Earlier this week Apple announced some of the new health features we will see in watchOS 8 when it is released in August/September. One of the new features of the native Sleep App is that it records the respiratory rate on the Apple Watch whilst sleeping.
In itself, this appeared to be singularly UNinteresting. After all, many of Apple’s competitors already produce respiratory rate data along with other health-focused metrics including HRrest, HRV/SDNN/rMSSD and SpO2. I believe I’m right in saying that subtle variations in optical HR recording are used to determine when a breath is taken. So I initially imagined this was yet another case of Apple coming along a little bit late to the party, perhaps with a slightly better sensor (ie the AW6 HR sensor) and then, as a result, producing slightly more reliable data.
The interesting news here is that Apple has taken a different approach as their press release pointed out
Today, Apple Watch helps users meet their sleep goals by establishing a pre-bedtime routine, and tracks metrics like time asleep, heart rate, and blood oxygen. watchOS 8 gives users even more insight into their overall wellness by tracking sleeping respiratory rate, which is the number of breaths per minute. To do this, Apple Watch uses the built-in accelerometer to measure respiratory rate while sleeping…
After a little digging around it seems that the new sensor readings are taken at 50Hz ie fifty times a second and that these readings make assessments of tiny bodily movements that can be quite accurately correlated with the true respiratory rate which is easily validated by independent sensors.
Q: So why is this better?
A: try this
- individual readings may or may not be more accurate than those based on HR (TBC), but there should be a MUCH greater number of these readings and I would guess that overall accuracy is improved because of a greater sample size
- Apple can then give an almost constant nightly feed of respiration data. ie FAR more data points for app developers to work with. This may QUICKLY allow the detection of some unwanted sleep events and triggering exception conditions/alerts.
- Apple currently only takes 2 or 3 nightly HRV readings (unchanged in watchOS 8 so far) and the infrequency of this data limits its usefulness. The respiration data is more frequent and potentially more useful as a result.
The two main thrusts for this data are towards early onset detection of illness (covid) and Sleep Apnea events. So these are HEALTH-focussed features rather than fitness focussed.
The trick, I believe, is going to come in making a valid fusion of the respiratory data with other health data sets. So an algorithm for detecting upcoming illness might look something like this – increased respiration rate above the 30-day average, SpO2 falls 1%age point below normal and HRrest rises by 5bpm independently of workout stress….something like that. ie not straightforward.
Fitness Take Out
Sadly there is no fitness and athletic take out here. Other than it’s always good to know if you are going to get ill. To get more useful sporting recovery metrics from the Apple Watch we still need MORE automatic nightly recording points please Mr Cook (Apple CEO).
Science link: ncbi.nlm.nih.gov/pmc/articles/PMC7471298/#CR1 “There is substantial evidence that deviations of the respiratory rate from its normal behaviour can be used as a predictor of clinically relevant and potentially fatal events and conditions (see, e.g., the very recent review paper by Liu et al.1 and references therein)” and ncbi.nlm.nih.gov/pmc/articles/PMC7471298/, shows the validity of Apple’s approach.
Thank you: DanielH & MarkusE for the heads up and pointers.
Recommended Reading: Apple Watch 6 Longterm Review