Lighting boosts office workers' sleep by 26 minutes
THE INSTALLATION of personalised, controllable lighting in an office has led to workers sleeping longer by an average of 26 minutes.
The improved sleep duration was reported by workers who had, in general, cooler and brighter lighting with a degree of personal control over the the intensity and colour temperature.
The study – by Eindhoven University of Technology – provides for the first time a qualitative measure of the importance of personalisation in improving wellbeing.
The office workers were first exposed to a randomly selected lighting regime for three weeks and then a new test regime for the following weeks. The workers in a control group received standard office lighting of an average illuminance of 500 lux on their desks in a neutral white light while those in the test group got a dynamic light with varying colour temperature and intensity.
This light was customised to the test person’s age and whether he or she is a morning lark or a night owl.
Measuring the light close to the eye, the researchers discovered that the workers with personalisation showed a higher illuminance level in the early morning. The colour temperature level at the desk and close to the eye was also higher in the personalised, dynamic scenario, regardless of the time.
Those employees in the personalised lighting group received better tuned lighting exposure, in spite of the fact that they were mobile and that daylight contributions were allowed in all conditions.
The subjects reported to have slept 26 minutes longer on average in the personalised scenario.
To verify the findings, the researchers will conduct further detailed analysis to control for potential confounding variables such as light sensitivity, general sleep quality and period of assessment as well as for actual light exposure as measured with the light loggers.
This means that the current findings should be considered with caution as they are still inconclusive.
Nevertheless, they say the power of personalisation is an important early finding.
Another striking discovery was the diversity of opinions on light intensity and colour temperature. The team reports that the findings ‘clearly illustrate the need for personal control’. This is especially important when offering more ‘extreme’ scenarios, such as very bright or very blue light.
‘We learned that even though personal control is exerted only incidentally, users emphasise how much they appreciated being able to tweak the light settings.
User awareness of vitalising effects and health benefits: Only few participants appeared aware of any alertness-, health- or productivity enhancing effects of light in general. If granted control, most participants report tuning conditions to visual comfort, which is of course only one component of light’s effects.
The study is a part of a project called Personalised Intelligent Lighting Control Systems (PILCS) led by Professor Yvonne de Kort. The colour tuning lighting system was supplied by Glamox.