Collecting, detecting and handling non-wear intervals in longitudinal light exposure data

Abstract

In field studies using wearable light loggers, participants often need to remove the devices, resulting in non-wear intervals of varying and unknown duration. Accurate detection of these intervals is an essential step in data pre-processing pipelines. However, the limited reporting on whether and how non-wear information is collected and detected has hindered the development of effective data pre-processing strategies and automated detection algorithms. Here, we deploy a multi-modal approach to collect non-wear time during a longitudinal light exposure campaign and systematically compare non-wear detection strategies. Healthy participants (n=26; mean age 28±5 years, 14F) wore a near-corneal plane light logger for one week and reported non-wear events in three ways: pressing an "event marker" button on the light logger, placing it in a black bag, and using an app-based Wear log. Wear log entries were checked twice a day to ensure high data quality and used as ground truth for non-wear interval detection. Participants showed high adherence to the protocol, with non-wear time constituting 5.4±3.8% (mean±SD) of total participation time. Considering button presses, our results indicated that extending time windows beyond one minute improved their detection at the start and end of non-wear intervals, achieving identification in >85.4% of cases. To detect non-wear intervals based on black bag use, we applied an algorithm detecting clusters of low illuminance to our data and compared its performance to detecting clusters of low activity. Performance was higher for illuminance (F1=0.76) than activity (F1=0.52). Transition states between wear and non-wear emerged as a major source of misclassification, and we suggest that combining illuminance and activity data could enhance detection accuracy. Lastly, we compared light exposure metrics averaged across the week derived from three datasets: the full dataset, a dataset filtered for non-wear based on self-reports, and a dataset filtered for non-wear using the low illuminance clusters detection algorithm. The differences in light exposure metrics across these datasets were minimal. Our results highlight that while non-wear detection may be less critical in high-compliance cohorts, systematically collecting and detecting non-wear intervals is both feasible and important for ensuring robust data pre-processing.