Light has a profound impact on humans, and ongoing clinical research is being carried out on the biological and physiological effects of light on sleep, health and wellbeing. Wearable light loggers are lightweight wireless devices that measure the light doses that humans incur over time. though new standardised methods and metrics have been introduced in CIE S026, calibration and characterisation of such dosimeters remains challenging. This metrological gap extends to UV radiation dosimeters. This project will provide guidance on the characterisation and use of wearable light loggers and the data they produce to ensure their reliability for the studies that use them.
Daylight has always been part of human life, regulating physiological activity and cadencing many aspects of society. At the same time, the invention of electric lighting has led to more and more people spending the day indoors and lately, working from home. However, the intensity of artificial light is a fraction of that of daylight and the spectral composition is also different. While the study of sources and lighting can always be done in laboratories or controlled conditions, the direct effects of light on human physiology needs field measurements of the light dose humans receive in real settings.
Moving laboratory equipment being highly impractical, wearable light loggers have been used to assess the light exposure of humans in clinical research, as they can be carried and provide first-hand data about light exposure throughout the day of a subject. However, their compact and lightweight, black-box design introduces a variety of limitations that leads to inaccuracies, inappropriate metrics or non-representative data. How the data is processed depends on a number of parameters for each device, such as the number and type of sensor used, sampling rate, data format and model. There is no current guideline or standard for the characterisation of these devices, leading to highly unreliable data and wasted time due to inappropriate device specifications and/or data processing and interpretation.
In TN002:2014, CIE has identified the need to harmonize photobiological and photometric quantities. With the rapidly evolving field of lighting (future revision of CIE S025, publication of CIE S026, introduction of daylighting by EN 17037 and revision of workplace lighting in EN12464-1) and the spread of wearable devices of all kinds, it is important to keep metrology recommendations and guidelines up to date to ensure reliable studies that underpin future health recommendations and policies.
