{
  "id": 51478,
  "title": "Toward scalable ambulatory light dosimetry: sensor-placement bias under naturalistic conditions",
  "url": "https://urgent.news/2026/08/01/toward-scalable-ambulatory-light-dosimetry-sensor-placement-bias",
  "topic": "culture",
  "section": "Culture",
  "published": "2026-08-01T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.07.28.741277v1?rss=1"
  },
  "original_language": "en",
  "account": "Personal light dosimeters are useful tools for assessing exposure under free-living conditions, but sensors are typically positioned away from the eyes, where visual and non-visual responses are most relevant. Chest and wrist placements may enhance adherence and scalability, yet the impact of these placements on error and derived outcomes has not been thoroughly explored. This study quantifies how chest and wrist placement influences time-resolved estimates of eye-level light exposure across various naturalistic settings and derived exposure metrics.\n\nThe researchers compared melanopic equivalent daylight illuminance measurements taken at the glasses, chest, and wrist using identical dosimeter models across eight sites in seven countries. They analyzed these measurements at two levels - time-resolved and aggregated - and used statistical models to estimate placement error and compare daily metrics. They also used hierarchical bootstrap resampling to assess the precision of population-average metric bias across different participant numbers and monitoring durations.\n\nThe findings reveal that body-worn dosimeters generally underestimate eye-level exposure. At the chest, estimated mean errors ranged between -23.1% and -4.2%, while at the wrist, they ranged from -54.7% to -30.3%, with larger errors typically observed at night. Among the 54 daily metrics derived from chest and wrist placements, 19 differed significantly from those measured on glasses. These differences ranged from a median absolute bias of 5% at both placements to maxima of 50% and 84% for chest and wrist, respectively.\n\nThe timing outcomes were comparatively less sensitive to placement bias, but level and temporal-dynamics outcomes were more affected. When monitoring lasted for seven days per participant, the class-median bias standard deviation reached the 5% precision tolerance with 2-16 participants for all classes except temporal dynamics, which required 33 participants at the chest and 59 at the wrist. The study concludes that the validity of dosimeter placement depends on the analytical scale and exposure construct. Chest placement may be beneficial for scalable studies focusing on aggregated timing or duration outcomes, while wrist placement introduces greater and less predictable bias. Near-eye measurement remains the gold standard for small-sample studies, time-resolved exposure level, and temporal-dynamics analyses.",
  "summary": "Background: Personal light dosimeters enable exposure assessment under free-living conditions, but sensors are rarely positioned near the eyes-the relevant site for visual and non-visual responses. Chest and wrist placement may improve adherence and scalability, yet placement-dependent error and its consequences for derived outcomes remain insufficiently characterised. Objective: To quantify how…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}