Respiratory rate on wearables: one of the steadiest numbers you track
Overnight breathing rate barely moves in healthy people. That is what makes a change useful. Here is how devices measure it and what the illness studies found.
Respiratory rate is breaths per minute. Most people never think about theirs. Wearables report it each night, and for good reason: in healthy adults it is one of the most stable physiological numbers there is, so a rise stands out.
How a ring or watch measures breathing
Most wearables do not sense the chest moving. They infer breathing from the heart. Each breath in speeds the heart slightly and each breath out slows it, a pattern called respiratory sinus arrhythmia. A 2021 paper from Fitbit researchers explains the method: isolate that rhythmic component from the beat-to-beat interval data, and its frequency is the breathing rate. Against a validation dataset from sleep studies, their estimate had a mean absolute error of 0.46 breaths a minute and a mean absolute percentage error of 3 percent.
That method needs clean beat-to-beat data, which is why devices report respiratory rate for sleep rather than during the day. WHOOP's 2020 paper likewise describes respiratory rate taken from the wrist strap during night-time sleep, and the illness model built on it used changes in that nightly figure rather than any single reading.
Normal overnight values
| Finding | Value |
|---|---|
| Mean overnight rate, healthy adults | 15.4 breaths/min |
| Range covering 90% of healthy adults | 11.8 to 19.2 breaths/min |
| Sex | Higher in women than men under 50; no difference after 50 |
| Age | Decreases slightly with age |
| Body mass index | Lowest at a BMI of about 25, higher above and below |
| Heart rate | Rises with nocturnal heart rate |
| Night-to-night variation (14 days, 90% range of the coefficient of variation) | About 2.3 to 9.5% at ages 20 to 24; about 2.5 to 21.7% at ages 65 to 69 |
That last row is the key. For a young adult, night-to-night variation is usually under 10 percent. So a rise of two or three breaths a minute above your usual level, held for more than a night, is a real change and not noise.
What the illness studies found
| Study | Year, journal | Who and how many | Design | Main result |
|---|---|---|---|---|
| Miller et al. | 2020, PLoS One | 271 WHOOP users with COVID-like symptoms; 81 tested positive | Model built on changes in nightly respiratory rate | Identified 20% of positive cases in the two days before symptom onset and 80% by the third day of symptoms (authors include WHOOP employees) |
| Natarajan et al. | 2021, npj Digital Medicine | Fitbit users with COVID-19 | Window from one day before to five days after symptoms or test | 36.4% of symptomatic and 23.7% of asymptomatic people had at least one night 3 breaths/min above their usual rate (authors employed by Fitbit) |
| Mason et al. | 2022, Scientific Reports | 63,153 Oura users; 73 PCR-confirmed cases used for training | Multi-signal model including temperature, heart rate, HRV and respiratory rate | Detected COVID-19 an average of 2.75 days before testing, sensitivity 82%, specificity 63% |
These were early-pandemic studies, mostly built by or with the device makers, and none is a diagnostic test. They show that respiratory rate is a sensitive general sign that something is going on, often infection. They do not show it can tell one illness from another, or that it catches most cases early: the Fitbit data found the 3-breath rise in only about a third of symptomatic people.
How to read your own number
- Learn your range first. Two to three weeks of nights gives a usable baseline. Most healthy adults sit somewhere between 12 and 19 breaths a minute at night, but your own figure matters more than the population one.
- Look for a sustained rise. In the Fitbit COVID-19 analysis, the signal was a night 3 breaths a minute above the usual rate. A single night at +1 is within normal variation for most people.
- Expect more variation with age. The upper end of normal 14-day variation more than doubled between ages 20 to 24 and 65 to 69.
- Read it with resting heart rate and temperature. Several signals moving together is more convincing than one.
Inside the WHOOP study
The 2020 WHOOP analysis drew on 2,672 days of data from 271 people: 1,856 healthy days, 231 days while infected with COVID-19, and 585 days with symptoms but a negative test. The model was trained on 57 people who tested positive and checked on a separate 24 positive cases and on 190 people who tested negative despite symptoms. That last group matters, because a useful signal has to separate COVID-19 from other causes of feeling unwell. The model was examined over a six-day window around symptom onset, so it says little about how often it raises false alarms in everyday life.
Other reasons it rises
- Fever and infection, the main reason.
- Altitude. Breathing rises at altitude as the body compensates for lower oxygen.
- Alcohol raises overnight heart rate, and respiratory rate tends to move with nocturnal heart rate.
- Hard training and heat.
- Lung or heart conditions. A persistent rise with breathlessness, cough or chest symptoms needs a clinician, not a trend line.
How the scores use it
WHOOP lists respiratory rate as an input to Recovery. Garmin lists respiration rate among the signals behind its Sleep Score. In each case it is judged against your own baseline.
Logging it
Peptide AI pulls overnight respiratory rate where the device provides it, through wearable integrations, and flags readings outside your baseline. Seeing it next to resting heart rate and HRV on one timeline, with the dose log underneath, helps separate "I am getting ill" from "I changed something".
Questions people ask
What is a normal respiratory rate during sleep?
In healthy adults measured by wrist wearables, the mean overnight rate was 15.4 breaths per minute, and 90 percent of values fell between 11.8 and 19.2.
How do wearables measure breathing rate?
Mostly from the heart. Breathing speeds and slows the heart rhythmically, and devices extract that frequency from beat-to-beat data. One validated method had a mean absolute error of 0.46 breaths per minute.
Can respiratory rate detect illness?
It often rises during infection. In a 2020 WHOOP study it identified 80 percent of COVID-19 cases by the third day of symptoms, but it is not a diagnostic test and does not identify the cause.
How much variation is normal?
Little. For adults aged 20 to 24, 90 percent had a 14-day coefficient of variation between about 2.3 and 9.5 percent. A sustained rise of 2 to 3 breaths per minute stands out.
Sources
- Measurement of respiratory rate using wearable devices and applications to COVID-19 detection (Natarajan et al.), npj Digital Medicine, 2021
- Analyzing changes in respiratory rate to predict the risk of COVID-19 infection (Miller et al.), PLoS One, 2020
- Detection of COVID-19 using multimodal data from a wearable device: results from the first TemPredict Study (Mason et al.), Scientific Reports, 2022
- WHOOP 101, WHOOP developer documentation
- New data examines quality of Garmin users' sleep, Garmin, 2023
- Acute effect of alcohol intake on cardiovascular autonomic regulation during the first hours of sleep in a large real-world sample of Finnish employees (Pietila et al.), JMIR Mental Health, 2018
