Metrics of circadian lighting for clinical investigations

Abstract

There are currently no accepted metrics for summarising lighting conditions in studies aimed at investigating effects mediated by the circadian system. The objectives of this paper are to propose a set of metrics for capturing circadian variations in environmental lighting conditions and to compare two different lighting regimes applied to patient rooms. Our metric design emphasises the characterisation of light stimuli over time, e.g. their spread over one or more days. Lighting measurements for comparative assessment were taken in 20 beds in the intensive care unit of the Jeroen Bosch Hospital. Lighting conditions between the intensive care unit beds differed significantly across a number of circadian metrics. The proposed set of metrics offers a simple yet comprehensive approach to characterising lighting conditions from the circadian perspective with direct application in clinical studies investigating the effects of light on health.