Study reveals how light affects the well-being of patients in hospitals

lighting hospitalsA group of researchers at the Cleveland Clinic in the USA the has shown that there is a correlation between levels of exposure to light during the day and the psychological state, level of fatigue, and even pain of patients. The study suggests that patients in a normal hospital room, are sometimes exposed to too little light during the day and can not find a normal sleep-wake cycle. Other studies show that winter depression (SAD) is related in some countries to the lack of daylight during certain months of the year, during the fall or winter.

 Impact of lighting in hospitalized patients

To assess whether the light could play a role in healing inpatient, Esther Bernhofer, lead author of the study, and her colleagues collected data from 40 men and women hospitalized between May 2011 and April 2012. Patients wore a wrist device for 72 hours to measure their state (standby or asleep), and the level of exposure to light. These patients completed questionnaires to assess their psychological state, and the level of pain they felt. In general, the patients analyzed slept little, with frequent sleep interruptions, and an average of only four hours of sleep per night. Patients who were less exposed to the light during the day were generally more depressed and more tired than those who were exposed to a higher level of lighting.

 A minimum of 1500 lux during 15 minutes a day

On average, patients in the study were exposed to only 105 lux during the day. As a comparison, the average office lighting provides approximately 500 lux, and a sunny day can provide up to 100,000 lux. Previous studies have shown that a minimum of 1500 lux was necessary to establish a normal sleep-wake cycle, but it was better to be exposed to at least 4000 lux over eight hours, according to professor Bernhofer.

“So far, no one has analyzed the relationship between lighting and states such as sleep, mood and pain in the hospital,” said professor Bernhofer. ”

According to the authors, this study provides a basis to improve lighting in hospitals in order to favor cycles of sleep and wakefulness in patients, improving mood of patients and helping them to reduce pain in hospitalized adults. However, this study is only a preliminary basis, and should not be considered sufficient to change the lighting strategies in hospitals. It provides insight so as to improve the overall patient experience at the hospital, and try to accelerate the healing process.

How to assess the quality of lighting installations in the workplace

Lighting in the workplace is a key environmental factor for employees: we need to set up an appropriate work environment. Different levels of lighting are required for different types of work – close, accurate work such as soldering a control panel will require higher light levels than a waiting room.

Many laws and standards regulate lighting in the workplace. Units of measures are typically used by professionals to assess the quality of  lighting in the workplace.

Here is an overview:

Luminous fluxThis is the amount of energy emitted by a source in the form of visible light in the entire space per unit time.FLumen lm
Light intensityAmount of radiated light emitted in a given point source direction.ICandela(Cd)
LuminanceLuminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. Measures the light intensity collected in a direction and at a point of the light reflected from an illuminated surface. L’appareil de mesure s’appelle un luminancemètre.Lcd / m2(Candela per m2)


IlluminanceIilluminance is the total luminous flux incident on a surface, per unit area.The instrument is called a lux meter. This is an important unit of measur for the standards of comfort and safety.ELux (lx)
Luminous efficiencyThe luminous efficiency of a system depends not only on the source, but also on the accessoriesof the light fixture (reflectors, light distribution grid, transparent protection).Lm / WLumen / Watt
Color temperatureThe color temperature is used to determine the temperature (actual or “virtual”) of a light source, from its color.KKelvin
LifetimeThis feature is important when the cost of replacing the bulbs is expensive (if it is difficult to change the bulbs, for example in the case of high ceilings). Hr



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