Just-in-Time Adaptive Interventions (JITAI) to Improve Indoor Air Quality in Sleep Environments: A Pilot Study
This conference talk presented a pilot study on Just-in-Time Adaptive Interventions (JITAIs) for improving indoor air quality (IAQ) in sleep environments. JITAIs are context-aware recommendation systems originally developed in mobile health to deliver timely, personalized support for self-management. The talk examined whether the same approach can nudge occupants toward indoor setting adjustments, such as window opening, in the built environment.
The presentation first outlined why bedrooms are a promising setting for this intervention. Bedroom environments are highly personalized and adjustable; window opening is a simple and effective strategy for improving IAQ; and JITAIs targeting window-opening behavior remain understudied. The research aim was to develop a smartwatch-based JITAI system for improving bedroom IAQ during sleep and to evaluate it through a two-month field deployment.
The system was implemented on Apple Watch using Coize, an open-source app for message delivery and feedback collection. A JITAI was triggered when the previous night’s mean bedroom CO₂ exceeded 1,000 ppm or PM2.5 exceeded 35 μg/m³, provided that outdoor PM2.5 was lower than indoor levels. The message recommended airing the room for 20 minutes or using an air purifier that night. Effectiveness was evaluated through a micro-randomized field trial in Singapore (n = 12), with each participant completing 60 valid study days. Evaluation focused on perceived usefulness, user adherence (pre-sleep CO₂ drops of more than 100 ppm in 10 minutes as a proxy for window opening), and overnight bedroom IAQ.
The results showed that around 90% of participants perceived the JITAI as helpful. Indicative window-opening events were about 2.6 times more frequent on days with JITAI than without (15.8% vs. 6.2%), although overall adherence remained low at around 16%. The recommended 20-minute ventilation period did not lead to consistent overnight improvements in IAQ, as participants often closed their windows again afterward to save energy.
The talk concluded with implications for future JITAI design, including more timely messages and feedback mechanisms that help occupants recognize the effects of their actions. Next steps include expanding from this pilot to a full-scale analysis with 50 participants, covering additional intervention types such as lighting, noise, and air-conditioning and fan use, as well as examining adherence across message types, JITAI fatigue, and which occupants are most likely to benefit.
Slide Download: Access the presentation slides here.
Related publication: JITAI to Improve Indoor Air Quality in Sleep Environments