Eficiência do Sono (TST/TIB)

Sleep efficiency (TST/TIB)

Sleep efficiency compares Total Sleep Time (TST), the minutes you are actually asleep, against Time in Bed (TIB), the minutes between lying down and getting up. The formula is efficiency = TST / TIB × 100%. Take an example: 420 min asleep across 480 in bed works out to 87.5%. As for where you stand, >85% is good and >90% is excellent, while <80% points toward insomnia and is one of the criteria for recommending CBT-I (cognitive-behavioral therapy for insomnia, the first-line treatment). To measure it properly the gold standard is polysomnography (PSG) with EEG, EOG, and EMG, run at a sleep lab.

Applications

It shows up when diagnosing insomnia and apnea, in home oximetry monitoring, in screening before bariatric surgery, and in tracking through wearables. The Apple Watch, Garmin, Oura Ring, and Fitbit all estimate TST from movement and heart rate, and they tend to overestimate by roughly 10–20% next to PSG. It also helps you set bedtime in sleep restriction therapy, where TIB is widened bit by bit until efficiency clears 90%.

FAQ

Is the watch reliable? It is decent for spotting trends, but it won't replace PSG when you need a diagnosis. Its read on deep sleep and REM is limited.

What is sleep latency? It is how long you take to fall asleep, and 10–20 minutes is about right. Dropping off in under 5 minutes usually means you are sleep deprived.

Why is efficiency low without insomnia? Long stretches in bed reading or on your phone drag the ratio down. Keep TIB close to what you actually sleep.

And in the elderly? With age, efficiency drifts down to 75–85% on its own because awakenings get more frequent. Factor age in when you read the number.