Assessing the health impact of indoor air purification using health data obtained from Apple Watch wearers

Abstract

PM2.5 poses significant health risks. While indoor air purification is a proven mitigation approach, most studies have used medical devices with limited usability and practicality. Thus, we used Apple Watch health metrics to assess short-term physiological responses in a randomized, double-blind, crossover real-world indoor purification intervention – first of its kind in the UAE. 41 healthy, non-smoking young adults underwent two 2-week interventions (real and sham filters), separated by a 1-week washout. Collected Apple Watch metrics include: heart rate (HR), heart rate variability (HRV), (daily) resting heart rate (RHR), sleep respiratory rate (RR), and blood oxygen saturation (SpO₂). Daily timelocation surveys enabled personal PM2.5 exposure estimation. Real purification reduced home PM2.5 exposure from 8.1 μg/m3 to 1.7 μg/m3, associated with significant changes in HR (–0.68%), sleep RR (–0.25%), and SpO₂ (+0.10%). When accounting for exposure across all locations, an IQR reduction in PM2.5 exposure was significantly associated with changes in HR (–1.02%), RHR (–1.07%), sleep RR (–0.39%), and HRV (+1.86%). SpO₂ showed a near-significant increase (+0.04%, p = 0.110). Our findings supported the use of indoor air purification to reduce PM2.5 exposure, linked to health metrics improvements, and the feasibility of using the Apple Watch in environmental interventions.