As an elderly guy of 70 years having some trouble sleeping, I decided to get an Inspire 2 Fit-bit to track my sleep. My first night sleep showed I had only slept about 4 hours starting in the early morning hours giving me a fair rating, although I would consider 4 hrs to be poor. Assuming the watch needs to calibrate for a period of time, I found that the second night seemed to record properly with about 7.5 hours sleep giving me a good score. The 3rd night was not rated as a good night and the unit recorded several chunks of sleep instead of combining them into one chunk for the night. The following night the unit again divided my sleep into 2 different chunks. I don't know why it does this. I've programmed my sleep start at 10:45pm and end time for 7:30am for 7 days a week, both in the watch and in the app. I would think that the Fit-bit sleep chart and score would be calculated based on these time settings even if the person was up during the night for a bathroom break. The sleep chart should then show this as an awake period at that particular time. When the unit divides my sleep time into 2 or more chunks, I have to edit the time assigned after the fact for that sleep period. The Fit-bit forums suggested I change the sleep sensitivity from "sensitive" to normal but I found out that the sleep sensitivity setting is already set at "normal". I was able to get the full sleep period by deleting the incomplete sleep logs for the night and entering it manually. Make sure to enter the start date first followed then by the correct AM or PM time followed then by the end date and time. The app will get confused if you mess up on this and it may then leave a simple chart with no score, however you can delete it and try again. The unit is a bit too thick to allow me to lay my arm comfortably under the pillow when sleeping but I've learned to adjust for that. Battery life is excellent as mine went a week and still had about half the charge. I've noticed my phone battery was draining significantly quicker due to the Bluetooth usage, so I prefer to have the unit gather data for a day, using a one-time per day sync in the morning. This would however, effect it's notification options from your phone. I sacrificed these functions and simply closed the phone app and turn off Bluetooth on my phone except to sync the unit.
I have now used this for over a year and although I'm able to combine 2 or more chunks to get a sleep score, I sometimes have to delete recorded sleep time in the evening while watching TV or at the computer. If the unit thinks I'm asleep during those times, might it also think I'm asleep in bed when I'm really not? My particular biology might be out of the normal to result in these records. My scores are typically around 78-82 with a high score of 90 (excellent) and a low of 59 (Poor). The 59 score was below my age margin for REM sleep and deep sleep and was likely due to supplement adjustments or something out of the ordinary.
Although the technology of this device is quite remarkable, don't fall into a trap thinking this device is a highly accurate display of sleep data. The anxiety created from receiving an undesirable score may actually harm your sleep. My wife would keep telling me to quit relying on it so heavily. I am now to the point that if I have forgotten to put it on for the day or evening when I go to bed, I will just shrug it off and not worry about it. This watch is quite an example of engineering but remember it's inherent limits in gathering data. It can't monitor your brain waves but makes sleep interpretations based on data from it's sensors, comparing it to a database of common readings for your age group which may or may not be close to your actual results. Just remember that it is a tool to help you and it is best used to show your personal trends from day to day. It's likely more useful in checking your movements and heart rate during the day. After all, it is called a "Fit" bit and not a "Sleep" Bit and since sleep can be related to exercise, I have begun to focus more on the exercise data from the unit.
If you are trying to make adjustments to improve your sleep or any other section of the Fit-bit program, it would be nice if there was a place to enter notes for each day/night that could be reviewed as needed? (thunderstorm that night, sick, etc.) This lack of a personal daily notes section is a shortcoming in my opinion. Check my other reviews and may God help you in your quest for good sleep.