Let us drive light out!

Pollution in all its multifarious dimensions has become an integral part of modern life. Reams of literature has been rolled out on air (particulate matter), sound and water pollution, and the dangers fraught thereof, leading to a basic level of awareness of the matters. However, neither public nor medical fraternity’s sensitisation is yet discernible to ambient lighting in hospital settings, especially at night time, as another facet of pollution affecting the ‘cognitive, physical, metabolic, and immunological capabilities’ of not only patients, but also of the healthcare workers [1].

Intensive care units (ICUs) are a mandatory sojourn for most of our patients in cardiovascular and thoracic surgery during their hospital journey. These critically ill patients are often dependent on organ replacement and reinforcement therapies and their endogenous circadian rhythms are ‘inherently misaligned and disrupted’. To be sure, there are ‘cell-type specific molecular clocks’ which interact 2-way with ‘severity of organ dysfunction[s] such as severity of brain dysfunction, pneumonia-or ventilator- associated lung inflammation, cardiovascular instability, liver and kidney failure, trauma, and septic shock’ [2] (Fig. 1). These endogenous rhythms are further disrupted by the imperative of 24 × 7 need for care in these critically ill patients and the complex interplay of external factors like artificial lighting, temperature and noise of ICUs [1]. These cues, acting synergistically, can set off a vicious cycle of not only interfering with the restful sleep cycles, but even affecting hard outcomes, including contributing to ICU psychosis and delirium [3]. Unfortunately, nearly 20–50% of ICU patients, and up to 80% of those on mechanical ventilation, develop delirium [4]. This often prolongs ICU and hospital stay [5], increases post discharge 30-day mortality (hazard ratio, HR 1.44; 95% confidence interval, CI 1.08–1.92), besides emergency department visits and hospital readmissions [6]. Even long-term survival is significantly impacted, at least up to 4 years (odds ratio (OR) 1.41, 95% CI 1.26–1.86; p < 0.001), and more so in those > 65 years of age (absolute risk decrease 11.1%; p < 0.0001) [5].

Fig. 1.

Summary on the current understanding of factors of chrono disruption in the intensive care unit (ICU) (left panel). Methods for combined interpretation of different circadian readouts (middle panel) are still unclear. A better understanding may improve outcome prediction and planning of therapeutic interventions for common ICU pathologies (right panel). ARDS, acute respiratory distress syndrome; VILI, ventilator-induced lung injury’ [2]. Reproduced under Creative Commons License

Currently most hospital lighting systems are based on overhead fluorescent luminaires, inbuilt into false ceiling grids. These fixed artificial lights, with no diurnal variations, affect the sleep quality and physiological parameters of individuals [7]. Dynamic lighting systems, with not only illuminance (Lux), but also colour temperature (Kelvin) in synchrony with natural light patterns—white light in daytime, but mellow warm-yellow light late in the evenings and at night—may go a long way in healing, and hastening patient recovery. Heartening are the findings of a prospective observational cohort pilot study, wherein only 46% of patients in the modified rooms with dynamic lighting developed delirium compared to 76% of patients in the standard rooms (p 0.017). Even severity of delirium was 2.3-fold higher in patients in standard rooms (odds ratio 2.292; 95% CI, 1.582–3.321; p < 0.0001) [8]. Besides improved patient outcomes and reduced ICU stays—and thereby costs—dynamic lighting has the potential to contribute to staff welfare in form of mood elevation, reduced fatigue and better sleep quality [9]. Due diligence therefore needs to be exhibited in designing and conducting affairs in hospital settings, more specifically in ICUs, with a view to optimising ‘spectral irradiance of lighting at the patient’s eye level’ [8], as per the time of the day. Jonescu et al. recommend daytime light intensity levels of 1000 to 2000 lx in ICUs, but a significantly lower levels of 30 lx at night to complement the human circadian rhythm [1].

Besides light intensity, even its colour, a surrogate of wavelength matters. Light-emitting diode (LED) lights are generally preferred over incandescent bulbs due to the advantages of increased efficiency, and thereby energy savings, lack of mercury and reduced heat output. However, the LEDs emit light of a shorter wavelength band called the ‘Blue spectrum’, while the light coming from the incandescent bulbs is in the long wavelength light band called the ‘Red Spectrum’ [10]. These bandwidths can be sensed by various sense organs including skin and retina, and have their cascading effects on the endocrine and the autonomic nervous systems of the body. They also affect the internal clock of the body and the circadian rhythm of sleep by modulating melatonin levels [8]. The production of melatonin by the pineal gland gets suppressed by the white light (‘Blue Spectrum’). This disturbs the initiation of sleep, leading to not only reduced sleeping hours, but also to fragmentation of sleep and poor quality of both rapid eye movement (REM) and non-REM sleep, more so the memory-linked REM sleep. Fragmented, shortened and poor-quality sleep has health consequences, especially for staff working long time in ICU settings. It predisposes to risks of obesity, hypertension, diabetes mellitus and cardio- and cerebro-vascular disorders. Sleep perturbations may also lead to emotional lability, depression and mood swings. In some studies, long-term poor quality of sleep has even been associated with malignancies—especially colo-rectal, breast and genito-urinary [11]—and to myocardial infarction and severity of coronary artery disease [12]. These effects are obviously over and above the other, not so trivial, harms in form of eye strain, fatigue, headache and general feeling of lack of energy and lethargy, indirectly affecting their throughput and relationships and attitudes towards patients and colleagues.

Sunlight reigns supreme

Leave alone science, even intuition dictates that nothing artificial comes close to nature, and matters are no different for natural light. It is therefore mundane that greenfield projects should prioritise rooms with windows with the aim of bringing natural sunlight in, rather than creating solid brick works and then trying to embellish them with artificial lights. Strategically placed windows not only break the monotony, but also provide at least views, if not access (if provided—still better), to outdoors. EM Forster’s novel of 1908—and a later (1985) adaptation as a British romance-film—‘A room with a view’ may be set in Edwardian England, but now resonates with emerging science of the twenty-first century. A study of over 6000 ICU patients found numerically shorter ICU stays and reduced costs for those treated in rooms with windows or natural views [13]. Yet another study registered numerically lower pain levels and shorter lengths of stay, albeit statistically non-significant, for those patients serviced in rooms with windows and natural light. Additional benefits included reduction in staff absenteeism (mean 38 to 23 h; p 0.05) and reduction in vacancy rates by 25% (10.12 to 7.49% staff openings per year; p 0.04) [14]. Add to this the collateral benefits of energy savings, cascading to reduced costs and more importantly carbon footprints for a sustainable environment, and we have a win–win situation for one and all.

Just in passing, as it is yet another subject for focused discussion, even outdoor lighting merit attention as it too has consequences for health. In a recent study from Hangzhou, China, Wu et al. found that besides the harmful effects of particulate matter of ≤ 2.5 µm and ≤ 10 µm sizes, as also of NO₂ (Nitrogen dioxide), the hazard ratio for cerebrovascular disease was 1.17 for outdoor night-light, which was highly significant. Though outdoor night-light and air pollution had a standalone independent positive correlation with cerebrovascular disease, however, there was no direct interaction between the two [15]. Lest I dart askew, more on it for another time, and I shall return to matters at hand—indoor lighting.

Understanding the complex interplay of ‘circadian effectors and tissue-specific molecular clocks’ [2], especially in the hospital and ICU settings, is fundamental to personalised care. ‘The nature of the emitted light may enhance the space rather than simply illuminate, thus further adding to a feeling of wellbeing’ [9]. This would lead to not only salutary patient experiences, but in fact improved outcomes. Light, and even sound, pollution thus needs a more focused and cerebrate consideration, and they should not be treated as fringe elements in medicine. Some norms and mandates for physical infrastructure and lighting for hospitals are called for and should be imposed with same acuity as being practiced for other facets of delivery of healthcare, like prenatal sex determination. Governments and regulatory bodies, such as National Accreditation Board for Hospitals (NABH), must include them in their charter of mandatory compliances for physical infrastructure of healthcare institutions. The consequences of overlooking them are in the realm of serious, even existential, import for the patients and the healthcare workers alike. Ignore, if we do, it shall be to our, and our patients, peril.

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