Ergonomic lighting considerations for the home office workplace

2.1 Blue light from ubiquitous electronic screens

Electronic screens have become an integral technology for almost all aspects of our everyday life, including our homes. Computer monitors, laptops, tablets, cellphones, TV screens, and even a handful of futuristic refrigerators have expanded our time spent on screens in a given day [6]. Typical screens produce light via backlit Light-Emitting Diodes (LEDs), which may display a spectrum of colors, but with peak emittances in blue wavelengths [7, 8]. While there are some exceptions to screen lighting (e.g. “night time mode” that shift screen tones to more red and orange hues), people are generally exposed to a large amount of blue lighting at most times of day, and this exposure is greater for those using electronic displays every day [9]. This is important because of the role blue light plays in regulating our circadian rhythm and maintaining our health and wellbeing.

Blue light is a short-wavelength light between 400 and 490 nm, and it suppresses melatonin production in humans [8, 10]. Blue light passes through the cornea and the lens of the human eye, and hits the retina, which is responsible for photoreception [8]. Specifically, within the retina, blue light activates the intrinsic photosensitive retinal ganglion cells (ipRGCs), which are believed to be the photoreceptors that help regulate the body’s internal clock, and therefore blue light exposure influences our circadian system function [11, 12]. Thus, blue light from daylight, from indoor lighting sources and from electronic screen exposure impacts how we perceive and perform within our surroundings because of its direct and indirect impact on our daily rhythms and wellbeing.

2.2 Screen light impact on ocular health

Blue-enriched screen light can directly negatively impact human ocular health. Compared to longer wavelength light, blue light exposure for minutes to hours can inflict much more damage to various cells in the eye [13]. Blue light has been shown to increase ocular damage in the form of dry eye, cataracts, and age-related macular degeneration [8, 14].

Dry Eye Syndrome (DES) is one of the world’s leading eye conditions [15]. Researchers exploring the role of blue light in patients with DES found that wearing protective lenses that reduce ocular penetration of short-wavelength blue light improves visual function for research participants with DES [16]. DES is also a principal ocular cause for Computer Vision Syndrome (CVS), in which blue screen lighting may be a key contributing factor [17, 18]. CVS is a collection of ocular problems associated with computer use and impacts approximately 70% of the computer-using population [19, 20]. Typical symptoms reported by 90% of computer users experiencing CVS include eyestrain, headaches, ocular discomfort, dry eye, diplopia, and near- and far-sighted blurred vision, which have shown to negatively impact work productivity [18]. DES and CVS are two relatively low-risk but extremely prevalent eye syndromes that may be correlated with blue light exposure from electric screens.

Higher-risk eye conditions leading to blindness or increasing loss of vision may also be correlated with blue light exposure. Cataract development is the leading global contributor to blindness, in some places accounting for up to 44% of visual impairment [20]. While some research suggests smoking and diet are key non-genetic contributing factors to cataracts, light exposure is still an undeniable source of risk [21, 22]. However, not all light is equally as damaging. Kuse and colleagues conducted research exploring the impacts of different colored LED light on Murine cone photoreceptor-derived cells (661 W) and found that ocular damage is wavelength dependent; short wavelength LED light (i.e. light in the blue range) has more toxic effects compared to white and green light [23]. Wegner and Khoramnia propose that cataract development is the body’s self-defense reaction to protect the retina from oxidative damage [24]. Zhao et al. say that blue light’s easy access to the retina results in oxidative stress on the outer segments of the photoreceptors, which contribute to age-related macular degeneration [14, 25]. In other words, it’s hypothesized that one reason some people may go blind is because blue light has caused severe retinal injury and the eye is trying to prevent further damage. This information indicates that blue light exposure can be partially responsible for high-risk eye conditions, such as cataract and age-related macular degeneration, due to its impacts on the retina.

In summation, screen light has a negative impact on ocular health. Blue light’s impact on the retina contributes to the most prevalent eye health issues in humans [8, 23–25]. Because increased screen exposure increases human exposure to blue light, the risk of ocular disease becomes more prevalent [8, 14].

2.3 Screen light impact on circadian rhythm

Blue-enriched light exposure does not only impact ocular health but can also have large-scale impacts on human wellbeing [26, 27]. Because of its role in circadian rhythm and hormone production, the effects of blue light from screens can be far reaching [27–32].

A common piece of advice in today’s digital age is to avoid technology in the bedroom, and to avoid screens 1–2 hours before bed [26]. While tedious in practice, evidence shows screens have a large negative impact on sleep quality and quantity due to melatonin suppression. Figueiro and fellow re-searchers conducted a study to understand just how much electronic screens suppress melatonin by asking participants to engage in computer tasks at night with different colored goggles, finding that participants wearing goggles colored to reduce blue light waves showed statistically lower melatonin levels [27]. Exposure to blue light through electronic screens results in reduced melatonin production, which also results in negative impacts on sleep. Green and colleagues conducted research finding screens emitting short wavelengths (i.e. blue light) resulted in an increase in time it took for participants to fall asleep, shorter time spent asleep, increased number of times participants woke up at night, and increased amount of time participants spent awake when they woke up at night, compared to those exposed to long wavelength light [28]. Artificial light at night negatively impacts quantity and quality of sleep because of exposure to blue light, and research suggests this may have quick effects [27, 28]. In response to this concern, software applications have been developed that reduce the amount of blue light emitted from a screen. Testing of one such application (Night Shift, Apple Inc.) showed that while this does change the color temperature of the screen it does not significantly cha-nge the suppression of melatonin that occurs with the use of self-luminous displays prior to bedtime [29].

Blue light from screens not only impacts sleep, but also results in carry-over daytime impacts due to circadian rhythm shifts [30, 31]. A six-night study interested in understanding the impact of blue light exposure time on sleep found that even one night of screen light exposure (for a duration of 2 hours in the evening before bed) led to dampened nocturnal melatonin production, altering participants circadian rhythm, and resulting in increased daytime sleepiness, negative emotions, and difficulties paying attention the following day [30]. Similarly, researchers in Japan studied how blue light exposure at night impacted participants the following morning and found 2 hours exposure to blue light in the evening did not impact sleep architecture but resulted in increased drowsiness and suppressed energy metabolism the following morning [31]. Blue light from electronic screens can have “hangover”-like effects on individuals who use them at night, resulting in negative repercussions the following day.

However, blue light exposure from screens doesn’t only need to have undesirable impacts. Because of blue light’s impact on melatonin suppression, exposure in the morning may counteract negative effects from the night before [32]. Münch and colleagues explored the relationship between morning and evening lighting conditions, finding that blue light in the morning resulted in quicker reaction times, indicating that blue light in the morning could re-set circadian rhythm [32]. Blue light is a powerful dictator in human awake-sleep cycles and has shown to reset internal clocks regardless of time of day. Vetter et al. conducted an experiment on 66 employees in Germany by changing office lighting and asking participants to keep sleeping logs. Over the course of five weeks, the researchers found that individuals exposed to white lighting maintained sleep cycles that paralleled daylight, while those exposed to blue-enriched white lighting maintained sleep cycles dictated by work hours [11]. Although research studying the effects of screen time in the morning is sparse, several studies support the claim that blue light exposure subdues melatonin production, and therefore morning exposure will result in greater feelings of wakefulness [11, 32].

Together this suggests that blue light has a powerful influence on human circadian rhythm that can be negative if used at irresponsible times [11, 27–31]. Because electronic screens are frequently partnered with blue light exposure, it is crucial to use these tools during times of wakefulness and avoid them before bed.

2.4 Self-illuminating screens impact during COVID-19

COVID-19 and its corresponding restrictions have created human behaviors that may be counter-intuitive to responsible blue light exposure. Through a series of effects, research suggests that increased screen time due to COVID-19, in tandem with the effects of blue lighting from screens on circadian rhythm, is negatively impacting human wellbeing [33–40].

Safety orders have led to working/schooling from home, physical isolation, and decreased time committed to commutes, resulting globally in an increase in screen time [9]. Within the United States alone, its estimated that individuals increased their average screen time to 13 hours a day since COVID-19 sent everyone home [33]. ‘Stay at Home’ orders have not only increased screen time, but also resulting in a decrease in time spent outside. A study conducting cross-sectional data analysis on a larger study concerning COVID-19 and wellbeing, showed that participants spent significantly less time outside after restrictions were instated during the COVID-19 pandemic compared to pre-restriction behavior [34]. This reduced time outside puts humans more at risk to circadian rhythm shift due to artificial light, such as screens, because of a lack of natural light. Researchers in Colorado studied the effects electric light has on circadian clocks over the course of two weeks with eight participants via a camping trip with only exposure to natural light and were able to conclude that artificial lighting and prolonged time indoors delays circadian clocks due to decreased sun exposure during the day [35]. In other words, the environment that most office-employed individuals have spent a majority of their time in during the COVID-19 pandemic fosters an atypical circadian rhythm, or a rhythm not synchronous with local day/night cycles.

These circadian rhythm disruptions can severely impact wellbeing because of its large role in body regulation, which can easily result in disrupted sleep cycles, erratic mood, and decreased productivity [36]. A meta-analysis of circadian disruption and physical health conducted in 2012 shows a positive relationship between atypical circadian rhythm and metabolism and obesity, susceptibility to illness, cancer, and heart disease [37]. A meta-analysis of rhythm disruption and mental health conducted in 2020 shows positive relationships between irregular circadian rhythms and depression, anxiety, bipolar disorder, and schizophrenia [38]. In addition to chronic stress, anxiety, and depression risks humans face from social factors (job security, social isolation, etc.) of the COVID-19 pandemic, increased mental health risks are present due to environmental factors, like lighting, impacting circadian rhythm disruptions [39].

Unfortunately, research suggests a parallel relationship between depression and screen time in adults and adolescence [37, 38], and screen time and anxiety in adolescence [39,40, 39,40]. Because of these relationships between mental health and screen usage, screen-use behaviors evident during the COVID-19 pandemic threaten a dangerous health pattern. Shelter In Place orders have facilitated an increase in screen time, which has aided in disrupting circadian rhythms, negatively impacting mental health, providing the potential to result in more screen time, continuing the cycle. This cyclical downward trend isn’t sustainable, but current COVID conditions support its development. In this challenging time, humans are placed in a position to fight their biological clocks by spending increasing amounts of time on electronic screens. It is crucial to take careful steps forward that aid in maintaining a traditional circadian rhythm (following day/night patterns), by limiting time and duration of exposure to blue light from screens.

3.1 Daylight’s impact on human health and wellbeing

While blue light is a strong determinant in circadian rhythm, natural daylight also plays a substantial role. Daylight is a zeitgeber for our circadian rhythms, helping maintain our diurnal pattern following day/night sun exposure [43]. The impact of daylight exposure on circadian rhythm results in body temperature regulation, hormone production, sleep, activity-rest behavior, alertness, mood, and performance throughout the day [44]. When an individual’s circadian rhythm is misaligned with sunlight and they are thrown off their traditional 24-hour pattern, they can experience sleep disorders, distorted feeding behaviors linked to altered hormone production and metabolism rates, psychiatric disorders, premature death, cancer, cardiovascular dysfunction, immune dysregulation, reproductive problems, and learning deficits [45, 46]. For example, Scheer and colleagues conducted a study altering ten healthy adult participants’ circadian rhythms to operate on a 28-hour rather than 24-hour day. Their results revealed that after only ten days the circadian misalignment significantly altered individuals’ metabolic function resulting in glucose responses in a pre-diabetic range [47]. Research suggests that circadian rhythm maintenance results in positives, but also negatives in cases of shift or disruption. Regular and consistent exposure to daylight is key in sustaining circadian rhythm hygiene.

However, sun exposure benefits are not limited to circadian rhythm impact. A literature review on the development of myopia in children found through epidemiological research that time outside in the sun results in fewer instances of myopia in adolescents [48]. Additionally, a literature review on the benefits of daylight through windows concluded that, compared to artificial light, sunlight allows for advanced color rendering due to its wider spectrum and large amount of light [43]. Daylight also has impacts on mental health, as supported by research exhibiting a positive correlation between sun exposure and Seasonal Affective Disorder, as well as its effects on depression and bipolar disorder [49–54]. On a biological level, sunlight stimulates vitamin D production, which strengthens immune response and mental health while stabilizing inflammatory responses and calcium homeostasis [55–61]. Research within the elderly population living in Swedish nursing homes found that older people who spent at least 20 minutes outside between 11 a.m. and 3 p.m. experienced significant increases in vitamin D levels and self-reported mental health. This natural exposure led to levels of vitamin D that were comparable or better than oral vitamin D supplements [62]. Daylight has far-reaching positive impacts on human health and wellbeing, and the benefits of its exposure cannot be discounted.

3.2 Daylight in an office environment

Even as evidence supporting the need for daylight continues to grow, humans may still be limiting their access, due in part to their work environment. On average, individuals spend roughly a quarter of their week in their workspace (using a 5-day, 40-hour work week baseline). Depending on the time of year and location, individuals can expect to lose a minimum of 30% (in an area with 24-hour daylight), up to 100% (in an area with less than 8-hour daylight), of their daylight to the time spent at work. It is important to maximize daylight exposure in the workplace because of the amount of time individuals spend at work and the critical role that sunlight plays in human health. In an area within Mediterranean Southern Europe, scientists studied 100 white- and blue-collar workers of a wine producing company and discovered a significant direct impact between daylight exposure and levels of job satisfaction, general wellbeing, and intention to quit [63]. The relationship between daylight exposure and work performance may be directional rather than correlative, as a meta-analysis revealed that companies who move to office buildings with more daylight experience a 5–25% increase in productivity [61]. Research studying the impact that daylight has on office windows showed a link between windows and effects within and outside of the work environment. In fact, Boubekri et al. conducted a study on the effects that window access to office employees had on wellbeing, sleep quality, and activity, and found that those with access to windows engaged in more physical activity, slept an average of 46 minutes longer, had more access to natural light, and scored higher on the Short Form 36, indicating better mental health compared to those without window access [52]. In an office environment, most daylight exposure can be assumed to be received through windows because of traditional architectural elements of office buildings. This can generate debate about whether benefits from windows come from exposure to sunlight or exterior views because humans intuitively favor exposure to natural elements [64]. However, An et al. discredited this myth by isolating exposure to natural elements and sunlight while studying their effects on employees. A total of 444 participants completed an online survey in which researchers found evidence that sunlight had a more powerful positive effect on depressed mood, anxiety, job satisfaction, organizational commitment, and occupational stressors than natural elements [61]. Specifically, within the office environment, daylight has shown to positively impact employee health and wellbeing. This environment is especially important to concentrate on because it is where humans spend the majority of daylight hours.

Unfortunately, though research suggests exposure to light and windows results in positive health effects and increased productivity for employees, its distribution is not equitable. A study analyzing the cost of office space and access to daylight in 5,154 Manhattan workplaces found that, even when controlling for variables such as neighborhood and contract characteristics, offices with high levels of daylight result in a 5–6% rent premium compared to office spaces with low levels of daylight [65]. Access to daylight comes with a price tag that creates a disparity between exposure levels based on wealth, or how much a company is willing to pay for their employee work environments. In areas with significant wealth gaps or high demand, especially dense major cities, sun exposure is even more difficult to come by; 74% of office space in Manhattan has low levels of daylight and offices in major Swedish cities have an average 0.5% daylight factor instead of the recommended 1% [65,66, 65,66]. Overall, access to natural light is lacking within workplaces across the globe, despite evidence of holistic benefits.

3.3 Daylight and COVID-19

One unexpected benefit of the COVID-19 pandemic is the increase in remote home office work. Office employees across the globe were sent home in an effort to mitigate the spread of the disease, offering the opportunity for an alternative working environment. The availability of daylight access may increase due to individuals’ autonomy to pick their own workspaces within their homes, but it is also likely more variable across an employee base compared to sunlight exposure in office locations (especially when considering housing inequity). Just as Turan and colleagues identified a 5–6% rent premium on office space dependent on daylight, a similar trend is likely to exist in residential buildings as well [65]. In a dense city landscape where maximum sunlight exposure is only available on top levels of a building, access to sunlight may be attainable for only a select few. Researchers Danton and Himbert analyzed vertical rent curves in residential buildings within the five largest cities in Switzerland and uncovered a positive correlation between floor level and rent price, primarily due to amenities like views out of windows [67]. While working from home, access to daylight is reliant on home value (depending on geographic location), but benefits exist for those who have it.

There does, however, exist a gap in the research regarding sunlight exposure for teleworkers, but data on sunlight exposure levels (and its associated benefits) within residential buildings is available. Researchers in Glasgow, Scotland created a sunlight exposure model and interviewed individuals within apartment towers on psychological and physical health and health behavior, while measuring and controlling for other ambient factors, and found that those who have less sunlight in their homes are less psychologically healthy than those with more sunlight [68]. Depending on sunlight availability within a home, participants may now have access to 100% of daily sunlight by relocating their workstation near a window, an option that is customarily not available in a traditional office space.

Increased access to windows within the home may serve as a benefit for employee health and organizational productivity, but it can also result in greater discomfort. Too much sunlight can result in unease from glare, visual discomfort, difficulty with thermoregulation, lack of privacy through windows, excessive light exposure, or distraction [43]. However, because of humans’ affinity towards daylight, research has suggested that tolerance for these discomforts is increased for sunlight compared to artificial light. Glare can be a negative effect, but humans have shown to tolerate it from daylight through windows based on the level of interest, attractiveness, and subject of the views outside the window [69–73]. Researchers Chinazzo, Wienold, and Andersen experimented with thermal conditions and sun exposure and found that warmer conditions are better tolerated by individuals who have daylight in the room compared to the same level of warmth in an artificially lit space [74]. While increased sunlight exposure may provide increased opportunities for discomfort, human preference for daylight buffers the tolerance of these factors. Still, it is important for ocular health and safety to avoid glare and reduce strain. To do so, ergonomists recommend positioning screens and monitors perpendicular to windows, as it reduces the potential for glare [75].