A prospective multicentre observational study to quantify nocturnal light exposure in intensive care

Background Disrupted circadian rhythms can have a major effect on human physiology and healthcare outcomes, with proven increases in ICU morbidity, mortality and length of stay. Methods We performed a multicentre observational study to study the nocturnal lux exposure of patients in 3 intensive care units. Results The median light intensity recorded was 1 lux over the 6-hour recording period; however, this is deceptive as it hides short periods of high lux. When looked at in shorter time segments of 30 minutes, there were significant periods of lux higher than a crude median, especially in higher acuity patients. There was a positive correlation between acuity (as estimated by SOFA score) and maximum lux (R = 0.479, p = .0001), median lux (R = 0.35, p = .006) and cumulative lux (R = 0.55, p = .000001). There was no relationship between neighbouring patient acuity and lux. Conclusions Clinicians should practice vigilance at night to provide optimal environmental conditions for patients to minimise potential harm.