Validating the Use of Wrist-Level Light Monitoring for In-Hospital Circadian Studies

Abstract

This clinical methods comparison study describes the difference between light levels measured at the wrist (Actiwatch-L) and at the eye (Daysimeter) in a postoperative in-patient population. The mean difference between the two devices was less than 10 lux at light levels less than 5000 lux. Agreement between the devices was found to decrease as eye-level light exposure increased. Measurements at eye level of 5000 lux or more corresponded to a difference between the devices of greater than 100 lux. Agreement between the eye- and wrist-level light measurements also appears to be influenced by time of day. During the day, the measurement differences were on average 50 lux higher at eye level, whereas at night they were on average 50 lux lower. Although the wrist-level monitor was found to underestimate light exposure at higher light levels, it was well tolerated by participants in the clinical setting. In contrast, the eye-level monitor was cumbersome and uncomfortable for the patients to wear. This study provides light-exposure data on patients in real conditions in the clinical environment. The results show that wrist-level monitoring provides an adequate estimate of light exposure for in-hospital circadian studies. (Author correspondence: [email protected])

Keywords:

• Daysimeter
• Actiwatch-L
• Environmental monitoring/instrumentation
• Hospital
• Light
• Circadian
• Entrainment

ACKNOWLEDGMENTS

This work was funded by a University of Auckland Staff Research Award to G.R.W. and an equipment grant from the Maurice and Phyllis Paykel Trust. A.C.N.J. received a University of Auckland Doctoral Scholarship. M.J.G. received a University of Auckland summer studentship stipend. We are grateful for the participation of the clinical staff from the Cardiovascular Intensive Care Unit and Cardiovascular Ward 42 at Auckland City Hospital, Auckland District Health Board, New Zealand. We are grateful to Professor Dan Kripke for sharing information regarding his work on this topic.

Declaration of Interest: The authors report no known conflicts of interest. The authors alone are responsible for the content and writing of the paper.