Light and Noise: Objectively Assessing Environmental Risk Factors for Delirium in the ICU

Delirium - derived from the word lira, Latin for furrow - literally means "to get off track". Historically, signs and symptoms of delirium have been taunted as "insanity". Recognition of delirium as a medical entity with relevance to both morbidity and mortality, especially in in critically ill patients, is a relatively recent development. However, research into delirium, its prevention and treatment, is now in focus of scientific efforts by epidemiologic researchers and international societies alike.

Delirium now is a medical condition both recognised in current versions of the International Classification of Diseases (ICD-10) and the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). It is characterised by some disturbance in attention and awareness, acute onset and at least one additional disturbance in memory, orientation, language, visuospatial ability or perception, which cannot better be explained by another neurocognitive disorder and when there is evidence that the disturbances are a \"direct physiological consequence\" of another medical condition, substance intoxication or withdrawal, toxin, or various combinations of causes.

While historically sometimes regarded as an inalterable consequence of disease, delirium has been recognised as a significant contributor to both morbidity and even mortality in hospitalised patients, especially in critically ill individuals who require intensive care. Several risk factors for the development of delirium in intensive care units have been identified previously. However, many of these are factors not modifiable by caregivers (e.g., advanced age, frailty, pre-existing cognitive impairment, smoking, alcohol consumption, previous isolation, etc.) While some aspects of environment and interventions (especially endotracheal intubation, use of physical restraints and sedation with benzodiazepines, postoperative pain) have been found to be strongly associated with the development of delirium, assessment of the ICU environment itself as a potential modifiable risk factor is insufficient to this date.

Intensive care is known to be associated with high noise levels; attempts to reduce this noise pollution or provide protection from it may be worthwhile interventions to reduce delirium incidence. However, despite first attempts to establish associations between noise levels and delirium occurrence, no target values for possible future interventions have been established yet.

This study seeks to evaluate, whether potentially modifiable environmental factors in intensive care units, such as disturbances by noise or dazzling by light are associated with the development of delirium in critically ill patients. Knowledge derived from this investigation could change both the process of care provision in intensive care units as well as the design of ICUs in general in the future. Such changes could potentially improve outcomes, which would be much desired progress in delirium care, where both non-pharmacologic and pharmacologic therapeutic approaches have not convincingly been shown to be of benefit.