Background: Night shift duties are crucial in the ICU to ensure care continuity, where critically ill patients require round-the-clock care. However, cumulative night shift duties may disturb circadian rhythm, insomnia, fatigue, and depression, and require further elucidation.

Objectives: This study aims to examine the negative consequences of various night shift patterns on insomnia, fatigue, and mental health of ICU Workers.

Methods: A cross-sectional study examined how cumulative night shift duty affects insomnia, fatigue, and mental health in critical care providers (CCPs).

Results: A total of 1006 participants completed this study between June 2022 and March 2023, including 54.5 % males. About 35 % were between 20 and 30 years of age, and Respiratory Therapists accounted for approximately 46.5 % of the entire sample. Most of our respondents (476; 47 %) reported working night shifts, with a monthly range of 8-15 nights. The prevalence rates for moderate to severe clinical insomnia, fatigue, and moderate to severe depression were 42 %, 48 %, and 32 %, respectively. CCPs working 8-15 nights had a 2-fold risk of clinical insomnia than those working fewer than eight nights with (AOR) and 95 % (CI) of 2.12 and 1.41-3.20, while those working ≥16 nights per month had a greater incidence of clinical insomnia compared to those working <8 nights per month, AOR (CI): 3.09 (1.90-5.03). Only those working ≥16-night shifts per month had a substantially higher fatigue risk compared to those working < 8-night shifts per month, with an AOR (CI) of 1.92 (1.19-3.08). Working 8-15-night shifts per month increases depression risks by 34 % compared to the <8-night shifts group, AOR (CI): 1.34 (0.87-2.08). Those working ≥16-night shifts per month showed a higher depression risk than those working <8-night shifts, AOR (CI): 2.53 (1.53-4.19).

Conclusion: A cumulative night shift above eight nights per month is linked with an increased risk of insomnia, fatigue, and depression. The risk of these conditions was significantly directly proportional to the number of night shifts performed per month.