Xiaomi
Xiaomi Smart Band 9 validation studies
2 peer-reviewed studies in the CircaTest corpus that validated this device against polysomnography or another reference standard.
Read CircaTest's Xiaomi Smart Band 9 review →Performance of consumer wrist-worn sleep tracking devices compared to polysomnography: a meta-analysis
Lee et al., 2025 · Journal of Clinical Sleep Medicine
The most comprehensive recent meta-analysis of consumer wrist-worn sleep trackers vs PSG: 24 studies, 798 patients, 12 different brands including Fitbit, WHOOP, Garmin, Apple Watch, Empatica E4, and Xiaomi Mi Band 5. Headline finding is that across the entire device set, consumer wrist trackers UNDERESTIMATE total sleep time by ~17 minutes (95% CI -26 to -7) and UNDERESTIMATE sleep efficiency by ~4.7 percentage points, both statistically significant. This is the strongest published quantitative answer to the question 'how wrong are consumer trackers on average' across the wrist-worn category. Important limit: pooled across brands, no per-device breakdown extracted into this record.
Quality of Sleep Data Validation From the Xiaomi Mi Band 5 Against Polysomnography: Comparison Study
Concheiro-Moscoso et al., 2023 · Journal of Medical Internet Research
The most directly relevant published validation for any Xiaomi Mi Band generation. Tests the Mi Band 5 (released 2020) against PSG in a clinical population. The 78% accuracy / 89% sensitivity / 35% specificity / kappa 0.22 figures should NOT be extrapolated to the Smart Band 9 because the underlying sensor (BioTracker generation, processing algorithms) has changed. CircaTest cites this as the only published peer-reviewed Xiaomi-family validation, with the explicit caveat that newer generations require their own validation.