Apple Watch Series 12 and Garmin Cirqa Match Readiness After Week of Sleep Tracking

Apple's Vitals app uses heart rate variability, respiratory rate, blood oxygen and other data to establish a user's typical range. After seven nights, the app can assess whether those measurements fall outside that range. Readiness aggregates sleep quality based on those parameters, compares it with activity levels and produces a score from 1 to 10. Because Apple's feature is new, the writer expected the two devices to produce very different scores at first and then converge as Apple learned more about the body.

The first night produced a sharp split. Apple gave a sleep score of 93, while Garmin gave 62. After that, the scores followed the same general trend: a rising incline through the week, a dip in the middle and a high final night. One major outlier came on the sixth night, when Garmin gave 87 and Apple gave 68. TechRadar published the nightly scores as follows: Sept. 26, Garmin 62 and Apple 93; Sept. 27, 67 and 56; Sept. 28, 78 and 82; Sept. 29, 95 and 84; Sept. 30, 77 and 72; Oct. 1, 87 and 68; and Oct. 2, 87 and 83.

TechRadar cited research from health data API creator Terra, which measured 77,000 nights of sleep across six major wearables companies. The research found that most trackers are accurate enough to converge on duration and general trends, but outliers can appear because manufacturers use different sensors and algorithms. According to the study, "once you break sleep into stages [light, deep, REM phases of sleep], agreement [between wearables] falls apart: REM, deep, and light can diverge by hours in direct comparisons." The article asked whether such outliers are statistically important as long as the wearables chart similar trends and reach the same conclusions.

At the end of the week, Apple gave its first Readiness score: 7 out of 10, indicating the writer was ready without being fully prepared for a large workout. The Garmin Connect app showed a Readiness score of 70 out of 100. TechRadar reported surprise that the two devices reached the same conclusion after a week of constant wear despite earlier discrepancies. Both also produced a similar-shaped sleep score graph, which the writer took as a sign that they are internally consistent and generally quite accurate.

The writer concluded that either device would be acceptable for tracking sleep, Readiness and fitness in general terms. The differences in individual data points, however, were a reminder not to get too caught up in the data, because the devices are imperfect and estimate. If users stress too much over scores or feel differently than their watch says they should feel, the article advised prioritizing the body's messages over the wearable's and not being afraid to get an untracked night of sleep. It also noted that differences appeared in a separate Apple Watch Series 12 versus Garmin Fenix 9 Pro test.