing unit to recruit participants. Eligible individuals were randomly allocated to either the experimental group or the control group using a random numbers table generated in Microsoft Excel. This method of randomization was employed to ensure an unbiased allocation process and to maintain the internal validity of the study.

Outcome measures and instruments

The study was to determine the effectiveness of light intervention on daytime sleepiness, fatigue, and sleep quality in female shift-working nurses. For collection of the research data, Participant Information Form, Epworth Sleepiness Scale (ESS), Brief Fatigue Inventory (BFI), and Pittsburgh Sleep Quality Index (PSQI) were used.

Intervention/data collection

According to the randomization, the group with the light applied was allocated as the experimental group and the group with usual lifestyle was allocated as the control group. For the experimental group, participants received a wearable light device (Re-Timer®) along with an instruction manual and usage guide. Re-Timer® is a university-developed, commercially available wearable light device, designed based on over 25 years of circadian rhythm research at Flinders University. The device has

Data analysis

Data were analyzed using SPSS Statistics version 26.0. An independent samples t-test and chi-square (χ2) test were employed to examine the homogeneity of demographic and work-related characteristics between the experimental and control groups. The Generalized Estimating Equations (GEEs) was used to assess the effects of the light therapy on daytime sleepiness, fatigue, and sleep quality over time. A significance level of p < .05 was adopted to determine statistical significance.

Ethical considerations

This study was approved by the hospital's Institutional Review Board. Written informed consent was obtained from each participant in accordance with the principles of the Declaration of Helsinki. The primary researcher provided eligible participants with a detailed explanation of the study's purpose, procedures, potential risks, and anticipated benefits. Participants were assured that their personal information would remain anonymous, be used solely for academic purposes, and be securely stored

Baseline demographic and work-related characteristics

A total of 80 female shift-working nurses were recruited and randomly assigned in a 1:1 ratio to the experimental group (n = 40) and control group (n = 40). The participants' mean age was 29.94 (SD = 6.07) years. Independent t-tests and chi-square tests were conducted to assess group differences in demographic and work-related characteristics. Results indicated no statistically significant differences between the two groups, except for exercise habits and perceived health status (Table 1).

Effectiveness of light exposure on daytime sleepiness, fatigue, and sleep qualityDiscussion

Shift work disrupts the circadian rhythms in nurses, often leading to sleep disturbances and fatigue. This not only impacts their physical and mental health but also impairs concentration and increases the risk of patient safety incidents (Bell et al., 2023; Rahmani et al., 2025; Yang et al., 2024). Therefore, timely and appropriate interventions to mitigate such symptoms are of great importance. In this study, a four-week intervention was administered using the Re-Timer® circadian light

Limitations

This study has several limitations. First, the sample was limited to 80 female shift-working nurses from a single medical center in northern Taiwan, which may restrict the external validity and generalizability of the findings. Future studies are recommended to recruit a larger and more diverse sample, including participants from different regions, healthcare levels, and genders, to enhance representativeness and applicability. Second, the intervention period was limited to four weeks, which

Implications and recommendations for practice

These findings support the practical application of wearable light devices in clinical settings, demonstrating their effectiveness in reducing daytime sleepiness and improving sleep quality among female shift-working nurses. The Re-Timer® circadian light device employed in this study emits a stable green wavelength with consistent brightness (500 lx; 500 nm), aligning with the physiological mechanisms governing circadian rhythm regulation. In addition, its lightweight, user-friendly, and

Conclusions

The Re-Timer® wearable light circadian device is a safe, effective, low-side-effect, and highly feasible intervention with strong cost-effectiveness. Light intervention represents a promising non-pharmacological approach to alleviating daytime sleepiness and improving sleep quality among female shift-working nurses. This intervention holds significant implications for enhancing their overall health and work performance. The empirical evidence provided by this study offers valuable references

CRediT authorship contribution statement

Shu-Fen Niu: Writing – review & editing, Resources, Conceptualization. Yu-Ying Lu: Writing – review & editing, Writing – original draft, Validation, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Yu-Chieh Lin: Investigation. Kuei-Fen Liu: Writing – review & editing.

Patient consent statement

Prior to commencement, written informed consent was obtained from all participants.

Ethics approval statement

The study received approval from the Institutional Review Board of ***Hospital (Approval No. 20240303R).

Funding statement

This research was supported by Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan (Grant No. 113D004-2).

Declaration of competing interest

The authors declare no conflicts of interest related to this research.

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