I've experienced the same thing and my research on the problem has led me to the knowledge that physicians (their field of medicine being that of sleep study specialists) have pointed out that a simple device utilizing only movement as a measure of the quality and type of sleep you experience isn't going to be accurate because there has to be a measurement of electrical brain wave activity as well, which is achieved in a medical sleep study with electrodes during a medical sleep study to record your brain activity. Therefore, the wrist Fitbits will never be an accurate measurement of the quality of sleep you get, it only will measure by the amount of movement you have. I too wanted to measure the quality of sleep I got and was not happy when I researched and found this information from medical doctors, but, on reading it understand the information as being accurate because of my personal experience with have had multiple sleep studies performed and yes, electrodes are utilized for accurate measurement of brain activity. They do use movement measurements of course, but there are other factors that must be measured and considered for an accurate measurement of the quality of sleep an individuals sleep. Therefore, the maker's of Fitbits are mis-representing their products by stating they can measure the quality of an individuals sleep. Shame on them. I am keeping my Fitbit and do look at my sleep results because it does tell me how much I am moving around, I think that helps me understand how restless I am, ergo how well I am sleeping, but it isn't an accurate measurement of whether or not I am in REM, light or deep sleep as the different stages of sleep.
