Abstract
Background Night-shift work disrupts circadian rhythms and exposes nurses to inadequate lighting, negatively affecting cognitive performance and physiological health. Circadian rhythm interventions, particularly those adapted to sex-specific responses, may help mitigate these risks. This study examined the effects of correlated color temperature (CCT), light intensity, and exposure duration on heart rate variability (HRV) and sustained attention in night-shift nurses, emphasizing gender differences. Methods Sixty-four nurses participated under controlled conditions (22–24°C, ergonomic seating). Sessions were randomly scheduled between 11:00 PM and 1:00 AM, coinciding with peak fatigue and melatonin onset. The lighting intervention consisted of eight conditions combining light intensities (500 and 1000 lux), CCT levels (3000 K and 6500 K), and exposure durations (10 and 20 minutes). Illumination was delivered via a localized, adjustable light box. HRV indices and cognitive performance (2-back task, Psychomotor Vigilance Test) were measured before and after exposure. Statistical analyses included paired t-tests, three-way ANOVA, and non-parametric tests, with significance set at p < 0.05. Results Lighting conditions produced distinct autonomic responses by gender. In females, moderate-intensity cool light and high-intensity warm light increased sympathetic activity and reduced parasympathetic activity, while low-intensity warm light improved relaxation and cardiac balance. Male responses were more uniform, with high-intensity cool light enhancing parasympathetic activity. Cognitive performance slightly improved across both sexes, though no significant independent or interactive effects were found. Females showed greater sensitivity to light-related changes in sustained attention. Conclusion Findings highlight the importance of multidimensional, sex-specific lighting interventions to mitigate night-shift-related impairments in occupational settings.